Wild-Type BRAF Is Required for Response to Panitumumab or Cetuximab in Metastatic Colorectal Cancer

Azienda Ospedaliera Niguarda Ca' Granda, Milano, Lombardy, Italy
Journal of Clinical Oncology (Impact Factor: 17.88). 11/2008; 26(35):5705-12. DOI: 10.1200/JCO.2008.18.0786
Source: PubMed

ABSTRACT PURPOSE Cetuximab or panitumumab are effective in 10% to 20% unselected metastatic colorectal cancer (CRC) patients. KRAS mutations account for approximately 30% to 40% patients who are not responsive. The serine-threonine kinase BRAF is the principal effector of KRAS. We hypothesized that, in KRAS wild-type patients, BRAF mutations could have a predictive/prognostic value. PATIENTS AND METHODS We retrospectively analyzed objective tumor responses, time to progression, overall survival (OS), and the mutational status of KRAS and BRAF in 113 tumors from cetuximab- or panitumumab-treated metastatic CRC patients. The effect of the BRAF V600E mutation on cetuximab or panitumumab response was also assessed using cellular models of CRC. Results KRAS mutations were present in 30% of the patients and were associated with resistance to cetuximab or panitumumab (P = .011). The BRAF V600E mutation was detected in 11 of 79 patients who had wild-type KRAS. None of the BRAF-mutated patients responded to treatment, whereas none of the responders carried BRAF mutations (P = .029). BRAF-mutated patients had significantly shorter progression-free survival (P = .011) and OS (P < .0001) than wild-type patients. In CRC cells, the introduction of BRAF V600E allele impaired the therapeutic effect of cetuximab or panitumumab. Treatment with the BRAF inhibitor sorafenib restored sensitivity to panitumumab or cetuximab of CRC cells carrying the V600E allele. CONCLUSION BRAF wild-type is required for response to panitumumab or cetuximab and could be used to select patients who are eligible for the treatment. Double-hit therapies aimed at simultaneous inhibition of epidermal growth factor receptor and BRAF warrant exploration in CRC patients carrying the V600E oncogenic mutation.

1 Follower
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The impact of KRAS signaling on cancerous inhibitor of protein phosphatase 2A (CIP2A) expression has not yet been explored. We investigated the impact of KRAS on CIP2A expression in colorectal cancer patients after colorectal liver metastasectomy. We examined CIP2A expression by immunohistochemistry (IHC) and used direct sequencing to identify the mutational status of KRAS exon 2 (codon 12 and 13). The association between CIP2A expression, KRAS genotype, clinicopathological parameters and survival were examined by the Kaplan-Meier method and the Cox proportional hazards model. A combination of immunoblotting and proliferation assays were employed to elucidate the role of CIP2A in signal transduction pathways in wild-type KRAS Caco-2 cells. A total of 220 colorectal cancer patients who had undergone colorectal liver metastasectomy were included in the study. The mutant KRAS genotype was associated with CIP2A overexpression. CIP2A expression was an independent prognostic marker in patients with wild-type KRAS metastatic colorectal cancer after colorectal liver metastasectomy (relative risk = 1.873, P = 0.019). Targeted silencing of CIP2A in Caco-2 cells (wild-type KRAS) led to decreased expression of pERK/ERK and decreased cell proliferation. Overexpression of mutant KRAS G12D in Caco-2 cells led to an increase in CIP2A expression and cell proliferation. In Caco-2 cells with the KRAS G12D, KRAS overexpression preserved the regulation effect of CIP2A in KRAS and abrogated the impact of CIP2A regulation on pERK/ERK and cell proliferation. CIP2A inhibition also increased the efficacy of cetuximab in Caco-2 cells. CIP2A is an independent prognostic marker in patients with wild-type KRAS metastatic colorectal cancer after colorectal liver metastasectomy.
    BMC Cancer 04/2015; 15(1):301. DOI:10.1186/s12885-015-1300-3 · 3.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of our study was to evaluate whether a panel of biomarkers, prospectively analysed might be able to predict patients' clinical outcome more accurately than RAS status alone. K-RAS (exons 2, 3, 4) wild type colorectal cancer patients, candidates to second/third-line cetuximab with chemotherapy were prospectively allocated into 2 groups on the basis of their profile: favourable (BRAF and PIK3CA exon 20 wild type, EGFR GCN ≥ 2.6, HER-3 Rajkumar score ≤ 8, IGF-1 immunostaining < 2) or unfavourable (any of the previous markers altered or mutated). After the introduction of N-RAS status (exons 2, 3, 4) only RAS wild type patients were considered eligible. Primary aim was response rate (RR). To detect a difference in terms of RR among patients with an unfavourable profile (estimated around 25%) and patients with a favourable profile (estimated around 60%), with a probability alpha of 0.05 and beta of 0.05, required sample size was 46 patients. Secondary endpoints were progression free survival (PFS) and overall survival (OS). Forty-six patients were enrolled. Seventeen patients (37%) were allocated to the favourable and 29 patients (63%) to the unfavourable profile. RR in the favourable and unfavourable group was 11/17 (65%) and 2/29 (7%) (p = 0.007) respectively. The favourable group also showed an improved PFS (8 months vs. 3 months, p < 0.0001) and OS (15 months vs. 6 months, p < 0.0001). Our results suggest that prospective selection of optimal candidates for cetuximab treatment is feasible and may be able to improve clinical outcome.
    Journal of Translational Medicine 05/2015; 13:140. DOI:10.1186/s12967-015-0501-5 · 3.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Activating mutations in the BRAF oncogene are found in 8-15% of colorectal cancer (CRC) patients and have been associated with poor survival. In contrast to BRAF mutant (MT) melanoma, inhibition of the MAPK pathway is ineffective in the majority of BRAFMT CRC patients. Therefore, identification of novel therapies for BRAFMT CRC is urgently needed. BRAFMT and WT CRC models were assessed in vitro and in vivo. Small molecule inhibitors of MEK1/2, MET and HDAC were employed, over-expression and siRNA approaches were applied, and cell death was assessed by flow cytometry, Western blotting, cell viability and caspase activity assays. Increased c-MET-STAT3 signalling was identified as a novel adaptive resistance mechanism to MEK inhibitors (MEKi) in BRAFMT CRC models in vitro and in vivo. Moreover, MEKi treatment resulted in acute increases in transcription of the endogenous caspase-8 inhibitor c-FLIPL in BRAFMT cells, but not in BRAFWT cells, and inhibition of STAT3 activity abrogated MEKi-induced c-FLIPL expression. In addition, treatment with c-FLIP-specific siRNA or HDAC inhibitors abrogated MEKi-induced upregulation of c-FLIPL expression and resulted in significant increases in MEKi-induced cell death in BRAFMT CRC cells. Notably, combined HDAC inhibitor/MEKi treatment resulted in dramatically attenuated tumor growth in BRAFMT xenografts. Our findings indicate that c-MET/STAT3-dependent upregulation of c-FLIPL expression is an important escape mechanism following MEKi treatment in BRAFMT CRC. Thus, combinations of MEKi with inhibitors of c-MET or c-FLIP (eg. HDAC inhibitors) could be potential novel treatment strategies for BRAFMT CRC. Copyright © 2015, American Association for Cancer Research.
    Clinical Cancer Research 03/2015; DOI:10.1158/1078-0432.CCR-14-2701 · 8.19 Impact Factor


Available from
May 21, 2014