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 and in vivo models of PDAC, spanning human and murine PDAC cells, and orthotopic xenografts, we determined that the expression of K17 results in a more than twofold 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 significantly higher sensitivity in K17‐positive compared to K17‐negative PDAC cell lines and animal models. In the clinic, another microtubule inhibitor, paclitaxel (PTX), is used in combination with Gem as a first‐line chemotherapeutic regimen for PDAC. Surprisingly, we found that when combined with Gem, PPT, but not PTX, was synergistic in inhibiting the viability of K17‐expressing PDAC cells. Importantly, in preclinical models, PPT in combination with Gem effectively decreased tumor growth and enhanced the survival of mice bearing K17‐expressing tumors. This provides evidence that PPT and its derivatives could potentially be combined with Gem to enhance treatment efficacy for the ~ 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.

Insight Into the Molecular Mechanism of Podophyllotoxin Derivatives as Anticancer Drugs

“…In a nutshell, the excellent selective therapeutic effect of PTOX and its derivatives on a variety of tumors has attracted increasing attention. Besides the above mentioned tumors, researchers have further developed more PTOX derivatives against other different cancers as well, including pancreatic cancer ( Pan et al, 2020 ), leukemia ( Zhang et al, 2016b ), head and neck squamous cell carcinoma (HNSCC) ( Resendez et al, 2019 ), cervical carcinoma ( Wang et al, 2013 ), etc.…”

Keratin 17 testing in pancreatic cancer needle aspiration biopsies predicts survival

“…Our laboratory is currently attempting to determine how testing the K17 status could serve as a predictive biomarker for currently available therapeutic agents for the most aggressive forms of PDAC. In a recent study, 19 we demonstrated that K17 expression correlates with the resistance of PDAC to gemcitabine, and using both in vitro and in vivo models with human and murine PDAC cells and orthotopic xenografts, we found that K17 expression drives increased resistance to gemcitabine and 5-fluorouracil, agents that are currently included in first-line chemotherapy for PDAC. Thus, determining the K17 status at the time of diagnosis could one day help to optimize therapeutic efficacy and to minimize the side effects attributable to agents that are unlikely to provide a survival advantage.…”

Genomic Heterogeneity of Pancreatic Ductal Adenocarcinoma and Its Clinical Impact

“…Thus, the assessment of surrogate markers by immunohistochemistry such as KRT81 and HNF1A [91], CFTR [92], and/or CDH17 and LGALS4 [110], have been proposed for the identification of exocrine-like (HNF1A+, CFTR+, CDH17+ and/or LGALS4+ tumors), squamous (KRT81+), and classical (negative for all above markers) [91,105] PDAC (Figure 3). In addition to KRT81, staining for KRT17 also contributes to delineate tumors falling into the squamous PDAC [111] (Figure 3) and to identify tumors that are chemoresistant to gemcitabine-and 5-FU-based regimens [112]. Hence, simplified PDAC stratification by assessment of expression profiles for a restricted number of proteins provides the opportunity to define clinically relevant molecular subtypes of PDAC in routine diagnostic laboratories, in both resectable [92,105,113] and advancedstage tumors [105] undergoing, e.g., volumetric whole-tumor analysis via radiomic-based investigations [113].…”