Colorectal liver metastases (CRLMs) are the leading cause of cancer-related death in colorectal cancer; after curative resection of CRLMs, adjuvant chemotherapy is used to prevent recurrence. However, tumor recurrence after chemotherapy remains a significant therapeutic challenge. To investigate novel therapeutic targets for chemotherapy-resistant CRLM, we compared tissues from the same patients before and after chemotherapy using a phosphoproteomic approach.
Eighteen patients were treated with chemotherapy after resection of liver metastases and developed recurrent tumors during or after chemotherapy. TMT-based proteomic and phosphoproteomic analysis was performed on tumors and NATs obtained from patients and on 35 colorectal cancer cell lines (CRC35). Kinase activity profiles were obtained using PTM-SEA. A drug sensitivity-kinase activity correlation map was created using kinase activity data for CRC35 and drug sensitivity data from the publicly available small molecule sensitivity data set (CTD2).
Patients were divided into two groups: recurrence during adjuvant chemotherapy (During group: n=8) and recurrence after chemotherapy (After group: n=10). Overall survival was significantly shorter in the During group than in the After group. PAK1 activity was significantly upregulated in patients in During group. We then systematically selected PI3K inhibitors as drug candidates using Drug sensitivity-Kinase activity correlation map and confirmed anti-cancer effect in vitro and in vivo.
Our integrated analysis of pharmaco-phosphoproteomic data revealed PAK1 kinase activation associated with poor prognosis cases and PI3K kinase as a potential therapeutic target for chemotherapy resistance CRLM.