Abstract 3087: Cancer-associated fibroblasts promote resistance to chemotherapy through the p53/ERK1/2/DKK1 pathway

Abstract Introduction: Chemotherapy constitutes the cornerstone of adjuvant therapy for colorectal cancer (CRC); however, acquired resistance issues can lead to a decrease in the efficiency of chemotherapy. Dickkopf-1 (DKK1) promotes MDSC infiltration, immunosuppression, and cancer relapse. Cancer-associated fibroblasts (CAFs) play a pivotal role in the tumor microenvironment. The purpose of this study was to examine whether CAFs play a critical role in acquired chemotherapy resistance. Methods: CAFs were treated with either 5-FU, oxaliplatin or sn38 in a time- and dose-dependent manner. Expression of DKK1, p53, fibroblast activation protein (FAP), and phosphorylated ERK1/2, JNK, p38 were determined by either RNA-seq, western blot, real-time (RT)-PCR, ELISA, or immunofluorescence (IF) staining. To determine whether targeting DKK1 would enhance the efficacy of 5-FU treatment, APCf/f; CDX2-Cre/ERT2 mice were injected with tamoxifen to induce adenoma formation followed by treatment with 5-FU in combination with administration of either normal IgG or anti-DKK1 antibody. Tumor tissues were harvested and flow cytometric analyses performed. Results: Treatment of CAFs with either 5-FU, oxaliplatin, or sn38 (an active metabolite of irinotecan) increased DKK1 expression and secretion, suggesting a general induction of DKK1 by chemotherapeutic agents. Treatment with these agents resulted in the activation of MAPK as noted by the increased phosphorylation of ERK1/2, JNK, and p38. Inhibition or knockdown of MEK/ERK1/2, but not JNK and p38, blocked the induction of DKK1 expression, suggesting that chemotherapy increased DKK1 expression through activation of ERK1/2 signaling pathway in CAFs. Consistently, elevated levels of phospho-ERK were found in CAFs in surgically resected samples from patients treated with neo-adjuvant therapy prior to surgery compared to non-chemotherapy controls as determined by double IF staining for phospho-ERK1/2 and FAP. Chemotherapeutic agents induce DNA damage-related upregulation of p53 in CAFs. Knockdown of p53 blocked increased ERK1/2 phosphorylation and DKK1 expression after treatment with the chemotherapeutic agents. These results suggested that chemotherapeutic agents increased DKK1 expression through p53-dependent activation of ERK1/2. Treatment with 5-FU increased levels of DKK1 in plasma, and coincidently, increased myeloid-derived suppressor cell (MDSC) tumor infiltration as determined by FACS analysis; these increases were blocked by treatment with anti-DKK1 neutralizing antibody. Moreover, anti-DKK1 antibody enhanced the antitumor efficacy of 5-FU as noted by the significantly decreased tumor size and numbers. Conclusions: Our current study identified a novel mechanism contributing to chemotherapy resistance. Importantly, our findings provide evidence for targeting ERK1/2/DKK1 to counteract chemotherapy resistance for CRC treatment. Citation Format: Zhijie Yin, Yuning Zhou, Xudong Zhu, Chi Wang, Heidi L. Weiss,B. Mark Evers, Qingding Wang. Cancer-associated fibroblasts promote resistance to chemotherapy through the p53/ERK1/2/DKK1 pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3087.