Swapna Joshi

Pancreatic stellate cells: partners in crime with pancreatic cancer cells.

Pancreatic stellate cells (PSC) produce the stromal reaction in pancreatic cancer, but their role in cancer progression is not fully elucidated. We examined the influence of PSCs on pancreatic cancer growth using (a) an orthotopic model of pancreatic cancer and (b) cultured human PSCs (hPSC) and human pancreatic cancer cell lines MiaPaCa-2 and Panc-1. Athymic mice received an intrapancreatic injection of saline, hPSCs, MiaPaCa-2 cells, or hPSCs + MiaPaCa-2. After 7 weeks, tumor size, metastases, and tumor histology were assessed. In vitro studies assessed the effect of cancer cell secretions on PSC migration and the effect of hPSC secretions on cancer cell proliferation, apoptosis, and migration. Possible mediators of the effects of hPSC secretions on cancer cell proliferation were examined using neutralizing antibodies. Compared with mice receiving MiaPaCa-2 cells alone, mice injected with hPSCs + MiaPaCa-2 exhibited (a) increased tumor size and regional and distant metastasis, (b) fibrotic bands (desmoplasia) containing activated PSCs within tumors, and (c) increased tumor cell numbers. In vitro studies showed that, in the presence of pancreatic cancer cells, PSC migration was significantly increased. Furthermore, hPSC secretions induced the proliferation and migration, but inhibited the apoptosis, of MiaPaCa-2 and Panc-1 cells. The proliferative effect of hPSC secretions on pancreatic cancer cells was inhibited in the presence of neutralizing antibody to platelet-derived growth factor. Our studies indicate a significant interaction between pancreatic cancer cells and stromal cells (PSCs) and imply that pancreatic cancer cells recruit stromal cells to establish an environment that promotes cancer progression.

Sensitization of glioblastoma cells to irradiation by modulating the glucose metabolism

Because radiotherapy significantly increases median survival in patients with glioblastoma, the modulation of radiation resistance is of significant interest. High glycolytic states of tumor cells are known to correlate strongly with radioresistance; thus, the concept of metabolic targeting needs to be investigated in combination with radiotherapy. Metabolically, the elevated glycolysis in glioblastoma cells was observed postradiotherapy together with upregulated hypoxia-inducible factor (HIF)-1α and its target pyruvate dehydrogenase kinase 1 (PDK1). Dichloroacetate, a PDK inhibitor currently being used to treat lactic acidosis, can modify tumor metabolism by activating mitochondrial activity to force glycolytic tumor cells into oxidative phosphorylation. Dichloroacetate alone demonstrated modest antitumor effects in both in vitro and in vivo models of glioblastoma and has the ability to reverse the radiotherapy-induced glycolytic shift when given in combination. In vitro, an enhanced inhibition of clonogenicity of a panel of glioblastoma cells was observed when dichloroacetate was combined with radiotherapy. Further mechanistic investigation revealed that dichloroacetate sensitized glioblastoma cells to radiotherapy by inducing the cell-cycle arrest at the G2–M phase, reducing mitochondrial reserve capacity, and increasing the oxidative stress as well as DNA damage in glioblastoma cells together with radiotherapy. In vivo, the combinatorial treatment of dichloroacetate and radiotherapy improved the survival of orthotopic glioblastoma-bearing mice. In conclusion, this study provides the proof of concept that dichloroacetate can effectively sensitize glioblastoma cells to radiotherapy by modulating the metabolic state of tumor cells. These findings warrant further evaluation of the combination of dichloroacetate and radiotherapy in clinical trials. Mol Cancer Ther; 14(8); 1794–804. ©2015 AACR.

Molecular Chemotherapy and Chemotherapy: A New Front against Late-Stage Hormone-Refractory Prostate Cancer

Purpose: Stemming from its inherent heterogeneity, single-agent treatments are essentially ineffective against castration-resistant prostate cancer (CRPC). Thus, clinically relevant regimens that harness different modalities to maximize treatment efficacy without increasing cumulative toxicities are urgently needed. Based on this rationale, we investigated whether a novel combination of purine nucleoside phosphorylase–mediated, gene-directed enzyme-prodrug therapy (PNP-GDEPT) with docetaxel against CRPC has superior efficacy in comparison with individual treatments. Methods: The in vitro cell growth inhibition in differentially treated murine and human CRPC cell lines was established using a cell-viability assay. The extent of synergy, additivity, or antagonism between treatments was evaluated using CalcuSyn statistical analyses. The local and systemic effects of docetaxel and/or PNP-GDEPT were tested in both immunodeficient and immunocompetent mice against human and murine CRPC tumors, respectively. Subsequently, immunohistochemical analyses and an evaluation of serum cytokine and serum toxicity profiles were conducted to characterize the differential host responses to treatment. Results: The combined use of PNP-GDEPT and docetaxel led to strong synergistic cell killing in vitro. Compared with the individual modalities, a combination of the 2 led to a marked reduction in “local and distant” tumor growth in vivo, and importantly, with lowered doses and without additional toxicities. Immunomodulation was indicated by enhanced immune cell infiltration and altered serum cytokine levels. Furthermore, a lowering of T-helper type 2 cytokines, MCP-1, interleukin (IL)-4, IL-6, and IL-10 marked lower tumor burden and enhanced treatment efficacy. Conclusion: PNP-GDEPT and docetaxel are a potent combination against CRPC in immunocompetent and immunodeficient settings; these outcomes have implications of translational potential for improved treatment and management of CRPC patients. Clin Cancer Res; 17(12); 4006–18. ©2011 AACR.

Employing pancreatic tumor γ-glutamyltransferase for therapeutic delivery

γ-Glutamyltransferase (γGT) is a cell surface enzyme that catalyzes hydrolysis of the bond linking the glutamate and cysteine residues of glutathione and glutathione-S-conjugates. We have observed that human pancreatic tumor cells and tumor-associated stellate cells express high levels of this enzyme when compared to normal pancreatic epithelial and stellate cells. Detection of the protein in tumor sections correlated with γGT activity on the surface of the cultured tumor and stellate cells. We tested whether the tumor γGT could be employed to deliver a therapeutic to the tumor endothelial cells. GSAO is a glutathione-S-conjugate of a trivalent arsenical that is activated to enter endothelial cells by γGT cleavage of the γ-glutamyl residue. The arsenical moiety triggers proliferation arrest and death of the endothelial cells by targeting the mitochondria. Human pancreatic tumor and stellate cell γGT activated GSAO in culture and γGT activity positively correlated with GSAO-mediated proliferation arrest and death of endothelial cells in Transwell and coculture systems. A soluble form of γGT is found in blood, and we measured the rate of activation of GSAO by this enzyme. We calculated that systemically administered GSAO would circulate through the pancreatic blood supply several times before appreciable activation by normal blood levels of γGT. In support of this finding, tumor γGT activity positively correlated with GSAO-mediated inhibition of pancreatic tumor angiogenesis and tumor growth in mice. Our findings indicate that pancreatic tumor γGT can be used to deliver a therapeutic to the tumor.

Combination of palbociclib and radiotherapy for glioblastoma

The cyclin-dependent kinase inhibitor, palbociclib has shown compelling efficacy in breast cancer patients. Several pre-clinical studies of glioblastoma (GBM) have also shown palbociclib to be efficacious. In this study, we investigated palbociclib in combination with radiation therapy (RT) for treating GBM. We tested palbociclib (with and without RT) on four patient-derived cell lines (PDCLs; RB1 retained; CDKN2A loss). We investigated the impact of therapy on the cell cycle and apoptosis using flow cytometry, in vitro. Balb/c nude mice were intracranially injected with the PDCL, GBM-L1 and treated orally with palbociclib (with and without RT). Overall survival was measured. Palbociclib treatment resulted in a significant increase in the percentage of cells in the G1 cell cycle phase. Apoptotic cell death, measured by Annexin V was induced. Palbociclib combined with RT acted synergistically with the significant impediment of colony formation. The oral treatment of mice with palbociclib did not show any significant survival advantage when compared to control mice, however when combined with RT, a survival advantage of 8 days was observed. Our results support the use of palbociclib as an adjuvant treatment to RT and warrant translation to the clinic.

Alterations in the mitochondrial responses to PENAO as a mechanism of resistance in ovarian cancer cells.

OBJECTIVE The purpose of this study was to test PENAO, a promising new organoarsenical that is in phase 1 testing in patients with solid tumours, on a range of ovarian cancer cell lines with different histotypes, and to understand the molecular basis of drug resistance exhibited by the endometrioid ovarian cancer cell line, SKOV-3. METHODS Proliferation arrest and cell death induced by PENAO in serous (OVCAR-3), endometrioid (SKOV-3, TOV112D), clear cell (TOV21G) and mucinous (EFO27) ovarian cancer cells in culture, and anti-tumour efficacy in a murine model of SKOV-3 and OVCAR-3 tumours, were measured. Cells were analysed for cell cycle arrest, cell death mechanisms, reactive oxygen species production, mitochondrial depolarisation, oxygen consumption and acid production. RESULTS PENAO demonstrated promising anti-proliferative activity on the most common (serous, endometrioid) as well as on rare (clear cell, mucinous) subtypes of ovarian cancer cell lines. No cross-resistance with platinum-based drugs was evident. Endometrioid SKOV-3 cells were, however, shown to be resistant to PENAO in vitro and in a xenograft mouse model. This resistance was due to an ability to cope with PENAO-induced oxidative stress, notably through heme oxygenase-1 induction, and a shift in metabolism towards glycolysis. The adaptive glycolytic shift in SKOV-3 was targeted using a mTORC1 inhibitor in combination with PENAO. This strategy was successful with the two drugs acting synergistically to inhibit cell proliferation and to induce cell death via apoptosis and autophagy. CONCLUSION Mitochondria/mTOR dual-targeting therapy may constitute a new approach for the treatment of recurrent/resistant forms of epithelial ovarian cancer.

PANCREATIC STELLATE CELLS STIMULATE PANCREATIC CANCER GROWTH AND METASTASIS: FINDINGS OF A NOVEL ORTHOTOPIC MODEL OF PANCREATIC CANCER

AACR Centennial Conference: Translational Cancer Medicine-- Nov 4-8, 2007; Singapore B78 Pancreatic stellate cells (PSCs) produce the stromal reaction in pancreatic cancer (PC), but their role in cancer progression has not been fully elucidated. Aims: To assess the influence of PSCs on PC growth using i) an orthotopic model of pancreatic cancer and ii) in vitro studies with cultured human PSCs and MiaPaCa2 (a human PC cell line). Methods: I) In vivo model: Athymic mice received an intrapancreatic injection of one of the following - saline (S), human PSCs (P), MiaPaCa2 cells (M), or human PSCs + MiaPaCa2 (1:1; P+M). After 7 weeks, mice were killed and tumour size and metastasis assessed. Tumour histology was assessed with HE (b) MiaPaCa2 apoptosis - TUNEL staining to assess basal and H2O2-stimulated MiaPaCa2 cell apoptosis, in the presence and absence of PSC secretions. Results: I) Orthotopic model: Compared to mice injected with M alone, mice injected with P+M exhibited i) a significant increase in tumour size (20-fold larger tumour); ii) more frequent liver metastasis (50% P+M vs 10% M; p < 0.02); iii) significantly higher epithelial cell numbers; and iv) significantly increased numbers of activated PSCs in fibrotic bands. No tumours were found in mice injected with PSCs alone. II) In vitro studies: (a) MiaPaCa2 proliferation was increased upon exposure to PSC secretions [24h - 217.4±29.5*, 48h - 195.5±15.8*, 72h - 245.6±44.5* % of control; *p<0.005]. (b) MiaPaCa2 apoptosis - Both basal and H2O2 stimulated apoptosis was significantly inhibited by PSC secretions. [Data as fold change : basal apoptosis 1; PSC secretions 0.45±0.05*, H2O2 16.39±2.34**; H2O2+PSC secretions 3.59±0.81*; *p<0.01]. Conclusions: i) Pancreatic tumour growth and metastasis are significantly increased in mice receiving PSCs+MiaPaCa2 compared to those receiving MiaPaCa2 alone. The increase in tumour size is due to increased tumor cell number and not merely to fibrosis. ii) PSC secretions induce proliferation and inhibit apoptosis of PC cells. Implications: PSCs establish an environment that promotes tumour progression by stimulating proliferation and reducing apoptosis of pancreatic cancer cells.

Dual targeting of mitochondrial function and mTOR pathway as a therapeutic strategy for diffuse intrinsic pontine glioma

Diffuse Intrinsic Pontine Gliomas (DIPG) are the most devastating of all pediatric brain tumors. They mostly affect young children and, as there are no effective treatments, almost all patients with DIPG will die of their tumor within 12 months of diagnosis. A key feature of this devastating tumor is its intrinsic resistance to all clinically available therapies. It has been shown that glioma development is associated with metabolic reprogramming, redox state disruption and resistance to apoptotic pathways. The mitochondrion is an attractive target as a key organelle that facilitates these critical processes. PENAO is a novel anti-cancer compound that targets mitochondrial function by inhibiting adenine nucleotide translocase (ANT). Here we found that DIPG neurosphere cultures express high levels of ANT2 protein and are sensitive to the mitochondrial inhibitor PENAO through oxidative stress, while its apoptotic effects were found to be further enhanced upon co-treatment with mTOR inhibitor temsirolimus. This combination therapy was found to act through inhibition of PI3K/AKT/mTOR pathway, HSP90 and activation of AMPK. In vivo experiments employing an orthotopic model of DIPG showed a marginal anti-tumour effect likely due to poor penetration of the inhibitors into the brain. Further testing of this anti-DIPG strategy with compounds that penetrate the BBB is warranted.

Integration of genomics, high throughput drug screening, and personalized xenograft models as a novel precision medicine paradigm for high risk pediatric cancer

ABSTRACT Pediatric high grade gliomas (HGG) are primary brain malignancies that result in significant morbidity and mortality. One of the challenges in their treatment is inter- and intra-tumoral heterogeneity. Precision medicine approaches have the potential to enhance diagnostic, prognostic and/or therapeutic information. In this case study we describe the molecular characterization of a pediatric HGG and the use of an integrated approach based on genomic, in vitro and in vivo testing to identify actionable targets and treatment options. Molecular analysis based on WGS performed on initial and recurrent tumor biopsies revealed mutations in TP53, TSC1 and CIC genes, focal amplification of MYCN, and copy number gains in SMO and c-MET. Transcriptomic analysis identified increased expression of MYCN, and genes involved in sonic hedgehog signaling proteins (SHH, SMO, GLI1, GLI2) and receptor tyrosine kinase pathways (PLK, AURKA, c-MET). HTS revealed no cytotoxic efficacy of SHH pathway inhibitors while sensitivity was observed to the mTOR inhibitor temsirolimus, the ALK inhibitor ceritinib, and the PLK1 inhibitor BI2536. Based on the integrated approach, temsirolimus, ceritinib, BI2536 and standard therapy temozolomide were selected for further in vivo evaluation. Using the PDX animal model (median survival 28 days) we showed significant in vivo activity for mTOR inhibition by temsirolimus and BI2536 (median survival 109 and 115.5 days respectively) while ceritinib and temozolomide had only a moderate effect (43 and 75.5 days median survival respectively). This case study demonstrates that an integrated approach based on genomic, in vitro and in vivo drug efficacy testing in a PDX model may be useful to guide the management of high risk pediatric brain tumor in a clinically meaningful timeframe.

Abstract A12: Genomically unstable glioblastoma are sensitive to Parp inhibition

Background: The development of effective targeted drugs for the treatment of glioblastoma (GBM) represents a major unmet need. Veliparib (ABT-888; Abbvie) inhibits both PARP1 and PARP2 (poly[ADP-ribose] polymerase). The successful clinical application of veliparib and other PARP inhibitors (PARPi) will be assisted by the identification of predictive biomarkers. Materials and Methods: We performed whole genome sequencing (WGS) on ten GBM specimens with matched normal DNA. Mutations were detected using qSNP and GATK and indels called with Pindel and GATK. Somatic structural variants were identified using the qSV package. For all ten specimens we developed patient derived cell lines (PDCLs). We tested the efficacy of the combination of veliparib and temozolomide (TMZ) on all of the PDCLs. Results: Strikingly, in 2 patient samples denoted as G89 and G54, the mutation rate was at least 16-fold higher compared to the other 8 participants. G89 and G54 exhibited a large number of single nucleotide variants (SNVs), insertions, deletions and structural variant (SV) events (>2 million) when compared to the other 8 patient samples. The scale of genomic instability suggested defects in DNA maintenance, which could potentially define sensitivity to DNA damaging agents. Upon closer examination of the mutational profile of G89 and G54, mutations were found in at least one of the mismatch repair (MMR) genes: MLH1, MSH2, MSH6 and PMS2. We also detected mutations in other genes involved in DNA maintenance such as XRCC4, FANCA, FANCD2, ATR, RPA1, REV3L and PARP1. We designated these patients9 GBM as U-GBM class. We found the U-GBM class of tumors, G89 and G54 to be hypersensitive to the combination of TMZ/veliparib. Conclusion: Mutations in DNA maintenance pathways may be a method for selecting patients for therapies involving the combination of DNA damaging agents such as radiotherapy, and PARP inhibitors. Additionally, the signature associated with genomically unstable GBM may be a method of identifying potential responders to PARP inhibitor therapy. Citation Format: Kerrie L. McDonald, Mustafa Khasraw, Toni Rose Jue, Swapna Joshi, Julia Yin. Genomically unstable glioblastoma are sensitive to Parp inhibition. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr A12.