SMAD4 Loss Is Associated with Cetuximab Resistance and Induction of MAPK/JNK Activation in Head and Neck Cancer Cells

Abstract

Purpose We previously demonstrated an association between decreased SMAD4 expression and cetuximab resistance in head and neck squamous cell carcinoma (HNSCC). The purpose of this study was to further elucidate the clinical relevance of SMAD4 loss in HNSCC. Experimental Design SMAD4 expression was assessed by immunohistochemistry in 130 newly diagnosed and 43 recurrent HNSCC patients. Correlative statistical analysis with clinicopathological data was also performed. OncoFinder, a bioinformatics tool, was used to analyze molecular signaling in TCGA tumors with low or high SMAD4 mRNA levels. The role of SMAD4 was investigated by shRNA knockdown and gene reconstitution of HPV-negative HNSCC cell lines in vitro and in vivo. Results Our analysis revealed that SMAD4 loss was associated with an aggressive, HPV-negative, cetuximab-resistant phenotype. We found a signature of pro-survival and anti-apoptotic pathways that were commonly dysregulated in SMAD4-low cases derived from TCGA-HNSCC dataset and an independent oral cavity squamous cell carcinoma (OSCC) cohort obtained from GEO. We show that SMAD4 depletion in a HNSCC cell line induces cetuximab resistance and results in worse survival in an orthotopic mouse model in vivo. We implicate JNK and MAPK activation as mediators of cetuximab resistance and provide the foundation for the concomitant EGFR and JNK/MAPK inhibition as a potential strategy for overcoming cetuximab resistance in HNSCCs with SMAD4 loss. Conclusions Our study demonstrates that loss of SMAD4 expression is a signature characterizing the cetuximab-resistant phenotype and suggests that SMAD4 expression may be a determinant of sensitivity/resistance to EGFR/MAPK or EGFR/JNK inhibition in HPV-negative HNSCC tumors.

The fidelity of cancer cells in PDX models: Characteristics, mechanism and clinical significance

“…A recent study in head and neck squamous cell carcinoma showed genomic SMAD family member 4 (SMAD4) alterations in PDX . Surprisingly, SMAD4 loss has been shown to negatively correlate with cetuximab sensitivity, which is not in agreement with the conclusions of previous studies . These results further raise the possibility that the effects of genomic alterations upon drug responses in PDXs can vary.…”

Targeting MAPK Signaling in Cancer: Mechanisms of Drug Resistance and Sensitivity

“…In the same vein, JNK also can modulate resistance to 5-fluorouracil (5-FU) in CRC by enhancing BCL2 phosphorylation and autophagy, which protect against 5-FU induced apoptosis [85]. Such modulatory effects of JNK on responses to chemotherapies and targeted therapies were also observed in gastric cancer [86], hepatocellular carcinoma [87], head and neck cancer [88], endometrial cancer [89], and ovarian cancer [90]. An interesting finding in this context is that JNK signaling seems specifically important for the maintenance of cancer stem cells in different cancer types including pancreatic [91], endometrial [92], and ovarian cancer [93].…”

Rational combination with PDK1 inhibition overcomes cetuximab resistance in head and neck squamous cell carcinoma

“…Cetuximab, an EGFR-blocking antibody, is currently the only approved EGFR-targeting therapy for patients with metastatic HNSCC (6,7). The efficacy of cetuximab is limited by intrinsic and acquired drug resistance, which is due mainly to tumor heterogeneity and genetic instability; these lead to constitutive activation of EGFR downstream signaling pathways and functional redundancy or compensatory activation of alternative growth factor receptor pathways (8)(9)(10)(11)(12)(13)(14). The current response rate to cetuximab as a single agent in HNSCC is only approximately 13% (15).…”