p21-Activated Kinase 4 (PAK4) as a Predictive Marker of Gemcitabine Sensitivity in Pancreatic Cancer Cell Lines

Abstract

Purposep21-activated kinases (PAKs) are involved in cytoskeletal reorganization, gene transcription, cell proliferation and survival, and oncogenic transformation. Therefore, we hypothesized that PAK expression levels could predict the sensitivity of pancreatic cancer cells to gemcitabine treatment, and PAKs could be therapeutic targets.Materials and MethodsCell viability inhibition by gemcitabine was evaluated in human pancreatic cancer cell lines (Capan-1, Capan-2, MIA PaCa-2, PANC-1, Aspc-1, SNU-213, and SNU-410). Protein expression and mRNA of molecules was detected by immunoblot analysis and reverse transcription polymerase chain reaction. To define the function of PAK4, PAK4 was controlled using PAK4 siRNA.ResultsCapan-2, PANC-1, and SNU-410 cells were resistant to gemcitabine treatment. Immunoblot analysis of signaling molecules reported to indicate gemcitabine sensitivity showed higher expression of PAK4 and lower expression of human equilibrative nucleoside transporter 1 (hENT1), a well-known predictive marker for gemcitabine activity, in the resistant cell lines. Knockdown of PAK4 using siRNA induced the upregulation of hENT1. In resistant cell lines (Capan-2, PANC-1, and SNU-410), knockdown of PAK4 by siRNA resulted in restoration of sensitivity to gemcitabine.ConclusionPAK4 could be a predictive marker of gemcitabine sensitivity and a potential therapeutic target to increase gemcitabine sensitivity in pancreatic cancer.

Prognostic value of p21‐activated kinase 4 in resected pancreatic cancer

“…Similarly, hyperactivity of PAK4 has been noted in other types of cancer . Moreover, we reported previously that hENT1 could be regulated with PAK4 expression, which is a predictive marker of gemcitabine sensitivity .…”

“…Another unexpected finding was the positive correlation between PAK4 and hENT1 expression status in our human pancreatic cancers, as we had previously demonstrated an inverse correlation between the two proteins and that knockdown of PAK4 was associated with up‐regulated hENT1 . This may partly be ascribed to the differences in the antibodies used for hENT1; in the previous study, the anti‐SLC29A1 rabbit polyclonal antibody was used, whereas the rabbit monoclonal SP120 antibody (which has been recently developed for in vitro diagnostics use) was used for the current study.…”

“…We have recently demonstrated higher PAK4 expression in gemcitabine‐resistant pancreatic cancer cell lines, and that PAK4 knockdown in these cell lines by siRNA induced the up‐regulation of hENT1 and increased sensitivity to gemcitabine . In order to further explore the expression status of PAK4 – in addition to PAK1, TS, and hENT1 – in human pancreatic cancer tissues, we performed an immunohistochemical analysis of these four markers on tissue microarrays constructed from 160 surgically resected pancreatic adenocarcinomas.…”

PAK4 Pathway as a Potential Therapeutic Target in Pancreatic Cancer

“…KPT-9274 is currently being trialled in an early-phase study (NCT02702492). Furthermore, studies combining PAK4 depletion with traditional chemotherapy have also been encouraging [20]. Three PDAC lines that were resistant to gemcitabine demonstrated reduced cell viability when used in combination with transient PAK4 siRNA, suggesting PAK4 inhibition could be used as in combination with chemotherapy.…”

Structure, biochemistry, and biology of PAK kinases

“…For example, overexpression of PAK1 confers chemo-resistance to PI-3K inhibitors in colon cancer (Qing et al, 2012) and B-cell lymphomas (Walsh et al, 2013), and resistance to MET inhibitors in pancreatic cancer cells (Zhou et al, 2014). Similar to PAK1, upregulation of PAK4 promotes insensitivity to chemotherapies such as doxorubicin or paclitaxel (Park et al, 2013), cisplatin (Shu et al, 2015; Fu et al, 2014) in different cancer types, and gemcitabine in cancer cells (Moon et al, 2015). Likewise, PAK5 overexpression confers resistance to paclitaxel (Li et al, 2013) and cisplatin in cancer cells (He et al, 2014; Zhang et al, 2015).…”