Background: Src is a nonreceptor tyrosine kinase involved in the crosstalk and mediation of many signaling pathways that promote cell proliferation, invasion and angiogenesis. Elevation of Src activity has been reported in many types of cancers including gastric cancer (GC) and biliary tract cancer (BTC). The purpose of this study is to evaluate Src as a therapeutic target and to elaborate the biomarkers of Src inhibitor in GC and BTC.

Methods: Ten gastric cancer cell lines (SNU-1, 5, 16, 216, 601, 620, 638, 668, 719, NCI-N87) and 8 biliary tract cancer cell lines (SNU-245, 308, 478, 869, 1079, 1196, HuCCT1, TFK1) were used. Saracatinib and bosutinib were used as Src inhibitors. MTT assay, colony formation assay and 3D culture were done for determining growth inhibitory effect of Src inhibitors, alone or in combination with chemotherapeutic agents (5-FU, gemcitabine, cisplatin). Cell cycle analysis was done by FACS Calibur flow cytometer. Matrigel invasion assay and wound healing assay were done. The methods described by Chou and Talalay were used to determine whether a synergistic effect existed between drug combination. Tumor xenograft model was made and used for in vivo test of Src inhibitors.

Results: Among 10 GC cells, SNU216 and NCI-N87 were sensitive to Src inhibitor. These sensitive cells showed high levels of pSRC(Y416) and pFAK (Y861, Y397, Y925). These 2 sensitive GC cells are both HER2 amplified cells. However, HER2-positive breast cancer (BC) cells (SKBR3, BT474, MDA-MB453) were resistant to Src inhibitor. Contrast to these resistant BC cells, SNU216 and N87 showed high expression of integrin αV, β4 and β8. Especially, in case of integrin β8, the mRNA/protein levels were highest in SNU216 and N87 among all GC cells. Src inhibitor-sensitive GC cells showed the apoptosis by Src inhibitor and synergism with 5-FU in vitro and in vivo.

Among 8 BTC cells, 3 cells were sensitive to Src inhibitor (SNU308, SNU478 and HuCCT1) in terms of growth inhibition and migration/invasion inhibition. Sensitive cells showed high levels of integrin α2, α3 and β4. Src inhibitor induced G1 arrest and decreased pSrc, pFAK, and pERK in sensitive cells. Inhibition of pSrc was accompanied with increase of PTEN and decrease of pAKT. Src inhibitor showed the synergistic effects with cytotoxic chemotherapeutic agents (gemcitabine and cisplatin) in vitro and in vivo. When the Src was inhibited, pSTAT3 was increased thru increase of IL-6 in some cells.

Conclusion: Taken together, Src could be a potential therapeutic target in gastric cancer and biliary tract cancer. The role of integrin as a biomarker for Src inhibitor should be further investigated.

Citation Format: Ah-Rong Nam, Hyun-Jin Nam, Kyo Hwa Kang, Ji Eun Park, Tae Yong Kim, Sae-Won Han, Sang-Hyun Song, Seock-Ah Im, Tae-You Kim, Do-Youn Oh, Yung-Jue Bang. Evaluation of Src as a therapeutic target and development of biomarkers of Src inhibitor in cancer. [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 747. doi:10.1158/1538-7445.AM2014-747