BZW2 Inhibition Reduces Colorectal Cancer Growth and Metastasis

Because survival of patients with metastatic colorectal cancer remain poor, there is an urgent need to identify potential novel druggable targets that are associated with colorectal cancer progression. One such target, basic leucine zipper and W2 domains 2 (BZW2), is involved in regulation of protein translation, and its overexpression is associated with human malignancy. Thus, we investigated the expression and regulation of BZW2, assessed its role in activation of WNT/β-catenin signaling, identified its downstream molecules, and demonstrated its involvement in metastasis of colorectal cancer. In human colorectal cancers, high mRNA and protein expression levels of BZW2 were associated with tumor progression. BZW2-knockdown reduced malignant phenotypes, including cell proliferation, invasion, and spheroid and colony formation. BZW2-knockdown also reduced tumor growth and metastasis; conversely, transfection of BZW2 into BZW2 low-expressing colorectal cancer cells promoted malignant features, including tumor growth and metastasis. BZW2 expression was coordinately regulated by microRNA-98, c-Myc, and histone methyltransferase enhancer of zeste homolog 2 (EZH2). RNA sequencing analyses of colorectal cancer cells modulated for BZW2 identified P4HA1 and the long noncoding RNAs, MALAT1 and NEAT1, as its downstream targets. Further, BZW2 activated the Wnt/β-catenin signaling pathway in colorectal cancers expressing wild-type β-catenin. In sum, our study suggests the possibility of targeting BZW2 expression by inhibiting EZH2 and/or c-Myc.

IMPLICATIONS

FDA-approved small-molecule inhibitors of EZH2 can indirectly target BZW2 and because BZW2 functions as an oncogene, these inhibitors could serve as therapeutic agents for colorectal cancer.

Abstract P4-08-06: Clock Genes in Breast Cancer

Background: Disruption of circadian processes has been linked to cancer initiation, progression, metastasis, resistance, and mortality. Clock proteins are an emerging target for therapy in breast cancer. Circadian rhythms are controlled by a network of transcription/translation feedback loops primarily driven by BMAL and CLOCK and the transcriptional repressors period (PER1-3) and cryptochrome (CRY1-2). We investigated the molecular and clinical associations of clock genes in breast cancer. Methods: A total of 9563 breast tumors underwent molecular profiling (Caris Life Sciences). Analyses included next-generation sequencing of DNA (592 genes-NextSeq, WES-NovaSeq) and RNA (NovaSeq). Clock gene Score (CS) was determined using expression of clock pathway gene Z scores (positives of BMAL, CLOCK and negatives of PER1/2 and CRY1/2) and then stratified into quartiles. xCell was used to quantify immune cell infiltration in the tumor microenvironment (TME). ER/PR was tested by IHC and HER2 was tested by either IHC or CISH. Significance was determined as P values adjusted for multiple comparison (Q) of < 0.05. Real-world survival information was obtained from insurance claims data and was calculated from either tissue collection to last contact or time on treatment (TOT); comparison was done by Kaplan-Meier test. Results: TNBC had the highest median CS score, while HR+/HER2- had the lowest CS (0.96 vs 0.26 q<.001). In TNBC, PDL1 was significantly associated with higher CS (56% Q4 vs 28% Q1, q<.05). TP53 mutation was associated with higher CS (88% Q4 vs 75% Q1), while CDH1 and STK11 mutations were associated with lower CS (3.4% Q4 vs 8.7% Q1 and 0.1% Q4 vs 2.2% Q1). For the TME (xCell) in TNBC, CD8+ T cells, B cells, monocytes and NK cells were positively associated with CS, whereas CD4+ central and effector memory T cells, eosinophils, and endothelial cells were associated with lower CS (Q1 vs Q4 all q<.05). In HR+/HER2- tumors, PDL1 was also associated with higher CS (24% Q4 vs 14% Q1, q<.05). TP53 mutations (39% Q4 vs 23% Q1), HMGA2 (2% Q4 vs 0.4% Q1) and LGR5 amplifications (3% Q4 vs 0.4% Q1), and LOH (WES) (35% Q4 vs 21% Q1) were associated with higher CS. CDH1(12% Q4 vs 23% Q1), KMT2C (6% Q4 vs 10% Q1) and PIK3CA mutations (37% Q4 vs 45% Q1) were associated with lower CS (all q<.05). In HR+/HER2- tumors there was a decrease in CD4+ central memory cells, common myeloid progenitor cells, endothelial cells, and eosinophils in high CS tumors. Activated myeloid dendritic cells, B cells, CD4+ memory T cells, CD8+ naïve T cells, M1 macrophages, and Tregs all had higher abundance in high CS tumors. In HR+/HER2+ tumors, PDL1 trended positively with CS but did not reach significance likely due to sample size. For all tumors, PDL1 expression positively correlated with CS (17% Q1 vs 37% Q4) while ER (75% Q1 vs 55% Q4) and PR (49% Q1 vs 38% Q4, all q<.05) were negatively associated; no association was seen with HER2. Expression of TIMELESS (HR:0.7, CI: 0.65-0.77) and CLOCK (HR: 0.8, CI: 0.72-0.86) below median were associated with longer OS, while expression of CRY2 (HR: 1.4, CI: 1.3-1.6); PER2/3 (HR: 1.1, CI:1.0-1.2; HR:1.3, CI:1.2-1.4) above median was associated with longer OS. In TNBC, TOT IO therapy was prolonged with higher expression of CLOCK (HR: 0.5, CI: 0.41-0.72), TIMELESS (HR: 0.7 CI: 0.53-0.91), ARNTL (HR: 0.7 CI:0.54-0.92) and CRY1/2 (HR: 0.6, CI: 0.46-0.80; HR: 0.75 CI: 0.57-0.98). Conclusions: Dysregulation of clock genes is strongly associated with breast cancer subtype and survival. Higher CS is associated with TNBC and PDL1 expression and supports the use of checkpoint inhibitors. Prognosis is better with low expression of TIMELESS and CLOCK and high expression of CRY2 and PER2/3, suggesting a role in tumor development and maintenance. HR+/HER2- tumors have lowest CS, fitting with less aggressive phenotype and better prognosis. Clock genes are novel predictive and prognostic molecular markers and emerging targets for the development of new treatments in breast cancer.

Citation Format: Priya Jayachandran, Yasmine Baca, Joanne Xiu, Yuanzhong Pan, Phil Walker, Francesca Battaglin, Hiroyuki Arai, Moh’d Khushman, Janice Lu, Darcy Spicer, Shannon Mumenthaler, Richard Goldberg, Benjamin Weinberg, Emil Lou, Michael Hall, Arielle L. Heeke, W. Michael Korn, Steve A. Kay, Heinz-Josef Lenz, Evanthia T. Roussos Torres. Clock Genes in Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-08-06.

Patient-reported geriatric assessment-based frailty index among older adults with gastrointestinal malignancies

BACKGROUND

Older adults with cancer are at increased risk of treatment-related toxicities and excess mortality. We evaluated whether a patient-reported geriatric assessment (GA) based frailty index can identify those at risk of adverse outcomes.

METHODS

Older adults (≥60 years) enrolled in a single-institutional prospective registry underwent patient-reported GA at initial evaluation in our medical oncology clinic. Using deficit accumulation method, we constructed a 44-item frailty index (CARE-FI), categorizing patients as robust, pre-frail, and frail. The primary outcome was overall survival (OS). Secondary outcomes included (a) functional decline at 3 months post-therapy (b) incident grade ≥3 treatment-related toxicities at six-month post-treatment. We used multivariate Cox and logistic regression models respectively to study the impact of frailty on primary and secondary outcomes.

RESULTS

We identified 589 older adults with a median age of 69 years; 55% males and 73% Whites. Overall, 168 (29%) were pre-frail and 230 (39%) frail. Being frail (vs. robust) was associated with worse OS (Hazards Ratio, HR 1.83, 95% Confidence Interval, CI 1.34-2.49, p < 0.001) after adjusting for age, sex, race/ethnicity, cancer type, cancer stage, and line of therapy. Similarly, frailty was associated with increased risk of functional decline (OR 3.01; 95% CI 1.33-6.81; p = 0.008) and grade ≥3 non-hematologic toxicities (OR 3.65; 95% CI 1.54-8.69; p = 0.003) but not hematologic toxicities (OR 1.01; 95% CI 0.46-2.22; p = 0.97).

CONCLUSIONS

Our frailty index using a patient-reported GA is a robust predictor of survival, functional decline, and treatment related toxicity among older adults with GI malignancies.

DCZ0415, a small-molecule inhibitor targeting TRIP13, inhibits EMT and metastasis via inactivation of the FGFR4/STAT3 axis and the Wnt/β-catenin pathway in colorectal cancer

Thyroid receptor-interacting protein 13 (TRIP13), a protein of the AAA-ATPase family, is upregulated in various human cancers, including colorectal cancer (CRC). This study focused on the inhibition of TRIP13-induced CRC progression and signalling by DCZ0415, a small molecule targeting TRIP13. It demonstrated potent antitumour activity in TRIP13-deregulated cancer cell lines, regardless of their p53, KRAS, BRAF, epidermal growth factor receptor or microsatellite instability status. The treatment of CRC cells with DCZ0415 resulted in decreased cell proliferation, induced cell cycle arrest in the G2-M phase and increased apoptosis. DCZ0415 diminished xenograft tumour growth and metastasis of CRC in immunocompromised mice. DCZ0415 reduced expression of fibroblast growth factor receptor 4 (FGFR4), signal transducer and activator of transcription 3 (STAT3), and proteins associated with the epithelial-mesenchymal transition and nuclear factor kappa B (NF-κB) pathways in cells and xenografts exhibiting high expression of TRIP13. Additionally, DCZ0415 decreased cyclin D1, β-catenin and T-cell factor 1, leading to the inactivation of the Wnt/β-catenin pathway. In a syngeneic CRC model, DCZ0415 treatment induced an immune response by decreasing PD1 and CTLA4 levels and increasing granzyme B, perforin and interferon gamma. In sum, DCZ04145 inhibits the TRIP13-FGFR4-STAT3 axis, inactivates NF-κB and Wnt/β-catenin signalling, activates antitumour immune response and reduces the progression and metastasis of CRC. This study provides a rationale to evaluate DCZ0415 clinically for the treatment of a subset of CRCs that exhibit dysregulated TRIP13 and FGFR4.

Distinct genomic landscapes of gastroesophageal adenocarcinoma depending on PD-L1 expression identify mutations in RAS-MAPK pathway and TP53 as potential predictors of immunotherapy efficacy

BACKGROUND

The impact of molecular alterations on programmed death-ligand 1 (PD-L1) combined positive score (CPS) is not well studied in gastroesophageal adenocarcinomas (GEAs). We aimed to characterize genomic features of tumors with different CPSs in GEAs.

PATIENTS AND METHODS

Genomic alterations of 2518 GEAs were compared in three groups (PD-L1 CPS ≥ 10, high; CPS = 1-9, intermediate; CPS < 1, low) using next-generation sequencing. We assessed the impact of gene mutations on the efficacy of immune checkpoint inhibitors (ICIs) and tumor immune environment based on the Memorial Sloan Kettering Cancer Center and The Cancer Genome Atlas databases.

RESULTS

High, intermediate, and low CPSs were seen in 18%, 54% and 28% of GEAs, respectively. PD-L1 positivity was less prevalent in women and in tissues derived from metastatic sites. PD-L1 CPS was positively associated with mismatch repair deficiency/microsatellite instability-high, but independent of tumor mutation burden distribution. Tumors with mutations in KRAS, TP53, and RAS-mitogen-activated protein kinase (MAPK) pathway were associated with higher PD-L1 CPSs in the mismatch repair proficiency and microsatellite stability (pMMR&MSS) subgroup. Patients with RAS-MAPK pathway alterations had longer overall survival (OS) from ICIs compared to wildtype (WT) patients [27 versus 13 months, hazard ratio (HR) = 0.36, 95% confidence interval (CI): 0.19-0.7, P = 0.016] and a similar trend was observed in the MSS subgroup (P = 0.11). In contrast, patients with TP53 mutations had worse OS from ICIs compared to TP53-WT patients in the MSS subgroup (5 versus 21 months, HR = 2.39, 95% CI: 1.24-4.61, P = 0.016).

CONCLUSIONS

This is the largest study to investigate the distinct genomic landscapes of GEAs with different PD-L1 CPSs. Our data may provide novel insights for patient selection using mutations in TP53 and RAS-MAPK pathway and for the development of rational combination immunotherapies in GEAs.

Exosomal Formulation Escalates Cellular Uptake of Honokiol Leading to the Enhancement of Its Antitumor Efficacy

Honokiol is a phytochemical isolated from the Magnolia plant. It exhibits significant antitumor activity against a variety of cancer cell types via targeting of critical mediators of tumor progression, stromal remodeling, and chemoresistance. However, poor bioavailability and inefficient tumor uptake remain some of the hurdles in its translation as a therapeutically useful drug. Here, we developed a nanoformulation of honokiol using mesenchymal stem cell-derived exosomes, which are nonimmunogenic and express surface markers to support their tumor-targeted delivery. Maximum entrapment of honokiol occurred when it was mixed in a 1:4 weight ratio with exosomes and subjected to six cycles of sonication. Dynamic light scattering analysis demonstrated that the average size (∼175.3 nm), polydispersity (∼0.11), and integrity (∼12.9 mV) of exosomes remained in the desirable range post honokiol encapsulation. Exosome-encapsulated honokiol exhibited significantly higher therapeutic efficacy over the free honokiol in WST-1 growth and long-term clonogenicity assays. Flow cytometry-based cell cycle and live/dead cell assay, respectively, confirmed the enhanced effect of exosomal honokiol formulation on cell cycle arrest and apoptosis induction. More significant alterations in the expression of cell cycle- and survival-associated proteins were also observed in cancer cells treated with exosomal honokiol over free honokiol. Higher intracellular accumulation of honokiol was recorded in cancer cells treated with equivalent doses of honokiol as compared to the free honokiol. Together, our work is the first demonstration of exosomal encapsulation of honokiol and its improved antitumor efficacy resulting from improved cellular uptake.

Prolonged response to liposomal irinotecan in a patient with stage IV pancreatic/bile duct cancer previously treated with FOLFIRINOX and gemcitabine plus nab-paclitaxel

At 9%, and 2% when diagnosed at advanced stage, the 5-year relative survival rate for pancreatic ductal adenocarcinoma (pdac) is the lowest of any cancer. The currently approved treatment options for metastatic pdac in the United States are folfirinox [irinotecan-fluorouracil (5fu)-leucovorin (lv)-oxaliplatin], gemcitabine-nab-paclitaxel, and liposomal irinotecan plus 5fu-lv. Liposomal irinotecan is a novel formulation of irinotecan encapsulated within a lipid bilayer, which favours local metabolic activation. The napoli-1 trial demonstrated the efficacy of liposomal irinotecan in combination with 5fu and lv for the treatment of advanced pdac after progression on gemcitabine-based chemotherapy. The 1-year survival in those patients was 25%; however, none had had irinotecan-refractory disease before treatment with liposomal irinotecan. Furthermore, the U.S. National Comprehensive Cancer Network guidelines recommend liposomal irinotecan plus 5fu-lv in patients who have received prior fluoropyrimidine-based therapy if no prior irinotecan therapy has been given. Here, we report a male patient with stage iv cancer of pancreas or bile duct (site unconfirmed) who experienced a prolonged (51 weeks) response to liposomal irinotecan plus 5fu-lv despite prior disease progression on irinotecan. Several factors have previously been associated with long-term survival in patients receiving liposomal irinotecan therapy: no prior irinotecan-based chemotherapy, high Karnofsky performance status score, age 65 years or less, serum carbohydrate antigen 19-9 less than 59 U/mL, neutrophil-to-lymphocyte ratio 5 or less, and absence of liver metastasis. The patient in the present report had none of those characteristics indicative of long-term survival, except his age at diagnosis-47 years.

The Correlation Between DPYD*9A(c.85T>C) Genotype and Dihydropyrimidine Dehydrogenase Deficiency Phenotype in Patients With Gastrointestinal Malignancies Treated With Fluoropyrimidines

Introduction

The correlation between DPYD*9A (c.85T>C) genotype and dihydropyrimidine dehydrogenase (DPD) deficiency phenotype is controversial. In a cohort of 28 patients, DPYD*9A was the most commonly diagnosed variant (46%) and there was a noticeable genotype-phenotype correlation. Here we genotyped a larger cohort of a mixed racial background to explore the incidence of DPYD*9A variant and to further study the genotype-phenotype correlation.

Methods

Genotyping for high-risk DPYD variants (DPYD*2A, DPYD*13, and DPYD*9B) and the DPYD*9A variant was performed on 113 patients with gastrointestinal malignancies (GI) treated with fluoropyrimidines, using TaqMan chemistry. The prevalence of different DPYD variants was further analyzed in 1,283 retrospective data from ARUP laboratories. Fluoropyrimidines-associated toxicity was graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (v 5.0). Fisher’s exact test was used for statistical analysis.

Results

In total, 1,283 were retrospectively reviewed for DPYD variants. Four patients (0.31%) carried DPYD c.-1590T>C, 10 patients (0.55%) carried DPYD c.1679T>G (*13), 36 patients (2.8%) carried DPYD c.2846A>T, and 527 patients (41.1%) carried DPYD c.85T>C (*9A). In the GI cancer cohort, DPYD variants were identified in 61 patients (54%), showing similar prevalence as the retrospective analysis. Caucasians represented 54% and African Americans represented 43%. Twenty-eight patients (46%) were females. Heterozygous DPYD*9A was identified in 46 patients (41%) and homozygous DPYD*9A was identified in 11 patients (10%). DPYD*2A was identified in 3 patients and DPYD*9B was identified in 2 patients (one patient had double heterozygous *9A and *9B). Grade 3 to 4 toxicities were experienced in 26 patients with mutant DPYD*9A (3 patients had homozygous DPYD*9A) and in 20 patients with no identified DPYD mutation (P = .7035). In patients who received full-dose fluoropyrimidines (N = 85), grade 3 to 4 toxicities were experienced in 22 patients with mutant DPYD*9A (2 patients had homozygous DPYD*9A) and in 17 patients with no identified DPYD mutation (P = .8275).

Conclusion

In the GI cancer population, the DPYD*9A variant was identified in 54% of patients. The correlation between DPYD*9A variant and DPD clinical phenotype was not significant. The noticeable correlation that was previously reported is likely due to small sample size and selection bias.

Abstract 1911: Bi-directional cross-talk of pancreatic cancer and stellate cells, mediated through CXCR4 and hedgehog pathways, promotes chemoresistance via its effect on gemcitabine metabolism, ROS detoxification and cancer stemness

Mounting evidence suggests that tumor-stromal interactions play a key role in pancreatic cancer (PC) pathogenesis and chemoresistance. We previously demonstrated that CXCL12, a chemokine secreted by activated pancreatic stellate cells (PSCs), promoted PC chemoresistance upon binding to its receptor CXCR4. Furthermore, activation of CXCL12/CXCR4 pathway in PC cells (PCCs) also increased the expression and secretion of sonic hedgehog (SHH), which is a known inducer of PSCs thus establishing a bi-directional tumor-stromal crosstalk. Here we present data to support that dual targeting of CXCL12/CXCR4 and hedgehog pathways is effective in improving therapeutic outcome in PC by diminishing multiple chemoresistance mechanisms. Monoculture of PCCs (MiaPaCa and Colo357) or coculture of PCCs and PSCs were treated with gemcitabine in the presence and absence of CXCR4 antagonist (AMD3100) and hedgehog inhibitor (GDC-0449). The data demonstrated that PCCs in coculture had better survival against gemcitabine treatment as compared to those grown in monoculture and inhibition of CXCL12/CXCR4 and hedgehog pathways abrogated this co-culture-induced chemoresistance. In further mechanistic studies, we identified co-culture-induced changes in gene expression and confirmed their functional significance in chemoresistance. Our data established important roles of genes associated with gemcitabine metabolism, ROS detoxification and stemness in PC chemoresistance. Inhibition of CXCL12/CXCR4 and hedgehog pathways led to increase in gemcitabine-mediated ROS production, enhanced accumulation of active gemcitabine metabolite (gemcitabine tri-phosphate) and reduced stemness in cocultured PCCs. Finally, we examined the efficacy of our dual targeting approach in vivo in an orthotopic mouse model of pancreatic cancer by treating the mice with gemcitabine alone or in combination with AMD3100 and/or GDC-0449. Our data demonstrated that mice treated with gemcitabine along with AMD3100 and/or GDC-0449 had significantly greater reduction in tumor growth as compared to those treated with gemcitabine only. Studies are ongoing in additional pancreatic tumor models. Together, these findings provide strong evidence in support of a novel combination therapy for pancreatic cancer treatment.

Citation Format: Mohammad Aslam Khan, Girijesh K. Patel, Sanjeev K. Srivastava, Sumit Arora, Haseeb Zubair, James Elliot Carter, Bin Wang, Seema Singh, Moh’d Khushman, Ajay P. Singh. Bi-directional cross-talk of pancreatic cancer and stellate cells, mediated through CXCR4 and hedgehog pathways, promotes chemoresistance via its effect on gemcitabine metabolism, ROS detoxification and cancer stemness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1911.

Syndrome of Inappropriate Anti-Diuretic Hormone Secretion Secondary to Strongyloides stercoralis Infection in an Allogeneic Stem Cell Transplant Patient: A Case Report and Literature Review

Syndrome of inappropriate anti-diuretic hormone (SIADH) has been reported to be associated with systemic Strongyloides stercoralis. Here, we report a case of a stem cell transplant (SCT) recipient who developed severe SIADH secondary to systemic S Stercoralis. The SIADH resolved quickly after treating the systemic S Stercoralis with ivermectin. A systematic review of the literature was performed by PubMed, Scopus, and Cochrane database search. Only eight cases of S Stercoralis in allogeneic SCT recipients have been previously reported. To our knowledge, ours is the first reported case of SIADH secondary to S Stercoralis infection in an allogeneic SCT recipient. Prior to transplantation, even if asymptomatic, patients from endemic regions should be screened with strongyloides immunoglobulin (Ig)G serology. Pretransplantation eosinophilia should be evaluated by screening multiple stool samples for ova and parasites. Transplant candidates with positive serology or stool tests can be treated pretransplantation to eradicate infection. Patients at risk for S Stercoralis who develop nonspecific gastrointestinal complaints, rash, pulmonary infiltrates, or gram-negative bacteremia or meningitis may have S Stercoralis hyperinfection syndrome. Our case indicates that the development of SIADH may be an additional clue to this diagnosis. Appropriate diagnostic studies, including repeat stool and other body fluid sampling, should be expedited and ivermectin therapy initiated rapidly to prevent significant morbidity and mortality.

Abstract 2116: Chemotherapy-induced exosomal secretion promotes chemoresistance in pancreatic cancer cells

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of death from cancer in the United States, with a dismal median survival rate of 2-8 months after diagnosis and a 5-year overall survival rate of ∼7%. It carries a notoriously poor prognosis due to advanced stage at presentation for most patients, lack of very effective therapy and development of resistance to available chemotherapy. Intercellular communication between tumor-tumor and tumor-nontumor cells is critical for tumor growth and progression. Extracellular vesicles (EVs) comprising of exosomes, microvesicles and apoptotic bodies are considered important mediators of intercellular communication and play pivotal roles in different physiological and pathological processes. However, role of EVs in the development of acquired resistance to chemotherapy in PDAC cells is largely unexplored. Here, we examined the role of EVs in chemotherapeutic resistance of PDAC cells.

Methods: Conditioned media from vehicle-treated and (V-CM) gemcitabine-treated PDAC cells (Gem-CM) were collected and fractionated into soluble (Gem-Sol) and vesicular (GEM-EV) factions. PDAC cells were pre-treated with Gem-CM, Gem-Sol and Gem-EV followed by treatment with various doses (0-20 μM) of gemcitabine for different time intervals (48 and 72 h). EVs were then separated by differential ultracentrifugation, size was determined using Dynamic Light Scattering (DLS) and assessed for their chemoresistance conferring activity in PDAC cells. Immunoblotting was performed to examine the specific markers associated with EVs.

Results: Both Gem-CM and Gem-EV provided significant protection to gemcitabine-treated cells, while Gem-Sol had only negligible effect. DLS based-size distribution analysis identified EVs of three different size viz. large (&gt; 1500 nm), medium (500-1500 nm) and small (100-300 nm). Treatment of large and medium sized Gem-EVs did not show any chemoprotective effect in PDAC cells, while smaller Gem-EVs provided remarkable survival benefits to PDAC cells against gemcitabine treatment. Immunoblot data revealed that these active EVs are enriched with CD9 and CD63, specific markers of exosomes. Interestingly, we observed that exosomes of gemcitabine-treated PDAC cells were larger than those secreted by vehicle treated cells. Moreover, the amount of exosomes in Gem-CM was significantly higher as comparison to the CM of vehicle-treated cells. Studies are being conducted to identify the cargo encapsulated by exosomes responsible for exosomes-mediated chemoresistance in PDAC cells.

Conclusion: Our findings suggest that chemotherapy induces secretion of exosomes in PDAC cells that enhances chemoresistance by spreading the molecular signals.

Citation Format: Girijesh K. Patel, Arun Bhardwaj, Sanjeev K. Srivastava, Mohammad Aslam Khan, Seema Singh, Moh’d Khushman, Ajay P. Singh. Chemotherapy-induced exosomal secretion promotes chemoresistance in pancreatic cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2116.