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Background: Recent evidence has highlighted the role of hepatocyte growth factor (HGF) as a putative biomarker to predict EGFR inhibitor resistance. This study investigated the impact of plasma HGF levels on EGFR inhibition and the therapeutic implications of MET inhibition in KRAS, NRAS, and BRAF (RAS/RAF) wild-type colorectal cancer (CRC). Methods: Clinical outcomes were analyzed according to the plasma HGF levels in patients with metastatic CRC (mCRC) receiving palliative first-line cetuximab or bevacizumab + FOLFIRI chemotherapy. Then, in vitro experiments were conducted to validate the clinical findings and to establish pre-clinical evidence of MET inhibition in the HGF-high population. Results: From March 2015 to September 2019, a total of 80 patients were enrolled. The median age was 63 (range, 24-85) years. Of these, 45 patients (56.2%) were treated with bevacizumab + FOLFIRI and 35 patients (43.8%) were treated with cetuximab + FOLFIRI. Among patients with evaluable disease (43 patients (95.6%) in the bevacizumab group and 34 patients (97.1%) in the cetuximab group), the objective response rate was 60.0% and 37.8%, respectively (p=0.162). The median serum HGF level was 374.75 (range, 9.43-30,644.44) pg/mL, and the optimal cut-off value of HGF levels was 12.70 pg/mL by the maximal chi-square method. During a median follow-up of 29.3 (range, 1.2-71.3) months, both progression-free survival (PFS) and overall survival (OS) were significantly shorter in the high HGF group compared with the low HGF group: median 11.8 (95% confidence interval [CI], 10.5-13.1) months vs. 24.7 (95% CI, 23.4-25.9) months for PFS (p=0.009), and median 21.1 (95% CI, 17.9-24.3) months vs. not reached for OS (p=0.018). The difference in PFS and OS was statistically significant in the cetuximab group (p=0.003 for PFS and p=0.035 for OS), but not in the bevacizumab group. In five RAS/RAF wild-type CRC cell lines (Caco-2, COLO 320DM, KM12C, SNU-C1, and SNU-C4), the addition of HGF activated ERK1/2 and AKT via MET phosphorylation. In the cytotoxicity assays, Caco-2 and SNU-C4 were relatively sensitive to cetuximab compared with the others and, in the presence of HGF, cetuximab sensitivity was significantly decreased in the two cells. Moreover, capmatinib, a MET inhibitor, abrogated the effect of HGF on common downstream signaling pathways of EGFR and MET and thus the cetuximab resistance was significantly overcome in vitro. Conclusions: Among patients with mCRC receiving cetuximab + FOLFIRI, those with high plasma HGF levels had significantly worse PFS and OS. HGF induced cetuximab resistance by AKT and ERK activation while capmatinib, a MET inhibitor, significantly increased the anti-tumor effects of cetuximab in the presence of HGF in vitro. Our data may provide evidence of future clinical trials of dual EGFR and MET targeting strategies in patients with HGF-high, RAS/RAF wild-type mCRC. Citation Format: Sang-A Kim, Hyejoo Park, Kui-Jin Kim, Ji-Won Kim, Ji Hea Sung, Milang Nam, Ju Hyun Lee, Eun Hee Jung, Koung Jin Suh, Ji Yun Lee, Se Hyun Kim, Jeong-Ok Lee, Jin Won Kim, Yu Jung Kim, Jee Hyun Kim, Soo-Mee Bang, Jong Seok Lee, Keun-Wook Lee. Cetuximab resistance induced by hepatocyte growth factor is overcome by MET inhibition in KRAS, NRAS, and BRAF wild-type colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5138.

Background: PIK3CA, encoding p110α subunit of PI3K, is the third most frequently mutated gene in gastric cancer (GC): 9–13% of non-hypermutated tumors and 32% of hypermutated tumors. Thus, PI3K pathway could be a potential therapeutic target in GC. Nevertheless, only few studies have been conducted so far. Materials and Methods: This preclinical study aimed to investigate the anti-tumor effects of alpelisib (Novartis, Basel, Switzerland), a PI3K p110α-specific inhibitor, using in vitro and in vivo models of GC. The combinatorial effects of alpelisib and paclitaxel, a commonly used agent for GC, were also evaluated. Results: Among eight GC cell lines (SNU1, SNU16, SNU484, SNU601, SNU638, SNU668, AGS, and MKN1), three harbored PIK3CA hotspot mutations: E542K in SNU601, E545A and E453K in AGS, and E545K in MKN1, while the others were PIK3CA wild-type. These three PIK3CA mutant cells were predominantly sensitive to alpelisib. Alpelisib monotherapy decreased AKT and S6K1 phosphorylation and induced G0/G1 cell cycle arrest regardless of PIK3CA mutational status. Moreover, in PIK3CA mutant cells, GSK3β and BAD phosphorylation was potently abrogated by alpelisib alone, which was not evident in PIK3CA wild-type cells. Alpelisib in combination with paclitaxel demonstrated synergistic anti-proliferative effects, preferentially in PIK3CA mutant cells, by increasing caspase 3/7 activity and resulting in increased apoptosis. Moreover, the alpelisib and paclitaxel combination more potently inhibited the cell migration in wound healing assays and the expression of epithelial-mesenchymal transition (EMT)-associated proteins including Snail and Twist in PIK3CA mutant cells, compared with PIK3CA wild-type cells. In a mouse xenograft model of MKN1 cells, alpelisib combined with paclitaxel significantly enhanced the anti-tumor activity by decreasing Ki-67 expression and increasing TUNEL expression. Moreover, this combination tended to prolong survival of tumor-bearing mice for 4 weeks of treatment period without resulting in significant change in body weight. Conclusions: Alpelisib alone or in combination with paclitaxel demonstrated promising anti-tumor activity and tolerability in in vitro and in vivo models of PIK3CA mutant GC via inactivating PI3K down-stream molecules, decreasing cell migration, and increasing apoptosis. Our data suggest that this novel combination is worthy of further clinical investigations in patients with PIK3CA mutant GC. Keywords: alpelisib; BYL719; paclitaxel; PIK3CA; gastric cancer; combination; chemotherapy Citation Format: Ji-Won Kim, Kui-Jin Kim, Ji Hea Sung, Koung Jin Suh, Ji Yun Lee, Se Hyun Kim, Jin Won Kim, Jeong-Ok Lee, Yu Jung Kim, Soo-Mee Bang, Jee Hyun Kim, Jong Seok Lee, Keun-Wook Lee. Preclinical study of antitumor effect of alpelisib combined with paclitaxel in gastric caner [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C074. doi:10.1158/1535-7163.TARG-19-C074

Background: Agents targeting HER2 or EGFR have been applied in several cancer types. Tumor microenvironment including tumor-infiltrating lymphocytes could be a predictive marker in HER2- or EGFR- targeted therapy, although there are some controversies. However, the effects of HER2 and EGFR inhibition on tumor microenvironment are unclear. Method: We screened HER2, EGFR, and PD-L1 expression in gastric cancer cell lines by western blot (SNU216, SNU668, SNU719, AGS, N87, YCC3, and YCC10). HER2 and EGFR was inhibited by using dual inhibitor (afatinib, lapatinib). After HER2 and EGFR inhibition, the change of PD-L1 expression was evaluated in HER2 overexpressed cell lines (SNU216, N87, SKBR3) at western blot, FACS, PCR, and qPCR. Selective blockade for down-steam molecules of HER2 and EGFR was conducted by using pictilisib (PI3K inhibitor) and trametinib (MEK inhibitor). The change of chemokines such as CXCL1, CCL2, and CCL21 was evaluated after HER2 and EGFR inhibition by PCR. In clinical data, PD-L1 expression and HER2 expression in resected gastric cancer were also evaluated by immunohistochemistry analysis. Results: EGFR-overexpressed or HER2-overexpressed gastric cancer cell lines (SNU216, SNU668, N87) showed higher protein expression of PD-L1. PD-L1 expression decreased with dose-dependent manner in afatinib- or lapatinib- treated cell lines (SNU216, N87, SKBR3). In pictilisib-treated cell lines, PD-L1 was also down-regulated. However, trametinib-treated cell lines did not show down-regulation of PD-L1. After lapatinib treatment in HER2 overexpressed cell lines, CXCL1, CCL21, and CCL2 decreased with dose-dependent manner. In 289 patients with resected gastric cancer, there was a significant association between HER2 and PD-L1 expression (p = 0.03). Conclusions: PD-L1 is associated with HER2 and EGFR expression. PD-L1 is regulated by inhibition of PI3K pathway. Therefore, HER2 or EGFR inhibition could interact with tumor microenvironment by down-regulation of expression of PD-L1 and chemokines. Citation Format: Jin Won Kim, Ji Hea Sung, Mi Hyun Kang, Ji-Won Kim, Se-Hyun Kim, Keun-Wook Lee, Hye Seung Lee, Jee Hyun Kim. HER2 or EGFR inhibition interacts with tumor microenvironment by downregulation of PD-L1 and chemokines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5136.

Pancreatic cancer is a highly lethal disease. Although gemcitabine is activelyused in pancreatic cancer, modest activity and relativeresistanceare revealed.P21-activated kinases(PAKs) are involved in cytoskeletal reorganization, gene transcription, cellproliferation and survival, and oncogenic transformation.The gene amplification and protein overexpression of PAK1 and PAK4were reported in pancreatic cancer, which were associated with K-ras mutation, MUC13 and Smad4. Therefore, we hypothesized that PAKs could predict the drug-sensitivity of gemcitabine in pancreatic cancer and could be a therapeutic target. Using cell viability assay of human pancreatic cancer cell lines (Capan1, Capan2, MIA-paca2, PANC1, Aspc1, SNU213, SNU410) for gemcitabine, Capan-2, PANC-1 and SNU-410 cell lines was identifiedas resistant cell lines for gemcitabine. Through western blots of molecules related with down-steam pathway and drug-sensitivity, higher expression of PAK4 and lower expression of human equilibrative nucleoside transporter 1 (hENT1) were associated with the resistance for gemcitabine. PAK4 down-regulation through siRNA induced the up-regulation of hENT1, which is well-known as predictive marker for gemcitabine activity. In resistance cell lines (Capan-2, PANC-1, SNU-410), down-regulation of PAK4 through siRNArestored the drug-sensitivity for gemcitabine. In conclusion, PAK4 can be a potential predictive marker and therapeutic target in gemcitabine chemotherapy for pancreatic cancer. Citation Format: Sung Ung Moon, Jin Won Kim, Ji Hea Sung, Mi Hyun Kang, Hyun Chang, Jeong Ok Lee, Yu Jung Kim, Keun Wook Lee, Jee Hyun Kim, Soo Mee Bang, Jong Seok Lee. P21-activated kinase 4 (PAK4) as a predictive marker for gemcitabine in pancreatic cancer cell line. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 912. doi:10.1158/1538-7445.AM2014-912