Supplementary Material

Co-Localized Delivery of Rapamycin and Paclitaxel to Tumors Enhances

Synergistic Targeting of the PI3K/Akt/mTOR Pathway

Elvin Blanco, Takafumi Sangai, Suhong Wu, Angela Hsiao, Guillermo U. Ruiz-Esparza, Carlos

A. Gonzalez-Delgado, Francisca E. Cara, Sergio Granados-Principal, Kurt W. Evans, Argun

Akcakanat, Ying Wang, Kim-Anh Do, Funda Meric-Bernstam, and Mauro Ferrari

Drug-containing, long-circulating polymer nanoparticles preferentially accumulate in

tumors through vascular fenestrations: mechanism of nanotherapeutics for drug synergy

Figure S1 schematically outlines the hypothesized mechanism of action behind

nanoparticle delivery of synergistic drugs to breast tumors. Long-circulating polymeric

nanoparticles navigate the blood stream, their small size permitting avoidance of the

reticulendothelial system (RES) and extravasation through fenestrations in tumor-associated

vasculature (EPR effect). Once in the tumor, drugs are released in a controlled fashion,

providing site-specific, synergistic tumor treatment.

Resulting rapamycin and paclitaxel nanoparticles were monodisperse and small in size

Figure S2 represents a transmission electron microscopy (TEM) micrograph of

rapamycin and paclitaxel nanoparticles, depicting their nanoscale size range (~9 nm), their

core-shell architecture, and their monodispersity.

Nanoparticle size and surface charge did not vary significantly depending on

formulation, and were stable for long periods of time in physiological media

Nanoparticles containing either rapamycin, paclitaxel, or a combination of both, were

fabricated and size and surface charge evaluated via dynamic light scattering and zeta potential

analysis. As can be seen in Figure S3, the nanoparticle size (~9 nm) and surface charge (-4

mV) did not vary significantly depending on nanoparticle formulation. Nanoparticle stability, as

determined via nanoparticle size measurements at predetermined timepoints, was maintained

over the course of 7 d. Atomic force microscopy examination of nanoparticles 7 d after

incubation in serum confirmed the preservation of nanoparticle morphology and stability for

prolonged time periods.

Rapamycin and paclitaxel in free and nanoparticle form demonstrated similar patterns of

growth inhibition in breast cancer cells in vitro

Sulforhodamine B assays were performed to determine growth inhibitory effects of free

drug and nanoparticle formulations in MDA-MB-468 and MCF-7 cells. Figure S4 demonstrates

that minimal difference in growth inhibition was observed between free drug preparations and

nanoparticle formulations after 4 d incubation with cells. Paclitaxel had a nominal impact on

growth inhibition at lower doses, proving highly efficacious only at higher doses in both free and

nanoparticle form. Rapamycin and combination nanoparticles proved more effective at

inhibiting breast cancer cell growth compared to paclitaxel at low doses. At higher doses,

rapamycin growth inhibition plateaued, and both paclitaxel and combination preparations

resulted in significant growth suppression.

Rapamycin and paclitaxel nanoparticles possessed long blood-circulation times,

preserved precise ratios of drugs within tumors, and accumulated more in tumors than in

organs of the RES

The biodistribution of rapamycin and paclitaxel, individually encapsulated within

nanoparticles and administered concomitantly at a ratio of 3:1 rapamycin:paclitaxel (15:5 mg/kg)

to mice bearing MDA-MB-468 tumors, was evaluated in different organs at timepoints of 24 and

48 h following intravenous administration (Figure S5). Rapamycin and paclitaxel were present

in plasma at timepoints of 24 and 48 h after administration. Both drugs were found to a greater

extent in tumors at both timepoints compared to liver and spleen. Importantly, the ratio of

rapamycin to paclitaxel was well preserved in tumors at the early timepoint of 24 h, but not at

the later timepoint of 48 h.

Nanoparticles containing both rapamycin and paclitaxel (R/P), in a 1:2 ratio, were

administered to mice bearing MDA-MB-468 tumors and drug levels determined (Figure S6).

Rapamycin nanoparticles and paclitaxel nanoparticles were mixed and administered as a

cocktail to mice as a point of comparison (R+P). Rapamyicin and paclitaxel were found present

in plasma at timepoints of 24 h after intravenous injection (Figure S6a). Precise ratios (1:2

rapamycin:paclitaxel) were preserved at timepoints of 24 h (Figure S6b). Rapamycin and

paclitaxel concentrations were compared to drug concentrations in liver and spleen (Figure

S3c). Rapamycin and paclitaxel was found in heightened amounts in tumors compared to liver

and spleen at 24 h.

Nanoparticles containing both rapamycin and paclitaxel effectively suppressed tumor

growth inhibition in vivo compared to free drug and individual nanoparticle combination

controls

The antitumor efficacy of different formulations of rapamycin and paclitaxel, including co-

administration of both individual nanoparticle formulations and free drug preparations, was

examined in mice bearing MDA-MB-468 tumors (Fig. S7). As can be seen in the figure, co-

administration of individual rapamycin and paclitaxel nanoparticles resulted in significant tumor

growth inhibition compared to controls. Growth inhibition was similar to free drug preparations

of rapamycin, delivered intraperitoneally, and paclitaxel, delivered intravenously. Both treatment

arms of the study were less effective at suppressing tumor growth compared to the nanoparticle

formulation consisting of co-encapsulated drugs at a specific ratio of 3:1 rapamycin:paclitaxel at

a dose of 15:5 mg/kg. Moreover, co-encapsulation of rapamycin and paclitaxel at a ratio of 3:1

but at a lower dose of 1.5:0.5 mg/kg rapamycin:paclitaxel proved as effective as nanoparticles

containing rapamycin alone at a dose of 1.5 mg/kg, with paclitaxel incorporation offering no

additional benefit with regards to tumor growth suppression compared to nanoparticles

delivered at the dose of 15:5 mg/kg rapamycin:paclitaxel.

In vitro synergistic growth inhibition profiles and combination indices predict efficacy

responses in vivo

Nanoparticles containing different ratios of rapamycin and paclitaxel that demonstrated

disparate degrees of synergy in vitro were administered in vivo and their antitumor efficacy

examined (Fig. S8). As demonstrated in Figure 2, nanoparticles containing a 3:1 ratio of

rapamycin to paclitaxel were more synergistic in MCF-7 breast cancer cells than nanoparticles

composed of a 1:2 ratio. These ratios (15:5 mg/kg and 5:10 mg/kg RAP:PTX) were

administered intravenously to mice bearing MCF-7 breast tumors (n = 10). As can be seen in

the Figure S4, tumors receiving a low dose of PTX (5 mg/kg) failed to have an impact on tumor

growth, demonstrating a growth pattern similar to tumors receiving vehicle controls (no drug).

As was seen in the MDA-MB-468 breast cancer cell line (Fig. 4), rapamycin had little effect on

tumors, resulting in tumor stabilization throughout the course of treatment rather than

regression. Tumors receiving a 3:1 ratio of RAP:PTX regressed from a starting volume of 126 ±

9 mm3 to 103 ± 12 mm3 by day 7. By comparison, tumors in mice receiving nanoparticles

containing a 1:2 ratio of RAP:PTX grew slightly to an average size of 159 ± 7 mm3 during the

same time frame. Tumors in mice receiving a 3:1 ratio of RAP:PTX continued to regress over

time, reaching a value of 94 ± 8 mm3 by day 14 and a volume at the end of the study of 80 ± 10

mm3 (day 24). While initially showing signs of growth, tumors in mice receiving nanoparticles

containing a 1:2 ratio of RAP:PTX eventually decreased to a final volume of 110 ± 11 mm3 by

the end of the study. These findings demonstrate that the 3:1 ratio of RAP:PTX was superior to

a 1:2 ratio at inhibiting tumor growth in vivo, a synergistic potential gleaned and predicted from

in vitro combination index analyses (Fig. 2).

Nanoparticle delivery of rapamycin and paclitaxel yields insights into mechanisms of

synergy

Tumors excised from mice receiving nanoparticles containing rapamycin and paclitaxel

were examined using reverse phase protein array (RPPA) analysis for relative protein

expression levels. Table S1-3 contains proteins detected via RPPA analysis of tumors

extracted from mice receiving paclitaxel nanoparticles alone (nPTX, 5 mg/kg), rapamycin

nanoparticles alone (nRAP, 15 mg/kg), and nanoparticles containing both rapamycin and

paclitaxel co-loaded inside (rapamycin:paclitaxel 15:5 mg/kg). Proteins outlined in blue

represent those of interest related to the PI3K/Akt/mTOR signaling pathway.

Figure S1. Rapamycin and paclitaxel nanoparticles deliver drugs specifically to tumors. Small size and poly(ethylene) glycol on the surface contribute towards RES evasion, while fenestrations in tumor vasculature permit accumulation within tumors.

Figure S2. TEM micrograph of rapamycin and paclitaxel nanoparticles imaged using 2% PTX counterstain. The scale bar represents 100 nm.

Figure S3. Nanoparticle size and surface charge did not vary significantly depending on formulation, and were stable for long periods of time in physiological media. (a) Histograms of nanoparticles of varying formulations including paclitaxel nanoparticles (nPTX), rapamycin nanoparticles (nRAP), and rapamycin/paclitaxel nanoparticles (nR/P, ratio 3:1), as determined by dynamic light scattering (DLS). (b) Histograms of surface charge of nanoparticles as determined by zeta potential analysis. (c) Stability over time of nanoparticles of different formulations in serum at 37ºC as determined via DLS. (d) Atomic force microscopy examination of nanoparticle size and morphology 7 d after incubation in serum at 37ºC.

Figure S4. Nanoparticles containing both rapamycin and paclitaxel synergistically inhibited breast cancer cell growth in a manner analogous to free drug combinations in vitro. (a) and (c) represent growth inhibition assays in MCF-7 and MDA-MB-468 breast cancer cells following administration of free PTX (PTX), free RAP (RAP) or a combination of drugs at a 3:1 ratio of RAP:PTX. (b) and (d) represent growth inhibition assays in MCF-7 and MDA-MB-468 cells treated with paclitaxel nanoparticles (nPTX), rapamycin nanoparticles (nRAP), and nanoparticles containing both rapamycin and paclitaxel (nR/P) at a 3:1 ratio of RAP:PTX.

Figure S5. Rapamycin and paclitaxel packaged individually in nanoparticles and co-administered to mice bearing MDA-MB-468 breast tumors had sustained presence in the blood, adequately accumulated in tumors, and maintained drug ratios at early timepoints. Rapamycin and paclitaxel were individually encapsulated within single nanoparticles, after which they were physically mixed and administered intravenously at a dose of 15:5 mg/kg (3:1 rapamycin:paclitaxel). Concentrations of rapamycin and paclitaxel were determined in plasma extracted from mice (a). (b) Concentration of drugs in liver and spleen of mice compared to drug concentrations in tumors. Results are shown as mean ± SE. Statistical analysis was performed after normalization using liver concentrations (**, p<0.01; ***, p<0.001 vs. tumor).

Figure S6. Nanoparticles containing both rapamycin and nanoparticles at a ratio of 1:2 rapamycin:paclitaxel showed sustained presence in plasma, precisely preserved the ratio in tumors, and accumulated to a larger extent in tumors than in organs comprising the reticuloendothelial system. Rapamycin and paclitaxel were either packaged within the same nanoparticle (nR/P, 1:2) or individually encapsulated within single nanoparticles, after which they were physically mixed together (nR+P) and administered to mice bearing MDA-MB-468 breast tumors. Concentrations of rapamycin and paclitaxel were determined in plasma (a) and tumor samples (b) extracted from mice 24 h after administration. (c) Concentration of drugs in liver (L) and spleen (S) of mice compared to drug concentrations in tumors (T). Results are shown as mean ± SE. Statistical analysis was performed after normalization using liver concentrations (**, p<0.01; ***, p<0.001 vs. tumor).

Figure S7. Nanoparticles containing both rapamycin and paclitaxel effectively suppressed tumor growth inhibition in vivo compared to free drug and individual nanoparticle combination controls. Tumor growth inhibition was examined following administration of free drug combinations (PTX CrEL and RAP DMSO), individual rapamycin and paclitaxel nanoparticles (nRAP, nPTX), and nanoparticles containing different ratios of both drugs (nR/P) to mice bearing MDA-MB-468 tumors (n=5). All doses were 15 mg/kg for rapamycin and 5 mg/kg for paclitaxel unless otherwise stated. Arrows denote administration timepoints. All treatments were administered intravenously with the exception of RAP DMSO, which was administered intraperitoneally. For clarity of presentation, symbols denoting statistical significance have been omitted. On day 14, groups nRAP, PTX CrEL+RAP DMSO, and nR/P 15:5 mg/kg showed significance compared to control (*, p<0.05). On Day 17, groups RAP DMSO, nRAP, nRAP+nPTX, and PTX CrEL+RAP DMSO showed significance of p<0.05 (*), while groups nR/P 1.5:0.5 mg/kg and nR/P 15:5 mg/kg showed significance of p<0.01 (**) compared to control. On day 21, PTX CrEL showed significance p<0.05 (*), nRAP showed significance of p<0.001 (***), and groups RAP DMSO, nRAP+nPTX, PTX CrEL+RAP DMSO, nR/P 1.5:0.5 mg/kg, and nR/P 15:5 mg/kg showed significance of p<0.0001 (****) compared to control. On day 24, PTX CrEL showed significance of p<0.05 (*), while groups RAP DMSO, nRAP, nRAP+nPTX, PTX CrEL+RAP DMSO, nR/P 1.5:0.5 mg/kg, and nR/P 15:5 mg/kg showed significance of p<0.0001 (****) compared to control.

Figure S8. Synergistic ratios obtained from combination index analyses predicted in vivo antitumor efficacy in murine models of breast cancer. Tumor growth inhibition following administration of individual rapamycin and paclitaxel nanoparticles (nRAP, nPTX) and nanoparticles containing different ratios of both drugs (nR/P) to mice bearing MCF-7 tumors (n=10). Arrows denote administration timepoints. Asterisks denote results that are statistically significant compared to the control group (*, p<0.05; **, p<0.01; ***, p<0.001; ****, p<0.0001).