Vaibhav Sahai

Clinical Benefits of Above-Standard Dose of Octreotide LAR in Patients With Neuroendocrine Tumors for Control of Carcinoid Syndrome Symptoms: A Multicenter Retrospective Chart Review Study

BACKGROUND Octreotide LAR is used in patients for control of carcinoid syndrome (CS) and other symptoms of hormone hypersecretion. The aim of this study was to examine reasons for octreotide LAR dose escalation and observe CS symptom improvement in patients with neuroendocrine tumors (NETs) who underwent octreotide LAR dose escalation at three cancer referral centers. METHODS Medical records for patients with diagnosis of carcinoid or pancreatic NET who had received one dose or more of octreotide LAR above 30 mg every 4 weeks from 2000 to 2012 were reviewed. Reasons for dose escalation and symptomatic outcomes were abstracted for each patient 3 months prior to and up to 12 months following the dose escalation. RESULTS Of the evaluated 239 NET patients, 53% were male, mean age at first dose escalation was 60 years (standard deviation [SD]: 11 years), and mean time from octreotide LAR initiation to first dose escalation was 1.7 years (SD: 2.0 years). The primary reasons reported for dose escalation were carcinoid or hormonal syndrome (62%) or radiographic progression (28%). The most common dose changes at the first dose escalation were 40 mg every 4 weeks (71%) and 60 mg every 4 weeks (18%). Of 90 patients in whom flushing was reported prior to first dose escalation, 73 (81%) were reported to have experienced improvement or resolution of their symptoms following the dose escalation. Of 107 patients who were reported to have experienced diarrhea before the first dose escalation, 85 (79%) were reported to have experienced improvement or resolution after first dose escalation. CONCLUSION The goal of improved symptom control is a common reason for dose escalation of octreotide LAR. This study suggests that escalation to above the standard dose of octreotide LAR of 30 mg every 4 weeks may result in improved CS symptom control.

BET Bromodomain Inhibitors Block Growth of Pancreatic Cancer Cells in Three-Dimensional Collagen

Pancreatic ductal adenocarcinoma (PDAC) is associated with pronounced fibrosis that contributes to chemoresistance, in part, through increased histone acetylation. Because bromodomain (BRD) and extra terminal domain (BET) proteins are “readers” of histone acetylation marks, we targeted BET proteins in PDAC cells grown in three-dimensional collagen. We show that treatment with BET inhibitors decreases growth of PDAC cells (AsPC1, CD18, and Panc1) in collagen. Transfection with siRNA against BRD4, which is increased in human PDAC tumors, also decreases growth of PDAC cells. BET inhibitors additionally decrease growth in collagen of PDAC cells that have undergone epithelial-to-mesenchymal transition or have become resistant to chemotherapy. Although BET inhibitors and BRD4 siRNA repress c-MYC only in AsPC1 and CD18 cells, downregulating c-MYC decreases growth of all three PDAC cell lines in collagen. FOSL1, which is also targeted by BET inhibitors and BRD4 siRNA in AsPC1, CD18, and Panc1 cells, additionally regulates growth of all three PDAC cell lines in collagen. BET inhibitors and BRD4 siRNA repress HMGA2, an architectural protein that modulates chromatin state and also contributes to chemoresistance, in PDAC cells grown in collagen. Importantly, we show that there is a statistically significant correlation between BRD4 and HMGA2 in human PDAC tumors. Significantly, overexpression of HMGA2 partially mitigates the effect of BET inhibitors on growth and c-MYC and/or FOSL1 expression in collagen. Overall, these results demonstrate that BET inhibitors block growth of PDAC cells in collagen and that BET proteins may be potential targets for the treatment of pancreatic cancer. Mol Cancer Ther; 13(7); 1907–17. ©2014 AACR.

Three-dimensional collagen I promotes gemcitabine resistance in vitro in pancreatic cancer cells through HMGA2-dependent histone acetyltransferase expression.

Pancreatic ductal adenocarcinoma (PDAC) is associated with a pronounced collagen-rich stromal reaction that has been shown to contribute to chemo-resistance. We have previously shown that PDAC cells are resistant to gemcitabine chemotherapy in the collagen microenvironment because of increased expression of the chromatin remodeling protein high mobility group A2 (HMGA2). We have now found that human PDAC tumors display higher levels of histone H3K9 and H3K27 acetylation in fibrotic regions. We show that relative to cells grown on tissue culture plastic, PDAC cells grown in three-dimensional collagen gels demonstrate increased histone H3K9 and H3K27 acetylation, along with increased expression of p300, PCAF and GCN5 histone acetyltransferases (HATs). Knocking down HMGA2 attenuates the effect of collagen on histone H3K9 and H3K27 acetylation and on collagen-induced p300, PCAF and GCN5 expression. We also show that human PDAC tumors with HMGA2 demonstrate increased histone H3K9 and H3K27 acetylation. Additionally, we show that cells in three-dimensional collagen gels demonstrate increased protection against gemcitabine. Significantly, down-regulation of HMGA2 or p300, PCAF and GCN5 HATs sensitizes the cells to gemcitabine in three-dimensional collagen. Overall, our results increase our understanding of how the collagen microenvironment contributes to chemo-resistance in vitro and identify HATs as potential therapeutic targets against this deadly cancer.

Snail cooperates with KrasG12D to promote pancreatic fibrosis

Patients with pancreatic cancer, which is characterized by an extensive collagen-rich fibrotic reaction, often present with metastases. A critical step in cancer metastasis is epithelial-to-mesenchymal transition (EMT), which can be orchestrated by the Snail family of transcription factors. To understand the role of Snail (SNAI1) in pancreatic cancer development, we generated transgenic mice expressing Snail in the pancreas. Because chronic pancreatitis can contribute to pancreatic cancer development, Snail-expressing mice were treated with cerulein to induce pancreatitis. Although significant tissue injury was observed, a minimal difference in pancreatitis was seen between control and Snail-expressing mice. However, because Kras mutation is necessary for tumor development in mouse models of pancreatic cancer, we generated mice expressing both mutant KrasG12D and Snail (Kras+/Snail+). Compared with control mice (Kras+/Snai−), Kras+/Snail+ mice developed acinar ectasia and more advanced acinar-to-ductal metaplasia. The Kras+/Snail+ mice exhibited increased fibrosis, increased phosphorylated Smad2, increased TGF-β2 expression, and activation of pancreatic stellate cells. To further understand the mechanism by which Snail promoted fibrosis, we established an in vitro model to examine the effect of Snail expression in pancreatic cancer cells on stellate cell collagen production. Snail expression in pancreatic cancer cells increased TGF-β2 levels, and conditioned media from Snail-expressing pancreatic cancer cells increased collagen production by stellate cells. Additionally, inhibiting TGF-β signaling in stellate cells attenuated the conditioned media–induced collagen production by stellate cells. Together, these results suggest that Snail contributes to pancreatic tumor development by promoting fibrotic reaction through increased TGF-β signaling. Implications: Expression of the EMT regulator Snail in the context of mutant Kras provides new insight into pancreatic cancer progression. Mol Cancer Res; 11(9); 1078–87. ©2013 AACR.

Targeting bet bromodomain proteins in solid tumors

There is increasing interest in inhibitors targeting BET (bromodomain and extra-terminal) proteins because of the association between this family of proteins and cancer progression. BET inhibitors were initially shown to have efficacy in hematologic malignancies; however, a number of studies have now shown that BET inhibitors can also block progression of non-hematologic malignancies. In this Review, we summarize the efficacy of BET inhibitors in select solid tumors; evaluate the role of BET proteins in mediating resistance to current targeted therapies; and consider potential toxicities of BET inhibitors. We also evaluate recently characterized mechanisms of resistance to BET inhibitors; summarize ongoing clinical trials with these inhibitors; and discuss potential future roles of BET inhibitors in patients with solid tumors.

Snail Cooperates with KrasG12D In Vivo to Increase Stem Cell Factor and Enhance Mast Cell Infiltration

Pancreatic ductal adenocarcinoma (PDAC) is associated with a pronounced fibro-inflammatory stromal reaction that contributes to tumor progression. A critical step in invasion and metastasis is the epithelial-to-mesenchymal transition (EMT), which can be regulated by the Snail family of transcription factors. Overexpression of Snail (Snai1) and mutant KrasG12D in the pancreas of transgenic mice, using an elastase (EL) promoter, resulted in fibrosis. To identify how Snail modulates inflammation in the pancreas, we examined the effect of expressing Snail in EL-KrasG12D mice (KrasG12D/Snail) on mast cell infiltration, which has been linked to PDAC progression. Using this animal model system, it was demonstrated that there are increased numbers of mast cells in the pancreas of KrasG12D/Snail mice compared with control KrasG12D mice. In addition, it was revealed that human primary PDAC tumors with increased Snail expression are associated with increased mast cell infiltration, and that Snail expression in these clinical specimens positively correlated with the expression of stem cell factor (SCF/KITLG), a cytokine known to regulate mast cell migration. Concomitantly, SCF levels are increased in the KrasG12D/Snail mice than in control mice. Moreover, overexpression of Snail in PDAC cells increased SCF levels, and the media conditioned by Snail-expressing PDAC cells promoted mast cell migration. Finally, inhibition of SCF using a neutralizing antibody significantly attenuated Snail-induced migration of mast cells. Implications: Together, these results elucidate how the EMT regulator Snail contributes to inflammation associated with PDAC tumors. Mol Cancer Res; 12(10); 1440–8. ©2014 AACR.

Abstract A10: Biomarker independant microfluidic Labyrinth for the high throughput enrichment and characterization of circulating tumor cells in pancreatic cancer

Introduction and Objective: Pancreatic cancer is a devastating disease with a 5-year survival rate of less than 6%. By the time of diagnosis, less than 15% of patients have surgically resectable tumors, which is one reason why it has the highest mortality rate among all cancer types. Emerging evidence has pointed the importance of circulating tumor cells (CTCs) in the spread of cancers and metastasis. CTCs are believed to be the most promising cancer biomarkers available in blood. Recent reports also show that these cells could be a good surrogate biomarker for not only prognosis, but also for cancer detection and development of personalized treatment. We have developed an inertial microfluidic-based separation technique for high throughput and label-free isolation of CTCs. Methods: To investigate the isolation efficiency of our technology before running cancer patients’ samples, PANC-1 cells labeled with cell tracker dye were spiked into 1 mL of whole blood. Using this optimized platform we isolate CTCs from pancreatic cancer patients, followed by downstream analysis . CTCs are characterized using immunocytochemistry for heterogeneity studies among CTC population. Results: Our microfluidic device consists of a size based separation platform in which CTCs are separated from other blood components. This high throughput label free separation device was designed and developed by our lab. After more than 20 generations of device revision, an optimized flow rate of 2.5 ml/min for PANC-1 pancreatic cancer cell line has yielded a 95% recovery of these cells from whole blood, with cancer cells traveling to the second outlet and 80% of the White Blood Cells (WBC) to the first outlet. We have successfully isolated CTCs from over 100 pancreatic cancer patients. Among several patients we were able to characterize different subpopulations using the epithelial marker CK-19 and EpCAM, and the EMT-like marker ZEB1. Conclusion: The implementation of our engineering technology to the study of pancreatic cancer can present novel ways to confront major hurdles in cancer research, such as early detection and the lack of effective therapeutics. The isolation and expansion of CTCs, the heterogeneous population of cells that promote metastasis, can provide meaningful information to elucidate the process of pancreatic tumorigenesis to preempt its fatal result. Citation Format: Lianette Rivera-Baez, Eric Lin, Meghna Waghray, Shamileh Fouladdel, Ebrahim Azizi, Max Wicha, Vaibhav Sahai, Diane Simeone, Sunitha Nagrath.{Authors}. Biomarker independant microfluidic Labyrinth for the high throughput enrichment and characterization of circulating tumor cells in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A10.

A phase II trial of y-90 radioembolization in patients with progressive hepatic metastases from neuroendocrine carcinoma at an NCI-designated comprehensive cancer center.

312 Background: Patients with neuroendocrine carcinoma mostly present with symptomatic metastatic disease due to mass effect or release of biologically active polypeptides or amines and have a 5-year survival rate of 22%. The objective of this study was to assess the efficacy of hepatic artery radioembolization with Yttrium (Y)-90 microspheres in patients with unresectable progressive hepatic metastasis from neuroendocrine tumors. Methods: We conducted a prospective, single institutional, one-arm phase II study at an NCI-designated comprehensive cancer center. The primary endpoint was 6-month progression-free survival (PFS). Secondary endpoints included objective overall response rate (ORR), 1-year overall survival (OS) rate and safety and toxicity profile. Results: A total of 22 patients were enrolled between July 2007 and September 2009 with ECOG performance status 0-1, 45% males and median age of 62.5 (28-88) years. Histology included small bowel carcinoid (n=12), pancreatic neuroendocrine (n=7) and ne...

Abstract 2449: The bromodomain inhibitor JQ1 blocks growth of pancreatic cancer cells in 3D collagen.

Pancreatic ductal adenocarcinoma (PDAC) is associated with a pronounced collagen-rich stromal reaction that has been shown to contribute to chemo-resistance. We have found that the collagen microenvironment promotes expression of histone acetyltransferases (HATs) and thereby promotes chemo-resistance; however, HATs have proven to be difficult ‘druggable’ targets. Bromodomain proteins are chromatin readers that can bind to acetylated histones and thereby regulate gene expression. JQ1, an inhibitor of BET class of human bromodomains, was shown to have efficacy against leukemia and lymphoma cell lines. Thus, we examined the effect of JQ1 on a panel of PDAC cells grown in 3D collagen. AsPC1, CD18 and Panc02.03 cells were particularly sensitive to the effects of JQ1, while Panc1 cells were relatively resistant to JQ1 treatment. JQ1 decreased myc mRNA and increased p21 mRNA in CD18 cells, but not in Panc1 cells. JQ1 also decreased growth of chemo-resistant CD18 cells grown in 3D collagen, and blocked EGF and TGF-β1-induced growth and scattering of Panc1 and CD18 cells in 3D collagen. The MEK1/2 inhibitor U0126 and JQ1 synergistically attenuated growth of CD18 and Panc1 cells in 3D collagen. In addition, EGFR inhibitors (AG1478 and PD153035) and JQ1 also synergistically attenuated the growth of CD18 and Panc1 cells in 3D collagen. In contrast, the p38 MAPK inhibitor SB202190 did not attenuate the effect of JQ1 on growth of CD18 and Panc1 cells in 3D collagen. Finally, JQ1 potentiated the effect of gemcitabine on the growth of CD18 and Panc1 cells in 3D collagen. Overall, these results suggest that JQ1 and other bromodomain inhibitors are potential therapeutic agents for the treatment of pancreatic cancer. Citation Format: Vaibhav Sahai, Krishan Kumar, Kazumi Ebine, Halla Nimeiri, Hidayatullah G. Munshi. The bromodomain inhibitor JQ1 blocks growth of pancreatic cancer cells in 3D collagen. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2449. doi:10.1158/1538-7445.AM2013-2449

Abstract 1517: Pancreatic stellate cells and chemoresistant pancreatic cancer cells induce EMT gene expression in normal pancreatic ductal cells.

Pancreatic cancer, one of the deadliest of human cancers, is associated with a collagen-rich pronounced stromal reaction. Previously, we showed that the collagen microenvironment increased the motility of human pancreatic ductal epithelial (HPDE) cells (Ottaviano AJ et al, Cancer Research 2006). Since stellate cells are one of the major contributors to the stromal reaction, we examined the effect of stellate cells on HPDE cells. HPDE cells were labeled with cell tracking dye and then co-cultured stellate cells to allow intimate cell-cell contact. HPDE cells were then isolated 72 hours later using FACS and changes in gene expression analyzed by real time PCR. We found that HPDE cells upregulated expression of epithelial-mesenchymal transition (EMT) markers Zeb1, Snail and vimentin. Stellate cells also increased expression of these EMT markers in HPDE cells expression Kras (HPDE-Kras). However, no change in these EMT markers were seen when the HPDE and stellate cells were prevented from direct cell-cell contact using transwell co-culture system. Treatment with TGF-b type I receptor inhibitor SB431542 blocked the effect of stellate cells on HPDE gene expression. Since ductal cells also encounter malignant cells in vivo, we also examined the effect of co-culture of ductal cells with cancer cells. HPDE cells failed to upregulate EMT markers when they were co-cultured with HPAFII/CD18 cell. However, when HPDE cells were co-cultured with chemo-resistant CD18 cells (CD18-CR), HPDE cells upregulated EMT markers. The effect of CD18-CR cells on HPDE gene expression was only observed when there was intimate cell-cell contact. Also, treatment with SB431542 blocked the effect on HPDE gene expression. These results indicate that the tumor microenvironment may affect the behavior of peri-tumoral non-malignant cells and thereby contribute to tumor progression. Citation Format: Krishan Kumar, Vaibhav Sahai, Kazumi Ebine, Hidayatullah G. Munshi. Pancreatic stellate cells and chemoresistant pancreatic cancer cells induce EMT gene expression in normal pancreatic ductal cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1517. doi:10.1158/1538-7445.AM2013-1517