Chapter 1Microfilamentos Mitocondria

Lisosoma

Peroxisoma

Centriolos .

MicrotObulos

Aparato de Golgi

Reticula endoplasmatica

gruesa

NudeoPoros nudeares

Membrana ■ de plasma ,

NudeoloEnvoltura ^ nudear

Cromatin

Retjcwia . endoplasmatica fina Pibosomas

Introduction

1.1 C A N C ER

( .'a iiG e r is the disease state in w hich normal grow th controtHng m echanism s are

permanently im paired, perm itting the progressive grow th o f celis w ithout reaching

grow th e(|uiiibrium. These cells show imliniited replication potential, abtionnal

differentiation and improved survival. About 85% o f all the cancers are solid tumors,

l l i is abnormal behavior arises out o f the activation o f certain specialized genes called

protooncogenes to Oncogenes in the presence o f physical, chemical and viral

carcinogens.' Once group of such ceils are activated, these divide unlimitedly, causing

the neighbouring normal ceils to strive. There are over 200 different known cancers that

afflict liumans, Various changes that a cancer cell shows are as described.

Cfiaptiir 1 ___________________________________________ Introductwn

1.2 M O R PH O .LO G IC A L CH A N G ES IN A C A N C E R C E L L

CyloskeJeUd changes- The distribution and activity o f the microfilaments and

inicrotubules change, These alterations change the ways in which the cell interacts with

neigliboring cells and aiter the appearance of the ceils.

Cell adkskm/motiiity- The reduction o f cell:cell and celhexiracelliilar matrix adhesion

allows large masses o f cells to form. Cancer cells do not exhibit contact inhibition and are

able to continue to grow even when surrounded by other cells. The alterations in cell

adhesion also impact on the ability o f the cells to move. Cancer cells must be able to

move and migrate in order to spread, and cell adhesion plays a m ajor role in regulating

ceil movement.

Nuclear changes- The shape and organization o f the nuclei o f cancer cells markedly

differ from that o f the nuclei o f normal cells o f the same origin. This change in

appearance may be useful in the diagnosis and staging o f tumors.

Enzyme production- Cancer cells often secrete enzymes that enable them to invade

neighboring tissues. These enzymes digest away the barriers to migration and spread o f

the tumor cells.

CHapterl____________________________________________________ Introduction

I

(4fK trout ph«natyp»

Fig. 1 M orphological changes in a cancer ceil

chapter 1 Introduction

1.3 PA TH O G EN ESIS O F C A N C ER

MUagensCardnogene

VruseshradiaitionGenetic

precfspoelion

Es»rtialcellular

functionsRoto

TransformingOncogene

The dual nature of oncogenes

'spontaneous' neoplasm •

Fig. 2 Pathogenesis of cancer

Cancer is fundamentally a disease o f breakdown o f regulation o f tissue growth. In order

for a normal cell to transform into a cancer cell, the genes which regulate cell growth and

differentiation must be altered.^

The affected genes are divided into two broad categories. O ncogenes are genes which

promote cell growth and reproduction. T u m o r su p p resso r genes are genes which inhibit

cell division and survival. Cancer can occur through the arrangement o f novel oncogenes,

the inappropriate and over-expression o f normal oncogenes, or by the under-expression

or disabling o f tum or suppressor genes. Specifically, changes in multiple genes are

required to transform a normal cell into a cancer cell.^ Genetic changes occur at different

levels and by different mechanisms. The gain or loss o f an entire chromosome can occur

through errors in mitosis. M ore common are mutations, which are changes in

■',/ Introdactuni

(he nucleotide sequence o f genomic DN A, These mutations caii be large scale oi' small

scale. L arge scale iiisitatioiis involve the deletion or gain o f a portion o f a chroniosonie.

These occur by genomic amplifications and translocation, Genom ic am plification occurs

when a cell gains many copies (often 20 or more) o f a small chroraosomal locus, usually

containing one or more oncogenes and adjacent genetic material. Translocation occui's

when two separate chromosomal regions become abnorm ally fused, often at a

characteristic location, S iia ii-scale iiM tations include point mutations, deletions, and

insertions, which may occur in the promoter region o f a gene and atTect its expression, or

may occur in the gene's coding sequence and after the function or stability o f

its protein product. Disruption o:f a single gene may also re.5uft from integration o f

genomic material from a DNA virus or retrovirus, and resulting in the expression o f virai

oncogenes in the affected cell and its descendants.

Replication o f the massive data contained within the DNA o f living cells,

probabilistically result in some errors (mutations), Complex error correction and

prevention is an in-built process, and safeguards the cell against cancer, If significfint

error occurs, the da,maged cell can "self-destmct" through program m ed cell death,

termed apoptosis. i f the error control processes fail, then the m utations will survive and

be passed along to daughter cells.

I l ie errors which cause cancer are self amplifying compounding, for example:

A mutation in, the error-correcting machinery o f a cell m ight cause that cell and its

children to accumulate errors more rapidly.

* A further' niiitatiori in an oncogene miglit cause the cell to reproduce iiioi'e I’apidly

and more trequeiitly than its normal counterparts,

A iiirther mutation may cause loss o f a tum our siippressoi’ gene, disru|)ting tlie

apoptosis signalling pathway and resulting in the cell becom ing immortal.

A further mutation in signaling inachinery o f the cell might send error-caiising

signals to nearby cells.

The transformation o f normal cell into cancer is akin to a chain reaction caused by initial

errors, which compound into more severe errors, each progressively allowing tiie cell to

escape the controls that limit iioima! tissue growth. This rebellion-like scenario becomes

an undesirable survival o f the fittest, where the driving forces o f evolution work against

the body's design and enforcement o f order. Once cancer has begun to develop, this

ongoing process, termed ckmai evolution drives progression tow ards more invasive

stages;'

1.4 jV ffiCIIA N ISil O F M ETA STA SIS

1.4=1 F oniia tio ii of the firin ia iy fiin ior

Tumor ceils invade stroma and comm unicate w ith stromal cells. Tum or is avascular.

Both tumor and host cells promote metastasis by activating growth factor pathways,

permiting invasion, and endorsing angiogenesis. Host cells inhibit metastasis by putting

up tissue barriers, activating immune cells to kill tumor, and inhibiting angiogenesis.

(fia y te r l _________________________________________ ________ Introduction

Cfidpter 1 ________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Intfodiution

1.4.2 Progressive growtli anci siiigiogenesis

Aiigiogenesis occurs when tumors secrete angiogenic agents such as VEGF and FGF, and

by their recriiiting lymphocytes and macropha.ges to secrete these agents as well, The

capillary basal membrane degrades locally, creating a vascular deform ity and allowing

new endothelial modeling. The tum or or macrophages may also secrete anti-aiigiogeriic

agents such as aiigiostatiri, endostatin, and thrornbospondin.

1.4.3 Isivasiosi

Tumor cells invade host stroma using enzymes, then enter biood stream or lymphatics

(which have thinner walls). The host reaction to this invasion is a fibrous extra cellular

membrane called the “desmoplastic response.”

1.4.4 T ransport' of cancer cells

Single cells or aggregates detach. B lood stream is very intim idating to cancer cells, so

aggregates survive better, and become trapped in micro vasculature downstream, These

aggregates adhere to endothelial cells or even the basal membrane and invade distant

tissue. Interestingly, presence o f cancer cells in circulating blood and bone m arrow is not

associated with worse clinical outcome. Cancer cells deposit based on circulation

meclianics and chemokines in target tissue, GI cancers go to liver, breast cancers to

lungs, Cancer then has to set up new microenvironment - this is an ineiftcient step.

Growth factors supporting new cancer include TGF-p and IGF 1.Tum or ceils express

chemokine receptors complementary to target organ chemokines. Therefore, chemokines

iniTuence patterns o f spread between organs.

1.4.5 D o r i iM c y

One model for relapse is that dormancy has persisteiit tiny pre-angiogenic metastases, in

which tumor cell growth is balanced by apoptosis.

Cfuipter 1_________ __________________________ _____________________ Introduction

1.5 C A N C ER IN C ID EN C E W O R L D W ID E

Cancer is tlie leading cause o f death worldwide, as per WHO worldw ide statistics 7.8

million died o f cancer in 2008. A total o f 1,638,910 new cancer cases and 577,190 deatlis

from cancer are projected to occur in the United States this year i.e. 2012.'* Based on the

projections, cancer deaths will continue to rise with an estimated 9.0 million people dying

from cancer in year 2015 and Deaths from cancer worldwide are projected to continue

rising, with an estimated 13, i million deaths in 2030,

Cfumter l Introdw m n

Source: Estimated new cases are tesed on 1996-200B incidence rates from 47 states and the Districl of Columbia as repofled bs/ the Noriii

oil US iWoilality Data, 1994 to 2008, National Center for Health Statistics, Centers for Disease Conlrot and Preveritioti.

Cancer Farts & Figures- 2012

Fig. 3 Cancer tocideiice Worldwide

As we can see from the statistics (figure 3) above that major deaths per year are occiu'ring

due to cancer and unfortiuiately we still have limited number treatnietits available,

Treatments available also have great deal o f patient incompliance. This draws the great

attention of researchers to develop treatments for this deadly disease, Conventional

nietliods available for the treatment include surgical removal o f the tumor followed by

I'adiotherapy and chemotherapy to kill the residual cells and prevent the relapse. The

effectiveness o f cancer therapy in solid tumors depends on adequate delivery o f the

therapeutic agent to tumor cells, Inadequate delivery would result in residual tumor cells,

which in turn would lead to re growth o f tumors and possibly development o f resistant

cells.

1.6 IM PACT O F CANCER IN INDIA

The myth that cancer affects people mostly in the developed countries is being broken by

the fact that, o f the 10 million new cancer cases seen each year worldwide, nearly 5,5

million are in the less developed countries. Cancer is the second inost coniraon cause of

death in the developed world and a similar trend has emerged in the developing countries

too.

Cancer trequency in India is projected to be around 2,5 million, with over 8,00,000 new

cases and 5,50,000 deaths occurring each year due to this disease. More than 70% of the

cases report for diagnostic and treatment services in the advanced stages o f the disease,

which has lead to a poor survival and high mortality rate/^ The impact of cancer is fer

gi'eater than mere numbers. Its diagnosis causes immense emotional trauma and its

treatment, a major economical burden, especially in a developing country like India. The

initial diagnosis o f cancer is perceived by many patients as a grave event, with more than

Cfiayter 1_________________ ______________________________ IntroduUiov-

one-third o f them siilfering from anxiety and depression. Cancer is equally distressing for

the family as well. It could greatly affect both the fam ily’s daily functioning and

economic situation. The econom ic shock often includes both the loss o f incom e and the

increase o f expenses because o f the treatm ent and health care. This disease is associated

witl} a lot o f fear and despair in the country,

L6.1 D istribiition ®f V arious types C ancers across the Sulicontiiieiit

Among men, lung, esophagus, stomach, oral and pharyn.geal cancers are m ore prevalent,

while in women, cancers o f cervix and breast are m ost com m on, follow ed by those o f

stomach and esophagus-

Cfiapter 1 ______________ _____________ _______________ _____Introduction

l ,k2 D ifferent cancers occur in d ifferen t sta tes o f o iir country . 12 -14

e E.sophageal cancers: Southern states o f India like K arnataka and Tam il Nadu and

also in M aharashtra and Gujarat,

9 Stomach cancers; Southern India ivith the highest incidence in Chennai,

e Oral cancers: Kerala (South India)

e Phaiyngeal cancers: M umbai (W esteni India)

® Thyroid cancers among women: K erala

® Gall bladder cancer: N orthern India, particularly in Delhi and W est Bengal.

I /k 3 T rends in liicideiice of C an ce r m In d ia

A trend analysis o f the data on cancer incidence for the period 1964-96 has dem onstrated

that the overall occurrence o f cancer is increasing w ith am ong females, The greatest

increase among females was for cancer o f the breast and am ong males for cancer o f the

1 n

prosfate. Tliere was an increasing trend for lympliorna, urinary bladder, gall bladder and

brain tumors in both sexes. Cancer o f the colon was increasing in females and that o f the

kidney in males, Esophageal and stomach cancers were decreasing in both sexes.

Cervical cancer showed a decreasing trend. '

17 THERA„PIIJT1C STR A TEG IES F O R TUF. T R E A T M E N T O F C A N C E R

Cancer control strategies include early detection, treatment and palliative care.

Present cancer therapy should be based on the philosophy, "''even a siiigle cancer veil

should not remain mitreated in the body cmd nothing ks.s than complete elimimition of

tumor from an iiidividimi can he accepted’'.

Some approaches for the cancer therapy include:

1 . Chemotherapy: Inhibit the growth o f tum or cells by cytotoxic bioactives,

2 . Antiangiogenesis therapy: Inhibit the formation o f the blood vessels that supply the

tumor. .

3. ['lormonal therapy; Inhibit the gi'owth o f hormones, thereby preventing ])roriferaticm

o f prostatic and breast cancer.

4. Antimetastatic therapy; .Inhibit or prevent the invasive growth and metastatic spread.

5. Immunostimiiiant therapy: Reinfoi'ce the functions o f the immune system.

Except for a few cancer types (e.g. breast cancer), for which hormonal therapy or

immunotherapy is used, cytotoxic drugs remain the major form o f chemotherapy for

c a n c e r.C y to to x ic dmgs are a diverse class o f compounds that treat cancer primarily by

being toxic to cells that are rapidly growing and dividing, Despite the long history o f their

use, and the development o f numerous, new multiple dnig regimens for improved clinical

success, treatment failure is still frequently encountered

C l h y t e r l ___________ hitroductioti

(fiap terl _____________ ______________ __________________________ hitroductton

1.7,1 Cftiivenlioiiai d rug delivery metliods and their liniitotioiis

In chemotherapy, pharmacologically active cancer drugs reach the tum or tissue with poor

specificity and dose limiting toxicity. Conventional drug delivery niethods include oral.

and i.v. routes, There are several disadvantages to these methods; for example, ora!

administration o f tablets or capsules could result in disorderly pharm acokinetics due to

the exposure o f these agents to the metabolic pathways of the body. This can result in

larger than necessary doses being administered, which can fijrther cause increased

toxicity. Another route includes i.v. route. Following a system ic administration, drug

delivery to cells in solid tumors involves three processes, i.e., transport within a vessel

(e,g,, blood circulation), transport across vasculature walls into siiiT o im d in g tissues, and

finally to tum or cells. The traditional i.v. routes are often even m ore problematic. The

specificity o f some conventional i.v. drugs is low, resulting in harmful effects to healthy

tissues, Thus, to deliver therapeutic agents to tum or cells in vivo, one must overcome the

following problems:

> Drug resistance at the tumor level due to physiological barriers (non cellular

based mechanisms),

y Drug resistance at the cellular level (cellular meclianisms),

> Distribution, biotransformation and clearance of anticancer drugs in, the body.

Transport o f an anticancer drug in interstitiiim will be governed by physiological (i.e.

pressure) and physiochemical (i.e. composition, structure and charge) properties o f the

interstitium and by the physicochemical properties o f molecules (size, configuration,

charge and hydrophobicity) itself. Therefore the designing o f the d e l i v e r y system should

be in a manner to eventually overcome the aforementioned problems.

a. Systemic toxicity

Chemotherapy clutches a towering risk, and number o f times it lias been noticed that

more the drug is effective; more is the risk o f toxicity it carries. This is mainly due to

relatively narrow therapeutic window where the maximum tolerated dose is limited by

dose dependent toxicity. Depending on the choice of drugs, diifierent organs or tissues

can be affected by the non-specific action o f the cytotoxic a g e n t s , S o m e o f tiie

important side effects includes: Cardiotoxicity ,Hepatotoxicity, Nephrotoxicity,

Ototoxicity, Pain, Anemia, Depression o f the immune system, Hemorrhage, Secondary

neoplasms, Erythema, Nausea, Diarrhea o r constipation, Malnutrition, Hair loss, M em ory

loss, Dehydration, Vertigo, liem atonia, Dry mouth/ xerostomia, W eight loss o r gain.

W ater retetition and Sexual impotence.

t). Lack of ta rge t specifieity

Conventionally administered cytotoxic agents often extensively and indiscrirairiately bind

tissues and serum protein in a highly unpredictable manner. M any current therapies are

administered into the bloodstream and rely on the leaky vasculature o f tum or tissue to

accumulate the drug within the cancer. Only a small fraction o f the drugs reach the tum or

site, which in turn leads to reduced therapeutic efficacy and increased systemic drug

, ■ 20 toxicity.

c. Drug Resistance

Drug resistance is the foremost cause o f the treatm ent failure in cancer, This is tne core

problem being faced by the broad class o f the hydrophobic cytotoxic drugs. M echanism s

chapter 1_________ __________________________________________ Introduction

behind it mainly involves family o f energy dependent Iransporters that causes increased

etflux o f these hydrophobic moieties. These energy dependent transporters are known as

ATP-bitiding cassettes o r shortly ABC transporters. Proteins falling under this family

includes p-glyco proteins also known as ABCBI or MDR 1. There is intensive research

going on Ibr improvement in the treatment o f cancer to that includes new chemical entity

development and the development of novel ways to deliver existing drugs leading to

improved therapeutic index and reduced side effect. Improved delivery is made possible

by encapsulating the drug in novel drug delivery systems such as, liposomes,

rwHiopaiticles, micelles, microspheres and micro emulsions.

C fiap terl___________ ___________________________ _________Introduction

d. Poor Drug Selubilit]''

Most arrticancer drugs, especially those with excellent anticaiicer effects such as taxanes

(paclitaxel and docetaxel), camptothecins (topotecan and 9-amiiiocaraptothecjn),

topoisomerase II inhibitors (etoposide and teniposide) the aiitliracylines (doxorubicin,

epirubicin and daunorubicin), all Vinca alkaloids (vincristine, vinblastine, vinorelbine),

ifostamide and mitoxantrone have low bioavailability due to limited aqueous solubility.

Adjuvants such as emulsifiers like cremophore .EL for paclitaxel have to be used for the

clinical administration o f these drugs, which themselves are associated with serious side

effects, some o f which are life threatening.

ICeeping in mind these shortcomings o f the available therapeutic strategies, aims and

objectives o f the contemporary research were set and achieved, that would be discussed

in the chapters impending in line.

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Cfiapter 1 ____________ ________________________________________Jntroifuction

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(flew ter 1 ________________ ________ Introduction

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C l i a p t e r l __________________ __________ ________ _________ Introduction

17