Carlos J. Diaz Osterman

Curcumin Modulates Pancreatic Adenocarcinoma Cell-Derived Exosomal Function

Pancreatic cancer has the highest mortality rates of all cancer types. One potential explanation for the aggressiveness of this disease is that cancer cells have been found to communicate with one another using membrane-bound vesicles known as exosomes. These exosomes carry pro-survival molecules and increase the proliferation, survival, and metastatic potential of recipient cells, suggesting that tumor-derived exosomes are powerful drivers of tumor progression. Thus, to successfully address and eradicate pancreatic cancer, it is imperative to develop therapeutic strategies that neutralize cancer cells and exosomes simultaneously. Curcumin, a turmeric root derivative, has been shown to have potent anti-cancer and anti-inflammatory effects in vitro and in vivo. Recent studies have suggested that exosomal curcumin exerts anti-inflammatory properties on recipient cells. However, curcumin’s effects on exosomal pro-tumor function have yet to be determined. We hypothesize that curcumin will alter the pro-survival role of exosomes from pancreatic cancer cells toward a pro-death role, resulting in reduced cell viability of recipient pancreatic cancer cells. The main objective of this study was to determine the functional alterations of exosomes released by pancreatic cancer cells exposed to curcumin compared to exosomes from untreated pancreatic cancer cells. We demonstrate, using an in vitro cell culture model involving pancreatic adenocarcinoma cell lines PANC-1 and MIA PaCa-2, that curcumin is incorporated into exosomes isolated from curcumin-treated pancreatic cancer cells as observed by spectral studies and fluorescence microscopy. Furthermore, curcumin is delivered to recipient pancreatic cancer cells via exosomes, promoting cytotoxicity as demonstrated by Hoffman modulation contrast microscopy as well as AlamarBlue and Trypan blue exclusion assays. Collectively, these data suggest that the efficacy of curcumin may be enhanced in pancreatic cancer cells through exosomal facilitation.

Enhancement of Gemcitabine sensitivity in pancreatic adenocarcinoma by novel exosome-mediated delivery of the Survivin-T34A mutant

Background: Current therapeutic options for advanced pancreatic cancer have been largely disappointing with modest results at best, and though adjuvant therapy remains controversial, most remain in agreement that Gemcitabine should stand as part of any combination study. The inhibitor of apoptosis (IAP) protein Survivin is a key factor in maintaining apoptosis resistance, and its dominant-negative mutant (Survivin-T34A) has been shown to block Survivin, inducing caspase activation and apoptosis. Methods: In this study, exosomes, collected from a melanoma cell line built to harbor a tetracycline-regulated Survivin-T34A, were plated on the pancreatic adenocarcinoma (MIA PaCa-2) cell line. Evaluation of the presence of Survivin-T34A in these exosomes followed by their ability to induce Gemcitabine-potentiative cell killing was the objective of this work. Results: Here we show that exosomes collected in the absence of tetracycline (tet-off) from the engineered melanoma cell do contain Survivin-T34A and when used alone or in combination with Gemcitabine, induced a significant increase in apoptotic cell death when compared to Gemcitabine alone on a variety of pancreatic cancer cell lines. Conclusion: This exosomes/Survivin-T34A study shows that a new delivery method for anticancer proteins within the cancer microenvironment may prove useful in targeting cancers of the pancreas.

Proteomic Profiling of Serum-Derived Exosomes from Ethnically Diverse Prostate Cancer Patients

ABSTRACT Prostate cancer (PCa) remains the most frequently diagnosed male malignancy in Western countries and the second most common cause of male cancer death in the United States. The relatively elevated PCa incidence and mortality among African American men makes this cancer type a challenging health disparity disease. To increase the chance for successful trea tment, earlier detection and prediction of tumor aggress iveness will be important and need to be resolved. This study demonstrates that small membrane-bound vesicles shed from the tumor called exosomes contain ethnically and tumor-specific biomarkers, and could be exploited for their diagnostic and therapeutic potential.

Exosomes Secreted from Human Cancer Cell Lines Contain Inhibitors of Apoptosis (IAP)

Exosomes are endosomal-derived nanovesicles released by normal and tumor cells which have been shown to transfer functionally active protein, lipids, mRNAs and miRNAs between cells. Varying in molecular profiles, biological roles, functional roles and protein contents, exosomes have been described as “multi-purpose carriers” playing a role in supporting the survival and growth of tumor cells. The IAP Survivin has been found to be present in tumor exosomes. However, the existence of other IAPs in tumor exosomes is still unknown. Survivin, cIAP1, cIAP2 and XIAP mRNA and protein are differently expressed in a panel of tumor cell lines: DLCL2, HeLa, MCF-7, Panc-1, and PC3. Exosomes were isolated from conditioned media collected from the cells from which RNA and protein were extracted. Our results provide evidence that like Survivin, XIAP, cIAP1 and cIAP2 proteins are found in tumor exosomes. The mRNA expression, however, is differentially expressed across the tumor cell lines. The presence of these bioactive molecules in exosomes may not only serve as warning signals, but also play a role in providing protection to the cancer cells against changes that are constantly occurring in the tumor microenvironment.

AML sensitivity to YM155 is modulated through AKT and Mcl-1

HL60 and U937 (acute myeloid leukemia (AML) cell lines) were assessed for sensitivity to YM155, and found to have distinct sensitive and resistant phenotypes, respectively. In HL60 cells, YM155 inhibition of growth proliferation was due to apoptosis which was measured by annexin V/PI staining. YM155 induced apoptosis through activation of intrinsic and extrinsic pathways that also culminated in caspase-3 activity and PARP cleavage. YM155 sensitivity was partially associated with this compounds ability to down-regulate survivin transcription since this was more pronounced in the HL60 cell line. However, marked differences were also observed in XIAP, Bcl-2, and Mcl-1L, and Mcl-1s. Furthermore, YM155 treatment completely inhibited production of total Akt protein in HL60, but not U937 cells. Importantly, Akt activity (pAkt-Ser473) levels were maintained in YM155 treated U937 cells which may help stabilize other anti-apoptotic proteins. Combination treatments with an Akt inhibitor, MK-2206, reduced levels of pAkt-Ser473 in U937 cells and synergistically sensitized them to YM155 cytotoxicity. Collectively our results indicate that Akt signaling may be an important factor mediating YM155 response in AML, and combinatorial therapies with Akt inhibitors could improve treatment efficacy in YM155-resistant cells.

Yin Yang 1 regulates the transcriptional repression of survivin

The mechanisms for regulation of the Inhibitor of Apoptosis (IAP) Survivin in cells undergoing stress associated with tumor development and the tumor microenvironment are not well understood. The stress response transcription factors HIF-1α and Yin Yang 1 (YY1) were hypothesized to contribute to the upregulation of Survivin in tumor cells. As expected, U2OS cells overexpressing HIF-1α showed a 2- to 3-fold transactivation when transfected. Surprisingly, when YY1 was overexpressed in this survivin promoter reporter system, luciferase expression was repressed 30- to 40-fold. YY1 involvement in survivin promoter repression was confirmed using siRNA directed against YY1. These studies showed that knockdown of YY1 releases the survivin promoter from the observed repression and leads to a 3- to 5-fold increase in promoter activity above basal levels. A U2OS cell line containing a stable YY1 Tet-off system was used to determine whether a temporal increase in YY1 expression affects Survivin protein levels. A low to moderate decrease in Survivin protein was observed 24h and 48h after Tet removal. Studies also confirmed that YY1 is capable of directly binding to the survivin promoter. Collectively, these findings identify novel basal transcriptional requirements of survivin gene expression which are likely to play important roles in the development of cancer and resistance to its treatment.

Cell death in response to antimetabolites directed at ribonucleotide reductase and thymidylate synthase

New agent development, mechanistic understanding, and combinatorial partnerships with known and novel modalities continue to be important in the study of pancreatic cancer and its improved treatment. In this study, known antimetabolite drugs such as gemcitabine (ribonucleotide reductase inhibitor) and 5-fluorouracil (thymidylate synthase inhibitor) were compared with novel members of these two drug families in the treatment of a chemoresistant pancreatic cancer cell line PANC-1. Cellular survival data, along with protein and messenger ribonucleic acid expression for survivin, XIAP, cIAP1, and cIAP2, were compared from both the cell cytoplasm and from exosomes after single modality treatment. While all antimetabolite drugs killed PANC-1 cells in a time- and dose-dependent manner, neither family significantly altered the cytosolic protein level of the four inhibitors of apoptosis (IAPs) investigated. Survivin, XIAP, cIAP1, and cIAP2 were found localized to exosomes where no significant difference in expression was recorded. This inability for significant and long-lasting expression may be a reason why pancreatic cancer lacks responsiveness to these and other cancer-killing agents. Continued investigation is required to determine the responsibilities of these IAPs in their role in chemoresistance in pancreatic adenocarcinoma.

Abstract 4856: Survivin packaging into exosomes is lipid raft-dependent

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA We have shown that Survivin is exported out of the cancer cell via exosomes despite its lack of a secretory signaling peptide. However, the mechanism of Survivin exosomal loading is not yet known. Exosomal protein sorting can be endosomal sorting complex required for transport (ESCRT)-dependent or ESCRT-independent. ESCRT dependent protein sorting requires monoubiquitination of the target protein, which serves as an exosome sorting signal. The ESCRT independent mechanism is through preferential aggregation of the proteins which is based on intrinsic physical properties to lipid-rafts present in exosomes. Our lab has recently shown that exosomal Survivin is associated with both Hsp70 and Hsp90, as well as PRDX1 which have also been shown associated with detergent-resistant lipid rafts. Here, we determine whether Survivin is lipid-raft dependent and whether Hsp70 and Hsp90 and/or PRDX1 are required for exosomal Survivin loading. Exosomes were collected from conditioned media taken from HeLaS cells and isolated by centrifugation. Colocalizations of Survivin with Hsp70, Hsp90 and PRDX1 in the cell and exosomes were detected by immnocytochemistry visualized by confocal microscopy and immunoprecipitation. HeLaS cells were treated with increasing concentrations of methyl-β-cyclodextrin to disrupt lipid rafts as a way to determine protein lipid raft association. Hsp70, Hsp90 and PRDX1 knock-down using siRNAs will be accomplished to verify the requirement of these proteins for Survivin exosome loading and lipid-raft dependents. Here we show that Survivin colocalizes with Hsp70, Hsp90 and PRDX1 in HeLaS cells as well as their exosomes. Increasing concentrations of methyl-β-cyclodextrin disrupts lipid rafts in the HeLaS cells and releases exosomes which also subsequently contain decreasing PRDX1 and Survivin protein amounts. The release of Survivin into the tumor microenvironment is an important finding as this IAP may contribute to the aggressiveness of the cancer as well as the development of chemoresistance. Despite lacking a secretory signaling peptide, Survivin is being released into the extracellular space via exosomes using chaperones. Knowing how Survivin is exosomally packaged may prove useful in selecting patient specific treatment regimens. Citation Format: Malyn May Asuncion Valenzuela, Heather R. Ferguson Bennit, Carlos Joel Diaz Osterman, Salma Khan, Carlos Casiano, Nathan R. Wall. Survivin packaging into exosomes is lipid raft-dependent. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4856. doi:10.1158/1538-7445.AM2014-4856

Abstract 3207: Curcumin induces pancreatic cancer cell death by targeting IAPs

Background Pancreatic cancer has among the highest mortality rates compared to other cancer types, with 94% of patients dying within five years of diagnosis. Contributing to the high mortality rate, patients with pancreatic cancer do not present significant symptoms until the disease is advanced. Moreover, treatment strategies have not improved substantially over the last decade. For this reason, a recent trend has led toward focusing on the use of herb-derived compounds, such as curcumin (turmeric derivative), to explore alternative treatments that will improve current pancreatic cancer therapy. Objective The objectives of this study were (1) to determine the effects of curcumin on pancreatic cancer cell metabolism, viability, cell cycle and morphology, and (2) to determine the mechanism by which curcumin induces cell death in pancreatic cancer cells by analyzing intracellular expression levels of inhibitor of apoptosis proteins (IAPs). Design/method Pancreatic adenocarcinoma cell lines (Panc-1 and MiaPaCa-2) were used to assess the effects of curcumin in pancreatic cancer. Effects on metabolism, viability and cell cycle were assayed by Alamar Blue, Trypan Blue and Propidium Iodide (PI) staining/flow cytometry (FACSCalibur). Morphological imaging was performed using Hoffman Modulation microscopy. Apoptosis was detected by Annexin V/PI flow cytometry (MACSQuant) and the expression of IAPs was assessed by Western blot. Results These data show that curcumin decreases pancreatic cancer cell metabolism and viability. Cell cycle stages were arrested in pancreatic cancer cells treated with curcumin compared to the non-treated controls. Apoptotic cells were detected by microscopy and confirmed by Annexin V/PI staining with subsequent flow cytometry analysis. IAPs levels are reduced in pancreatic cancer cell lines treated with curcumin compared to non-treated controls. Conclusion These results demonstrate that pancreatic adenocarcinoma cell lines are sensitive to curcumin treatment. Moreover, curcumin9s possible mechanism of action is inducing apoptosis by targeting IAPs. Collectively, these data suggest a potential role for curcumin in pancreatic cancer therapy. Citation Format: Carlos J. Diaz Osterman, Malyn May Asuncion Valenzuela, Heather R. Ferguson Bennit, Salma Khan, Nathan R. Wall. Curcumin induces pancreatic cancer cell death by targeting IAPs. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3207. doi:10.1158/1538-7445.AM2014-3207