Abstract A112: Eradication of cancer stem-like cells in PDAC

Abstract

Abstract Background: Pancreatic Ductal Adenocarcinoma (PDAC) is resistant to conventional chemotherapy. Cancer Stem-Like Cells (CSLCs) are drug resistant and can act as tumor initiating cells. Evidence suggests that CSLCs can be selected by chemotherapy that targets the more sensitive somatic cancer cells. In the current study we found that Gem treatment can not only select CSLCs, but can also induce transformation of somatic cancer cells into CSLCs. We also observed that p21 is required to maintain CSLCs in a quiescent state. Methods: Cell growth, cell cycle and apoptosis were analyzed by using MTS and FACS analysis. ALDH and p21 were localized by immunohistochemistry and immunofluorescence. CLSCs were analyzed by ALDH assay, clonogenic in vitro assays and in vivo tumor initiation. Both in vitro and in vivo silencing of p21 was accomplished using nanoparticle coupled siRNA. Results: Gem treatment induced the p21 and led to a transient cytostasis and chemoresistance in PDAC cell lines. Analysis of resected tumor samples revealed that Gem treatment also induced p21 expression and ALDH positivity in tumors of Gem treated but not untreated patients. In vitro studies indicated that Gem induced the acquisition of a CSLC phenotype and the expression of pluripotent transcription factors (PFTs). Silencing of p21 blocked the both basal and Gem induced CSLC numbers, the maintenance of quiescence, and resistance to Gem in vitro. In vivo, silencing of p21 greatly increased the effectiveness of Gem treatments to inhibit tumor growth and did not increase toxicity. Conclusion: These data indicate that p21 maintains chemotherapy induced CSLCs quiescence and drug resistance such that targeting p21 in combination with cytotoxic therapies is beneficial in eradicating both basal and Gem transformed CSLCs. Note: This abstract was not presented at the conference. Citation Format: Thiruvengadam Arumugam, Vijaya Ramachandran, Craig Logsdon. Eradication of cancer stem-like cells in PDAC. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A112.