Sorafenib combined vitamin K induces apoptosis in human pancreatic cancer cell lines through RAF/MEK/ERK and c-Jun NH2-terminal kinase pathways

Abstract

Apoptosis has been shown to be induced by many agents, including the clinically useful Sorafenib and K vitamins (VKs). Since few agents have activity against pancreas cancer cell growth, we evaluated the role of naturally occurring K vitamins and Sorafenib both independently and together on the growth in culture of pancreas adenocarcinoma cell lines, including PL-5, PANC-1, and MIA PaCa-2. We found that when a K vitamin was combined with Sorafenib, the dose of Sorafenib required for growth inhibition was substantially reduced. Furthermore, growth could be inhibited at doses of each VK plus Sorafenib in combination that were ineffective when used alone. This effect was seen using vitamins K1, K2, and K5. The combination of VK1 plus Sorafenib-induced apoptosis, as determined by both FACS and TUNEL staining. Phospho-ERK and Bcl-2 levels were decreased, but not levels of other bcl-2 family members. Cleavage of caspases 3 and 8, PARP and Bid were all induced by this combination. Vitamin K1 plus Sorafenib combination also resulted in elevated levels of activated c-Jun N-terminal kinase (JNK) and its substrates c-Jun and FasL. JNK inhibition partly antagonized the induction of apoptosis. Thus, combination VK1 plus Sorafenib strongly induced growth inhibition and apoptosis in pancreas cancer cells, involving both inhibition of the RAF/MEK/ERK pathway as well as activation of the JNK, c-Jun and FasL apoptotic pathway. Since both agents are available for human use, the combination is attractive for evaluation against pancreas cancer growth in vivo.