An unbiased high-throughput drug screen reveals a potential therapeutic vulnerability in the most lethal molecular subtype of pancreatic cancer

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is predicted to become the second leading cause of cancer-related deaths in the United States by 2020, due in part to innate resistance to widely used chemotherapeutic agents and limited knowledge about key molecular factors that drive tumor aggression. We previously reported a novel negative prognostic biomarker, keratin 17 (K17), whose overexpression in cancer results in shortened patient survival. In this study, we aimed to determine the predictive value of K17 and explore the therapeutic vulnerability in K17-expressing PDAC, using an unbiased high-throughput drug screen. Patient-derived data analysis showed that K17 expression correlates with resistance to Gemcitabine (Gem). In multiple in vitro models of PDAC, spanning human and murine PDAC cells, we determined that the expression of K17 results in a more than two-fold increase in resistance to Gem and 5-fluorouracil, key components of current standard-of-care chemotherapeutic regimens. Furthermore, through an unbiased drug screen, we discovered that Podophyllotoxin (PPT), a microtubule inhibitor, showed at least two-fold higher sensitivity in K17-expressing compared to K17-negative PDAC cells. In the clinic, another microtubule inhibitor, Paclitaxel (PTX), is used in combination with Gem as a first line chemotherapeutic regimen for pancreatic, breast, lung, and ovarian cancer. Surprisingly, we found that when combined with Gem, PPT but not PTX, was synergistic in inhibiting the viability of K17-expressing PDAC cells. This provides evidence that PPT or its derivatives could potentially be combined with Gem to enhance treatment efficacy for the approximately 50% of PDACs that express high levels of K17. In summary, we reported that K17 is a novel target for developing a biomarker-based personalized treatment for PDAC.