Colon cancers carrying BRAF V600E and β-catenin T41A activating mutations are resistant to numerous common anticancer drugs

Abstract

Abstract. Colorectal cancer is a common malignancy with a high prevalence and associated mortality rate. However, the preclinical tools currently used for drug development are insufficient. The aim of the present study was to establish and characterize a specific patient-derived colon cancer xenograft (PDCCX) mouse model for drug testing. Primary colon tumors were obtained from 10 patients by surgical resection, and tumor tissues were subsequently grafted into nude mice followed by consecutive passages. Primary tumors and xenograft tumors were collected and processed for DNA sequencing, histological evaluation and immunohistochemical staining. The responses of fifth-generation PDCCX mice to 5-fluorouracil, oxaliplatin, and cetuximab were assessed. Two PDCCX cell lines were successfully established. The histology and protein expression levels of SMAD family member 3, epidermal growth factor receptor, c-MET, caudal type homeobox 2, E-cadherin and β-catenin in the xenograft tumors were consistently maintained from the primary cancer tissues. BRAF V600E and β-catenin T41A double mutations were identified in one cell line, and were associated with a lack of response to 5-fluorouracil, oxaliplatin and cetuximab treatment. This PDCCX cell line may provide a reliable tool for preclinical evaluation of the efficacy of novel therapies that may target the BRAF V600E and β-catenin mutations.

Identification of AKT1/β-catenin mutations conferring cetuximab and chemotherapeutic drug resistance in colorectal cancer treatment

“…Similarly, in the present study, the cytotoxicity of cetuximab was lower in CTNNB1 T41A, S45F and S33P mutant Caco-2 cells compared with the WT cells at all dosage levels. The results of Xu et al (35) strongly support the present results; however, the study could not reveal the individual effect of the CTNNB1 T41A mutation on cetuximab because the mice also had a BRAF mutation along with the CTNNB1 T41A mutation. On the other hand, the effects of S45F and S33P mutations on cetuximab resistance have not been studied before, to the best of our knowledge.…”

“…Cetuximab is a monoclonal antibody that specifically inhibits EGFR and has been used as a biological agent in CRC treatment (5) (14,(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37). Furthermore, the AKT1 E49K mutation has been observed in patients with bladder cancer (38), but not in patients with CRC.…”

“…Genetic mutations in GSK-3β phosphorylation sites (S33, S37, S45 or T41) of β-catenin are known to inhibit proteasomal degradation of β-catenin coding by CTNNB1 (39). There is only one study demonstrating the association of CTNNB1 T41A mutation with cetuximab resistance (35), in which cetuximab did not inhibit tumor growth in xenograft mice carrying both CTNNB1 T41A and BRAF V600E mutations. Similarly, in the present study, the cytotoxicity of cetuximab was lower in CTNNB1 T41A, S45F and S33P mutant Caco-2 cells compared with the WT cells at all dosage levels.…”

“…There is still a need for further research as the studies are inconsistent, and there are no in vivo studies supporting in vitro results that will allow these findings to be used in treatment. Although Xu et al (35) showed that oxaliplatin and 5-FU do not inhibit tumor growth in xenograft mice carrying both CTNNB1 T41A and BRAF V600E mutations, the effects of CTNNB1 S45F and S33P mutations on oxaliplatin and 5-FU resistance have not been studied before. Furthermore, there is no study showing the contribution of AKT1 E17K, E49K and L52R mutations to resistance to oxaliplatin, irinotecan and 5-FU, to the best of our knowledge.…”

Destruxin B Suppresses Drug-Resistant Colon Tumorigenesis and Stemness Is Associated with the Upregulation of miR-214 and Downregulation of mTOR/β-Catenin Pathway

“…In another experiment, we showed that a single DB pre-treatment (below IC50) could significantly reduce the tumor-initiating ability of IGF1-cultured DLD-1 colon CSC-like cells in vivo. Mechanistically, DB treatment was associated with the decreased expression of a key CSC marker, β-catenin, which has been shown to be aberrantly increased in malignant colon cancer cells and associated with the generation of drug-resistance [ 36 , 37 ]. DB-mediated suppression of β-catenin was also accompanied with an increased miR-214 level, which has a potential binding site at β-catenin’s 3′UTR.…”