Review Article

THE USE OF IMMUNE SYSTEM CELLS FOR THE TREATMENT OF METASTATIC CANCER: A PERSONALISED MEDICINE CONCEPT

Ebenezer Olaleye Olajuyin1,*Olorunfemi Ayeotan2, Kehinde Sulaimon Ayinde3, Tioluwani Victor Olubiyi4, Ilerioluwa Gabriel Oke5, Olajumoke Saidat Aluko6

1) Department of Medical Laboratory Science, Federal Medical Centre, Makurdi, Nigeria.2) Department of Medical Laboratory Science, University College Hospital, Ibadan, Nigeria.3) Institute of Biology, State University of Campinas, Campinas, SP, Brazil.4) Department of Medical Laboratory Science, State Specialist Hospital, Asubiaro, Osogbo,

Nigeria.5) Department of Medical Laboratory Science, National Hospital, Abuja, Nigeria.6) Department of Medical Laboratory Science, University of Osun Teaching Hospital, Osogbo,

Nigeria.

Correspondence :

OlorunfemiAyeotan , Department of Medical Laboratory Science, University College Hospital, Ibadan, Nigeria, femiayeotan@gmail.com

Abstract

Cancer is initiated by an alteration or mutation of genes which may occur naturally i.e. inherited or

acquired over the years as a result of environmental factors or by exposure to certain chemicals

(carcinogens), exposure to various forms of radiations and lifestyle habit such as smoking ,alcohol,

poor diet and obesity. During cancer progression, various components of the innate and adaptive

immunity are activated in effort to reduce or remove the cancer mediated inflammation but tumour

cells avoid the immune attack posed by these cells. Various cancer cells have unique mechanisms

through which they escape from the immune response making them resistance to destruction by the

immune system. In effort to treat various forms of cnacers, scientists have been able to device means

by which the immune system can be modified in other to fight cancer cells, this form of treatment that

focuses on the modification of the innate and adaptive immune system in treatment of cancer is

termed immunotherapy.

Keywords: Cancer, Immunotherapy, Immune system, tumour, personalised medicine

INTRODUCTION

Cancer is a multigenic disease that can arise from all existing cell types (stem cells, red blood cells,

white blood cells, platelets etc) and organs with a multi-factorial etiology. It is the second leading

cause of death globally according to the World Health Organization (2018). About 12.7 million cases

of cancer are reported per year worldwide with the United Kingdom accounting for about 363,000

cases of cancer yearly (International Agency for Research on Cancer, 2008, Cancer Research UK,

2016).

Cancer is initiated by alteration or mutation of genes which may occur naturally i.e. inherited or

acquired over the years as a result of environmental factors, exposure to certain chemicals

(carcinogens), exposure to various forms of radiations, lifestyles not limited to smoking , drinking etc.

Hanahan and Weinber described six hallmarks of cancer which include; cells with unlimited

proliferative potential, environmental independence for growth, evasion of apoptosis, angiogenesis,

invasion and metastasis to different parts of body. An updated version of the Hallmark of cancer

described by Hanahan and Weinber in 2000 further classify the hallmark of cancer into Seven due to

clear understanding of tumorigenesis in recent times (Fouad and Aanei, 2017).

In a normal cell, DNA replication and cell division is well coordinated and regulated by the process of

the Cell division cycle. In the cell cycle, control mechanisms include cascade of protein

phosphorylation involving highly coordinated kinase family whose function is to direct cells from one

stage of the cycle to the next. Kinases becomes activated when they bind with cyclin which are

proteins produced at specific stages of the cycle thereby activating the Cyclin dependent Kinases

(CDK)responsible for Transcription regulation, mRNA processing and differentiation(Morgan,1995).

During cancer progression, various components of the innate and adaptive immunity are activated in

effort to reduce or remove the caner mediated inflammation (Dunn et al., 2006; Chen and Mellman

2013). Tumor cells cunningly avoid the immune attack posed by this cells using two main strategies

which are avoiding the immune recognition and instigating an immunosuppressive tumor

microenvironment (TME). Cancer cells have the ability to lose the expression of tumor antigens on

their cell surface which makes it difficult for the cytotoxic T-cell to recognize them. For instance

about 40% of non-small cell lung cancers (NSCLC) hold a loss of heterozygosity in human leucocytes

antigen (HLAs), which eventually leads to immune escape by presenting only a small number of

antigens (McGranahan et al., 2017). The resistance to T-cell transfer in metastatic colorectal cancer

and poor outcome of the response to checkpoint blockade immunotherapy in both lung and melanoma

cancer patient has also been associated to loss of HLA (Tran et al.,2016; Chowell et al., 2018). In this

respect, alteration and omission in gene- arrangement may result in down regulation of the antigen

presenting machinery of which this may confer resistance to T-cell effectors molecule such as the

IFN-γ and TNF-α (Patel et al., 2017).

Tumor cells has the capacity to instigate an immune tolerant tumor microenvironment, they achieve

this by expressing some inhibitory checkpoints blockade molecule such as CTLA-4, PD-L1 and V

domain immunoglobulin suppressive T- cell activation (VISTA) ( Topalian et al., 2012; Snyder et

al., 2014; Boger et al., 2017), secretion of some immunospressive molecules such as VEGF, TGF-β,

prostaglandin E2 and IL-10 (Gabrilovich et al., 1996; Massague, 2008; Dominguez- Soto et al., 2011;

Bottcher et al., 2018) and initiation of the recruitment of MDSCs, TAMs and Tregs by tumors-

derived chemokines such as CCL2, CCL5, CCL22, CXCL5, CXCL8, and CXCL12 (Weitzenfeld and

Ben-Baruch 2014; Kumar et al., 2016; Mantovani et al., 2017; Tanaka and Sakaguchi 2017).

Combination of all this strategies makes it easy for tumor cells to escape the action of the immune

system.

The concept that the immune system can be influenced and modified to counter and fight neoplastic

antigens have been in existence for a very long time, this concept is refer to as immunotherapy (Ichim,

2005). In year 1777, the great surgeon Duke of Kent first contributed to the development of cancer

vaccine, he did this by injecting himself with malignant tissue as a prophylaxis against cancer cell

growth and development. (Coley, 1891). Another great contributor to immune system modification

and manipulation in other to produce vaccine is that of Louis XVII who inoculated himself with

breast cancer tumour cells with the hope of reversing soft tissues sarcoma. With all this effort, there

was no major success recorded not until the year 1891 when a clinician at the memorial Sloan

Kettering Cancer Institute in New York used heat killed endotoxin- contain bacteria (streptococci and

serratia marseceus) to cure soft tissue sarcoma (Wiemann and Starnes, 1994).

This review describes the current and evolving finding that contributes to the field of

immunooncology, as well as the important of immunotherapies as a potential treatment method for

cancer.

CANCER IMMUNOTHERAPY AND PERSONALIZED MEDICINE.

According to the data released by National Cancer Institute (NCI) in 2016, about 1.6 million cases of

newly diagnosed cancer cases were recorded that year alone (Siegel et al., 2016). With this high

increase in the number of cancer cases, it is imperative to provide a more effective treatment to halt

the progression or completely cure cancer disease.

Over the past decades, various studies have shown clearly that no two patient’s cancer are the same

and hence may have variable response to genetic treatment (Burney et al., 2017). As understanding of

complexity and distinctiveness of each neoplastic cell have greatly improved, the propriety of a

singular therapeutic intervention for the cure of cancer should be questioned (Laura et al., 2017). An

effective model aimed to change this ‘one-size –fits –all’ approach is based on personalized and

precision medicine (PPM) (Williams et al., 2015). Personalized medicine has significantly improved

Overall Response (ORR) and Overall Survival (OS) rates of cancer patients (Laura et al., 2017). It

involves the development of a specialized treatment for each specific subtypes of neoplastic disease,

based on the quantification and manipulation of the patients genetics and patients ‘omic’ data

( metabolomics, proteomics, transcriptomics ) (Paulina et al., 2018).

Omics technology has contributed immensely to the characterization of various molecular changes

that underlie the development and continuance of a wide range of complex human disease, including

cancer. This technology has contributed greatly to the advancement of precision medicine (Oliver et

al., 2019). Beginning with the field of genomics, the investigation and rapid elucidation of the entire

human genome once and for all, not having to undergo gene by gene analysis has now become more

fascinating and cost effective due to development of this novel sequencing technology (Yadav, 2007).

Genome sequence information has helped to diagnosed patients; predict individual risk for developing

a disease and also to assess whether a particular treatment option is suitable and successful in an

individual patient (Oliver et al., 2019).It focus on DNA sequencing to recognize cancer-specific

mutations (inheritable and spontaneous cancers) and examine chromosomal re-arrangement to

characterize subtypes of cancer (Tomczak et al., 2015).

For better characterization of tumor cells abnormalities, other advanced omics technologies have been

applied to tumor and cancer samples in the past several years and this are beginning to contribute

greatly a better understanding to the molecular mechanism of various diseases. One of this advance

technology is transcriptomics, the study of the expression of all genes contains in a cell or in an

organism. Genetic research has extensively used this approach to outline and quantitatively analyze

all the transcriptomes of cells and tissues and determine how changes that occur in gene transcription

can be used to distinguished disorders and recognized the molecular mechanism underlying the

disease development and progression (Oliver et al., 2019). At present, almost 800,000 gene

expression database related to malignant tumors has been deposited in the Gene Expression Omnibus

(GEO) of NCBI of NIH. In addition, TCGA has also make use of transcriptomics technology to

provide a detailed gene expression examination of individual tumors and tissues from more than 1,000

patients (Weinstein et al., 2013).

Proteomics helps in the analysis and quantification of cellular proteins ( Aebersold and Mann, 2015)

which are the translational product of RNA transcript and the principal mediator of all cellular

functions. TCGA consortium was the first large-scale effort to outline the tumor proteome in cancer

proteomics, this analysis was performed using reverse protein arrays and was limited to only the

target protein, about few hundreds of them. However, several studies have used avant-grade

spectrometry approach to detect tumor specific biomarkers in gynecological cancer (Swiatly et al.,

2018) and also use proteomics data in classification of breast cancer.

The analysis of small molecules present in cells, tissues or fluid has been the main focus of biomarker

discovery studies for decades and this has been achieved by metabolomics. The products of cellular

processes mediated by protein are metabolites. Changes in this metabolite are presumed to be changes

in function of the mediated enzymes and proteins. Majority of metabolomics have focused in the

analysis of patient’s serum and plasma for possible detection of biomarkers that can be used in cancer

diagnosis without invasive tumor biopsy sample. Metabolomics has been used in detecting serum

diacetylspermine (DAS), a diagnostic maker for non-small cell lung cancer (NSCLC) (Wikoff et

al., 2015).

Immunotherapy is the field of immunology that aims to identify treatments for diseases through

induction, enhancement or suppression of an immune response. Various cancer cells have unique

mechanisms through which they escape from the immune responses making them resistance to actions

of the immune system (Schreiber et al., 2011). In effort to treat various forms of malignancies,

scientists have been able to device means by which the immune system can be modified in other to

fight cancer cells, this form of treatment that focus on the modification of the innate and adaptive

immune system in treatment of cancer is called immunotherapy (Mellman et al., 2011).

The significance of immunotherapy was acknowledged in year 2008 when James Allison and Tasuku

Honjo won the Nobel prize in medicine as a result of their work, where they discovered cytotoxic T-

lymphocyte associated protein (CTL-A) and programmed cell death ligand 1 (PD-1/PD-L1)

respectively (Altmann et al., 2018).

Cancer immunotherapy can be categorized into various types such as: cytokines, cancer vaccines,

monoclonal antibodies (mAb), small molecules and autologous T- cell (Adams et al., 2015). The type

of therapy to be used depends on cancer types and their location (Pankita et al., 2016).

Major categories of immunotherapy and their mechanisms

Oncolytic Virus Therapies

The form of immunotherapy that uses viruses to infect and destroy cancer cells is known as oncolytic

virus therapy. Cervical cancer and Head and neck cancer is associated with human papiloma virus,

while hepatocellular carcinoma (HCC) is caused by the inflammatory action of hepatits B virus

(HBV) on the liver hepatocyetes. Various vaccines have been discovered for preventing the action of

these cancer causing viruses (Schiller et al., 2010). Oncolytic virus therapies rely on genetically

modified viruses in other to infect neoplastic cells, and thus they encourage a pro- inflammatory

environment to increase systemic antitumor immunity (Orange et al., 2016, Russell et al., 2012). The

current advancement in DNA cloning and virus modification technologies, oncolytic virus therapies

have recorded major progress in recent years. For example Talimogene harparevec (T-Vec) which is

also known as lmlygic, a genetically modified herpes simplex virus has been approved by the FDA for

the treatment of metastatic melanoma (Andtbacka et al., 2016)

Talimogene harparevec is a double stranded herpes simplex virus with deletion in the ϒ34.5 and α47

genes. The deletion in the ϒ34.5 gene is responsible for cancer selective replication and attenuate

pathogen (Chou and Roizman, 1992). The deleted loci are replaced by GM-CSF gene (Hu et al.,

2006). The original function of the deleted ϒ34.5 gene is to negate the host cell’s shut-off protein

synthesis upon viral infection (Markert et al., 2006) but once deleted it renders the virus unable to

replicate in a normal cell. The deletion of α47 genes relive the virus of it function to antagonize the

host cell’s transporter associated with antigen presentation. It deletion precludes the down regulation

of Major histocompatibility complex class I expression which should amplify immune response

(Goldsmith et al., 1998).

Pexastimogene-devacirepvec, Pexa-Vec (JX, 954) is a genetically modified vaccinia virus which was

originally discovered by edmuid lattime’s laboratory at Thomas Jefferson University. It was

engineered by the deletion of TK gene and replaced it with the GM-CSF which limits the viral

replicative ability. It also consists of a LacZ gene insertion as a marker (Parato et al., 2012). The

benefit of using vaccinia virus includes strong cytotoxicity of the virus, Intravenous stability for

delivery and extensive safety experience as a live vaccine (Kirn and Thorne ,2009).

Cancer vaccines

Cancer vaccines use tumour specific antigens (TSA) to activate T-Cell mediated anti-tumour

feedback. The first validation of active immunotherapy for treatment of neoplastic diseases was the

approval of provenge (sipuleucel-T) by the US food and drug agency (FDA) in year 2010 for the

treatment of prostate cancer (Mellman et al., 2011). It is a form of autologous cellular immunotherapy

which consist of granulocyte macrophage colony stimulating factor (GM-CSF), peripheral

mononuclear cells, and immuno surveillance of cancer antigen- prostatic and acid phosphatise (PAP)

(Cipponi et al., 2011). The mechanism of action includes activation, differentiation and initiation of

effector function of the T-cell, This occurs when the PAP taken up by the antigen presented cell

(APCs) is presented to the T-cell (Cipponi et al., 2011). The GM-CSF helps in stimulating the growth

of APC such as macrophages (Shi et al., 2006). Another cancer vaccine is GVAX, an irradiated and

autologous pancreatic cancer vaccine which consist of genetically modified patient pancreatic cells, it

aim at triggering the secretion of GM-CSF (Dranoff et al., 1993). It has been shown to augment the

tumor- specific immune response in cancers (Salgia et al., 2003).

Adoptive T-cell therapy

Adoptive T-cell therapy utilizes autologous immune cells, most especially T-cells which are

extracted, genetically modified, in vivo amplified and re-injected back to the patient in other to

eliminate cancer cells (Lee et al., 2016).

Recently, chimeric antigen receptor T-cell (CAR-T cell) has gained attention from their clinical

success. In this CART- cell approach, T-cell are collected from patient blood, they are genetically

engineered to express CARs that are specific for the antigen present on the cancer cell and are

administered back to the same patient (Rachel et al., 2019). Once the CART gene is injected into the

patient, it recognizes the tumour cells and induced tumour cell death (Lim and June, 2017). A new

CAR-T cell therapy called brexucabtagene autoleucel (Tecartus) was approved by US FDA on 24th of

July 2020 for the treatment of mantle cell lymphoma, a fast growing cancer of the blood that has been

difficult to treat over the years. A Large percentage of people living with this disease are diagnosed

with aggressive form of the disease. A clinical trial accessing ZUMA-2, a CAR-T therapy was

approved by the FDA. In this trial, brexucabtagene was tested on 60 patients suffering from mantle

cell lymphoma, who had received some prior treatment in time past. 87% of patients that undergone

this trial responded to a single infusion of brexucabtagene, while 62% of the patient had a complete

response. All patients that participated in this trial were initially treated with a drug that blocks the

activity of bruton `s tryosine kinase (BTK), a protein that facilitates the growth and

development of neoplastic cells.

Immune checkpoint inhibitors

Despite the major succeses recorded in adoptive T-cell therapies, a recently developed class of

monoclonal antibodies (mAbs) (Scott et al., 2012), immune checkpoint inhibitors (ICIs) are gaining

more recognition in medical practice and have become one of the most successful immunotherapies.

Ipilimumab was approved by the FDA in 2011 for the treatment of melanoma, it is a monoclonal

antibody that targets CTLA-4 on the T-cell.it inhibit the suppressive activities of CTLA4 on the T-cell

thereby allow full activation of the T-cell for immune response against neoplastic cells (Chambers et

al., 2001). Ipilimumab is also known to inhibit the immunosuppressive activity of Tregs (Mellman et

al., 2011). Similarly, pembrolizumab (Keytruda) is an IgG4 monoclonal antibody that inhibits the

suppression activity of PD-1 (Callahan et al., 2016). PD-1 is expressed on the T-cell and play the role

of suppressing the immune action of T-cell, treatment with the use of keytruda prevent the inhibitory

activity of PD-1 hence activation of T cells (Aris and Barrio, 2015). It was approved by the FDA in

September 2014 for the treatment of melanoma and also approved for the treatment of non-small-cell

lung cancer (NSCLC) in October 2015 (Lee1 et al., 2016). Nivolumab (Opdivo) is also an IgG4

monoclonal antibody, it targets anti- PD-1 in melanoma, renal cell carcinoma and squamous non-

small-cell lung cancer patients (Callahan et al., 2016). Nivolumab function in the same manner as

Keytruda (Aris and Barrio, 2015) because they are both anti PD-1 immunotherapies, they facilitate

ADCC and this result to death of cancer cells (Chen and Mellman, 2015). In the past years, some

biotech company has put in efforts to develop potent monoclonal antibodies against the ligand for PD-

1, PD-L1, as another means to inhibit the suppressive activity of PD-1 in certain cancers (Chen and

Mellman, 2015).

Cytokines

Another immunotherapeutic approach embrace for cancer treatment is the use of cytokines or small

molecules (Pankita et al., 2016). They are the first class of immunotherapy introduced to medicine

with the approval of IFNα therapies in 1986 (Thomas et al., 1986) The mechanism of action of

cytokines is different from that of check point inhibitors because injected cytokines stimulate the

direct growth of immune system cells. They increase the activity of the immune system. Interferons,

interleukins and granulocyte-macrophage colony stimulating factor (GM-CSF) are the 3 types of

cytokines sought after in immunotherapy (Lee et al., 2011). Interferons are group of signalling

proteins which are normally produced by the immune cells in response to microbial pathogens. It

elicits immune by inciting the maturation of numerous immune cells such as NK cells, macrophages,

dendritic cells and lymphocytes (Müller et al., 2017). The activation of interferon can also inhibit

angiogenesis in tumour cells causing its death (Enomoto et al., 2017). Interleukin promotes the

development and maturation of T-cells (CD4+ and CD8+ cells) , B- cells and haemopoietic cells (Cox

et al., 2012). Finally the GM-CSF improves the immune response by promoting T-cells homeostasis

and supporting the differentiation of dendritic cells (Yan et al., 2017). Various cytokines have been

approved for the treatment of cancer, for example proleukin is an FDA approved IL-2 cytokine for the

treatment of melanoma and renal cancer (Mellman et al., 2011). The mechanism of action is based on

its ability to promote T- cell activation and activation of other immune cells that express IL-2

receptors (Nelson 2004). Through proleukin activation, the immune system is activated and this helps

in destroying cancer cells. (Mellman et al., 2011). Recombinant G-CSF which is known as Filgratism

has also been approved from the treatment of neutropenia in patients with certain form of leukaemia

(Buchsel et al., 2002). It binds to its corresponding receptors on neutrophil progenitor cells thereby

causing stimulation and activation of neutrophil (Buchsel et al., 2002). Increase neutrophil production

can help in cancer treatment as it mediate cytotoxic effect on cancer cells and therefore phagocytosed

the cancer cell (Murphy et al., 2008).despite this functions of neutrophil in cancer treatment,

neutrophil also has an important role in cancer pathogenesis as it enhance cancer metastasis(Gregory

and Houghton, 2011). Filgratism should be used in combination with other immunotherapeutic

agents (Buchsel et al., 2002).

The use of small molecules for cancer treatment has increase greatly over the years, small molecules

have great advantage over other biologics, this include oral bioavailability, greater penetration of

tumour cells and ability to cross the cell membrane (Weinmann, 2016).

Immiquiod, a TLR 7/8 agonist induce the secretion of pro inflammatory cytokines, induce Th1 cell

mediated activation of natural killer cells to eradicate cancer cells and also suppress Tregs action

(Adams et al., 2015). It has been approved for the treatment of basal cell carcinoma (Weinmann,

2016), metastatic melanoma and localized cell carcinoma (Read et al., 2017). Immiquiod in

combination with resmiquiod has yielded positive result in treatment of cutaneous T-cell lymphoma

(Rook et al., 2015). Despite the positive result obtained from this combination, administration of

TLR7/8 agonist has a potential severe toxicity as they can trigger a serious cytokine storm which has

the potential to be harmful and this has limited its clinical use (Weinmann, 2016).

Table 1: Selected US Food and Drug Administration (FDA) approved cancer Immunotherapies (Riley et al., 2019).

THERAPY TYPE APPROVED CANCER YEAR OF FIRST APPROVAL

Cytokines for lymphocyte promotion

Imiqumiod

Aldesleukin

Intron A

Stimulates the production of IFN-γ, tissue necrotic factor (TNF) and IL-12

Recombinant IL-12

Recombinant IFNα2b

Basal cell carcinoma

Renal cancer and skin cancer

Melanoma, Kaposi sarcoma, chronic myeloid leukaemia, hairy cell leukaemia.

2004

1992

1986

Roferon A Recombinant IFN α2a Melanoma, Kaposi sarcoma, chronic myeloid leukaemia, hairy cell leukaemia.

1986

Vaccines

Sipuleucel-T Autologous PBMLs activated with recombinant human PAP-GM-CSF

Prostate cancer 2010

Bacillus calmette-Guerin

Strain of mycobacterium tuberculosis variant bovis

Bladder cancer 1990

Engineered T-cells therapies.

Axicabtagene ciloleucel

CD19- specific CART cells Large B cell lymphoma 2017

Tisagenlecleucel CD19- specific CART cells B cell acute lymphocytic leukaemia and non- Hodgkin lymphoma.

2017

Oncolytic viruses

Talimogene laherparepvec

Checkpoint inhibitors

Durvalumab

Ipilimumab

Pembrolizumab

Nivolumab

Avelumab

Genetically modified HSV type 1 designed to replicate within tumor and produce GM-CSF.

PD-L1 mAb

CTLA-4mAb

PD-1 mAb

PD-1 mAb

PD-L1 mAb

Melanoma

Urothelia and non-small-cell lung cancer

Melanoma

Hodgkin lymphoma, advanced gastro cancer, head and neck cancer, non-small-cell lung cancer, bladder cancer.

Kidney cancer, bladder cancer, colorectal cancer, hepatocellular cancer.

Meike cell carcinoma and urothelia cancer.

2015

2017

2011

2014

2014

2017

CURRENT IMMUNOTHERAPHY UPDATE

From the first description of immune infiltrates in tumours by Virchow in 1863 up until now, there

has been a notable progression in the number of cancer immunotherapy discoveries and techniques

available. The most recent updates on cancer immunotherapy include chimeric antigen receptor

(CAR) T-cell therapy, cancer vaccinations and immune checkpoint blockade therapy (Mellman et al.,

2011, Voena et al., 2016). Strategies such as engineered T-cell therapy or the application of next-

generation sequencing to identify new tumour antigens are current approaches with great potentials in

cancer immunotherapy (von Rundstedt & Necchi, 2017).

In 2017, the first cellular cancer immunotherapy drug, tisagenlecleucel, was approved by the FDA,

followed in 2018 by the EMA approval of a second drug called axicabtagen-ciloleucel. Approval of

these medications was based on impressive response rates seen in the ELIANA trial (relapsed or

refractory)[r/r] in Acute lymphoblastic leukemia in paediatric patients or young adults treated with

tisagenlecleucel), JULIETH trial ([r/r] DLBCL, Tisagenlecleucel) and ZUMA-1 trial ([r/r] DLBCL,

axicabtagen-ciloleucel). Although sold under different brand names, both medications have been

approved to treat patients with acute lymphoblastic leukaemia (ALL, tisagenlecleucel) and diffuse-

large B cell lymphoma (DLBCL, tisagenlecleucel and axicabtagen-ciloleucel) (Neelapu et al., 2017,

Schuster et al., 2019).

Tisagenelecleucel is a second generation CAR which is directed by CD19. CD19 is majorly expressed

within B cells, making tisagenelecleucel a suitable target of DLBCL. It uses 4-1BB co stimulatory

domain with a single chain variable fragment (scvf) capable of recognising CD19 in its native form.

The scvf is obtained from FMC63 which is a monoclonal antibody from mouse ( Zavras et al.,

2019).

Structure of Tisagenelecleucel ( Zavras et al., 2019)

The use of cancer vaccines to modify the body’s immune responses by stimulating it to fight cancer is

also a current trend in cancer immunotherapy. It consists of preventive vaccines and therapeutic

vaccines. The preventive vaccines are based on antigens carried by infectious agents which the host’s

immune system recognises as foreign invaders followed by the stimulation of an immune response

which confers long term immunity (Speiser and Flats, 2014). The hepatitis B virus (HBV) vaccines

and human papilloma virus (HPV) vaccines are FDA-approved (Knutson and Mittendorf, 2015).

Within the immune system are a number of checkpoint pathways focusing on T-cell activation that

play a crucial part in modulating anti-tumour immunity (Sasidharan and Elkord, 2018). Immune

checkpoint inhibitors, a class of drugs aimed to increase immune response against cancer cells, binds

with the T-cell surface molecules such as CTLA-4, PD-1, T-cell immunoglobulin and mucin domain

containing protein 3 (Tim-3), to remove inhibition and enable cytotoxic T cells to attack cancer cells

for destruction (Kakimi et al., 2016). From 2011 to 2016, a number of checkpoint inhibitors became

FDA approved. Anti-CTLA-4 antibodies ipilimumab to treat metastatic melanoma was the first to be

approved in 2011, which marked the start of a new dimension of cancer immunotherapy. The anti-PD-

1 antibodies pembrolizumab and nivolumab were approved for metastatic melanoma in 2014,

Nivolumab in 2015 for previously treated advanced or metastatic squamous lung cancer and small cell

lung cancer, and in 2016, anti-PD-L1 atezolizumab was approved for bladder cancer and nivolumab

were approved for Hodgkin lymphoma (Barbee et al., 2015; Hatae and Chamoto, 2016; Swart et al.,

2016; Kates et al., 2016; Marrone and Brahmer, 2016).

SUCCESSES AND FAILURES OF IMMUNOTHERAPHY

So many successes have been attributed to immunotherapy in variety of cancers including Non- small

cell lung cancer (NCSLS), and metastatic melanoma.

SUCCESS RECORDED IN NCSLS

A case study report by Hamid in 2014, A 60-year-old man with a smoking history presented at the

clinic with a lung mass. Biopsy showed area of necrosis and malignant cells. Chemotherapy was

administered (Cosplastin and Pemetrexed in this case) which was accompanied by response such as

tumor shrinkage that allowed for surgical resection but after 6 months there was relapse as

computated tomography (CT) scan reveals new lesions in the left lung.

In 2013, He enrolled for immunotherapy trial with check point inhibitor. Nine weeks after the

commencement of the trial, it was reported to be stable and subsequent scans revealed tumour

shrinkage.

Subsequently in 2008, a 66-year-old man with a mass on the neck (Left side) presents at the clinic and

went through parotidectomy with evidence of malignancy found. He was treated with chemotherapy

(Carboplatin, docetaxel) and radiation which was completed 2009 and went into remission until 2011

when lung and lytic iliac lesions was observed. In 2013, patient enrolled for immunotherapy clinical

trial and six weeks after the initiation of the trial, he became stable and there was huge reduction in

the size of his tumour (Pulmonary nodules) (Hamid, 2014).

SUCCESS IN METASTATIC MELANOMA

Immunotherapy was found to improve survival of patients with metastatic melanoma in a phase III

study conducted by Hodi et al and published in the New England Journal of Medicine (NEJM). In the

study, 676 patients positive for HLA- A*0201 with stage III or IV melanoma that had not been

excised surgically were recruited. Out of the participants, some groups were treated with Ipilimumab,

another with Ipilimumab and glycoprotein (gp) 100 peptide vaccine, and another with gp100 alone.

They concluded that the immunotherapy agent Ipilimumab is effective and improves patients survival

with or without the gp100.

In August 2015, it was announced that Jimmy Carter had overcome metastatic melanoma three

months after the administration of pembrolizumab, his tumour is now in remission (Cancer Research

Institute, 2020).

FAILURES

Successes recorded in the past since the inception of immunotherapy has been huge but not without its

corresponding challenges and failures. A few of these include; Inability to pre-determine effectiveness

of immunotherapy and patient’s overall response - Inability to identify tumor specific biomarker -

variations and heterogeneity of the different cancer types, and the cost implications of immunotherapy

agents (Adams, 2015, Chiriva-Internati and Bot, 2015, Tartari et al, 2015 Zugazagoitia, 2016).

Immunotherapy (immune-oncology) has been a major approach that shifted cancer treatment

paradigm as many solid tumors are found to be immunogenic (Schreiber et al. 2011).

Immunotherapies rely on the activation of the immune system and they can therrefore have a delayed

antitumor activities (Hoos et al. 2010). Non-self, tumor-associated antigens generated during

malignant transformation can be recognized by the immune system, leading to tumour

antigen−specific T-cell responses and consequent cancer cell elimination (Galon et al. 2013;

Schreiber et al. 2011; Tartour and Zitvogel 2013). Immunotherapy involving the use of monoclonal

antibodies against checkpoint molecules, including programmed death (PD)-1, PD ligand (PD-L)1,

and cytotoxic T lymphocyte-associated antigen (CTLA)-4, is an effective approach which has yielded

clinical benefits in several tumor types (Pardoll 2012; Topalian et al. 2015). However, downside and

complications associated with this approach includes inability to accurately predict treatment

outcome, propensity for resistant, efficacy , individual patient response, and side effects (immune-

related adverse events) (Chiriva-Internati and Bot 2015; Pauken et al. 2019; Ventola 2017).

Identifying significant markers such as the availability of known targetable tumour-specific antigens

is a great limitation in immune-oncology. Similarly, targeting tumour-associated antigens, which are

also expressed by normal tissues, may cause off-target toxicities (Alatrash et al. 2013). Till date only

few predictive biomarkers for immunotherapy have been elucidated. PD-L1 and other check point

molecules have proved to be inconsistent and may vary in different tumours. The need to identify

predictive biomarkers that are more efficient has been a challenge because clinically predictive

genomic mutations in cancer differ with respect to their distributions across many cancer types

(Zugazagoitia et al. 2016).  Therefore, the identification of these mutations requires highly sensitive,

and comprehensive genetic sequencing technology, even for routine clinical care (Yuan et al. 2016;

Zugazagoitia et al. 2016).

One major factor contributing to failure of immunotherapy is the development of drug resistance,

which is believed to be caused by sub clonal cancer cell populations and branched clonal evolution

amongst others (Zugazagoitia et al. 2016). Mechanisms involved in drug resistance may be through

secondary genomic mutations in the drug, activation of alternative signalling pathways or reactivation

of a cancer pathway (Camidge et al. 2014; Zugazagoitia et al. 2016). Several patients with advanced

melanoma who had developed acquired treatment resistance to the pembrolizumab were assessed in a

study and factors that might have induced resistance were investigated using tumour biopsies obtained

from participants before treatment and after relapse, comparison was made in a bid to detect

mutations that evolved after imitating treatment (Zaretsky et al. 2016). Mutation in the JAK1/2 gene

interfering with the IFN-gamma signalling pathway leading to reduced gene expression in T cell

recognition and destruction of cancer was observed in two patients with observation of B2M gene

mutation in the third patients (Zaretsky et al. 2016).

Drugs targeting an immune checkpoint inhibitor for cancer therapy such as FDA approved

ipilimumab, nivolumab, pembrolizumab, atezolizumab and durvalumab are found to induce immune-

related adverse events (irAEs) have presented a major obstacle for the safe use of these therapies.

These irAEs have different types related to the target immune checkpoint inhibitor (Haanen et al.

2018). For example, hypophysitis is a common endocrine irAE observed following CTLA-4 blockade

in cancer patients, but rarely seen following PD-1 pathway blockade, in which thyroiditis is more

comon in the patients (Boutros et al. 2016; Eggermont et al. 2016; Robert et al. 2015). Combination

therapies involving these inhibitors are also found to cause irAEs, for instance, the use of nivolumab

and ipilimumab patients with melanoma caused high rate of severe irAEs (Shoushtari et al. 2018).

IrAEs may be caused by activation of immune responses unrelated to those targeting the tumor.

Alternatively, on target/off tumor responses may occur. However, the types of irAEs that occur

following checkpoint blockade do not appear to be specific to the type of cancer which suggests that

the cause of irAEs is a drug-induced loss of immune tolerance unrelated to the tumor (Boutros et al.

2016; Postow et al. 2018). The mechanism of irAEs may be explained by (i) initiating a new

autoimmune or inflammatory condition, (ii) exacerbation of a pre-existing autoimmune condition in

the patient (patients with pre-existing autoimmune diseases have largely been excluded from cancer

immunotherapy trials to date), (iii) tissue injury due to antitumor responses and (iv) aberrant reactions

to the checkpoint inhibitor itself (Haanen et al. 2018; Pauken et al. 2019).

Therefore, The need to manage irAEs has complicated the use of cancer immunotherapies and

subsequent, cancer treatment. Recently, high-dose corticosteroids effective in mitigating the

symptoms are used as first line for managing irAE, although this approach may be detrimental to the

development of host immune responses (Hu et al. 2003).

CANCER IMMUNOTHERAPY CLINICAL TRIALS

Clinical trial isa type of research that is based on studying and evaluationof outcomes of new

interventions and treatments on human subjects (WHO, 2018).

Current clinical trials in Immunotherapy listed on 'clinicaltrials.gov' include the use of tumour

infiltrating lymphocytes (TIL) in treating ovarian, urothelial, breast, and digestive tract cancer to see if

it could shrink tumour and as well safe to use. In this Phase II trial sponsored by the National Cancer

institute, patients white blood cell (WBC) were harvested from the tumour and grown into TIL

products which was later administered alongside Aldesleukin and followed up. This trial is estimated

to be completed by December 2024.

In another phase II trial sponsored by the Newlink Genetics corporation, patients with stage IV

melanoma were treated with ipilimumab, and Nivolumab (Check point inhibitors alone or in

combination with an experimental drug Dorgenmeltucel which is made up of irradiated allogeneic

melanoma cell lines HAM - 1, HAM 2 and HAM-3 to access safety of the drug and efficacy. This trial

is estimated to be completed by May 2033.

Conclusion

Cancer has been established to be a multigenic disease with high rate of mortality globally. It has

multiple aetiology ranging from genetics, environmental factors, smoking, and drug use. The immune

system has been bypassed by several mechanisms in various cancers and it has been worked on as a

potential source of treatment through immunotherapy. Further research is therefore necessary to

develop more treatment that would prevent and limit genetic predisposition, cure and overall contain

cancer globally.

Conflict of interest

All authors declared that there are no conflicts of interest.

© The Authors (s) 2021.

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