A MEK/PI3K/HDAC inhibitor combination therapy for KRAS mutant pancreatic cancer cells

// Irene Ischenko 1 , Oleksi Petrenko 1 and Michael J. Hayman 1 1 Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY, USA Correspondence to: Oleksi Petrenko, email: // Michael J. Hayman, email: // Keywords : PDAC, KRAS, MYC, MEK, PI3K Received : May 13, 2015 Accepted : June 14, 2015 Published : June 19, 2015 Abstract Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive, metastatic disease with limited treatment options. Factors contributing to the metastatic predisposition and therapy resistance in pancreatic cancer are not well understood. Here, we used a mouse model of KRAS-driven pancreatic carcinogenesis to define distinct subtypes of PDAC metastasis: epithelial, mesenchymal and quasi-mesenchymal. We examined pro-survival signals in these cells and the therapeutic response differences between them. Our data indicate that the initiation and maintenance of the transformed state are separable, and that KRAS dependency is not a fundamental constant of KRAS-initiated tumors. Moreover, some cancer cells can shuttle between the KRAS dependent (drug-sensitive) and independent (drug-tolerant) states and thus escape extinction. We further demonstrate that inhibition of KRAS signaling alone via co-targeting the MAPK and PI3K pathways fails to induce extensive tumor cell death and, therefore, has limited efficacy against PDAC. However, the addition of histone deacetylase (HDAC) inhibitors greatly improves outcomes, reduces the self-renewal of cancer cells, and blocks cancer metastasis in vivo. Our results suggest that targeting HDACs in combination with KRAS or its effector pathways provides an effective strategy for the treatment of PDAC.