Clinical and Genomic Features of HER2 Exon 20 Insertion Mutations and Characterization of HER2 Expression by Immunohistochemistry in East Asian Non-Small-Cell Lung Cancer.

PURPOSE: HER2-altered non-small-cell lung cancer (NSCLC) represents a diverse subgroup, including mutations, amplifications, and overexpression. However, HER2 exon 20 insertion mutations are emerging as a distinct molecular subtype with expanding therapeutic options. We describe the molecular epidemiology and genomic features of HER2-altered NSCLC in an Asian tertiary cancer center. METHODS: We identified patients with HER2-mutated NSCLC in our institutional database, collating clinicopathological features and treatment outcomes. The genomic landscape of human epidermal growth factor receptor 2 (HER2)-mutated NSCLC was further evaluated using whole-exome sequencing (WES) data from combined local and publicly available data sets. HER2 amplification and overexpression as selection biomarkers in NSCLC were further interrogated using HER2 immunohistochemistry and correlations with WES and RNA sequencing data. RESULTS: Among 1,252 patients with consecutive lung adenocarcinoma undergoing routine next-generation sequencing, the prevalence of HER2 mutations was 3.1%-exon 20 insertion mutations comprised 2.7%. We examined the clinicopathological features in 55 patients with HER2-mutated NSCLC comprising 40 exon 20 insertion and 15 nonexon 20 insertion mutations. The most common exon 20 insertion mutation was HER2Y772_A775dup in 30 (75%), followed by HER2G776delinsVC in five patients (13%). There were limited responses to HER2-directed therapies apart from trastuzumab-deruxtecan, and no responses were seen with immunotherapy monotherapy. Evaluating the genomics features of HER2 exon 20 insertion mutations using WES data revealed low tumor mutational burden (TMB), low incidence of cancer driver comutations, and a predominance of aging mutational signature-similar to EGFR-mutated tumors. In contrast, uncommon (or nonexon 20 insertion) HER2-mutated tumors resembled EGFR wild-type tumors with higher TMB, higher frequency of cancer driver comutations, and greater presence of smoking and APOBEC mutational signature. Finally, in evaluating HER2 immunohistochemistry in all lung adenocarcinoma, there was significant discordance comparing different scoring systems and poor correlation with HER2 RNA expression and HER2 amplification. CONCLUSION: The incidence of HER2 mutations is 3.1% in East Asian nonsquamous NSCLC. HER2 exon 20 insertion-mutated tumors appear genomically distinct from uncommon (nonexon 20 insertion) HER2 mutations, the latter demonstrating higher TMB, co-occurring drivers, and predominant nonaging mutational signature. The therapeutic implications of the genomic and clinical features of HER2-mutated NSCLC warrant further investigation.

Clonal MET Amplification as a Determinant of Tyrosine Kinase Inhibitor Resistance in Epidermal Growth Factor Receptor-Mutant Non-Small-Cell Lung Cancer.

PURPOSE: Mesenchymal epithelial transition factor ( MET) activation has been implicated as an oncogenic driver in epidermal growth factor receptor ( EGFR)-mutant non-small-cell lung cancer (NSCLC) and can mediate primary and secondary resistance to EGFR tyrosine kinase inhibitors (TKI). High copy number thresholds have been suggested to enrich for response to MET inhibitors. We examined the clinical relevance of MET copy number gain (CNG) in the setting of treatment-naive metastatic EGFR-mutant-positive NSCLC. PATIENTS AND METHODS: MET fluorescence in situ hybridization was performed in 200 consecutive patients identified as metastatic treatment-naïve EGFR-mutant-positive. We defined MET-high as CNG greater than or equal to 5, with an additional criterion of MET/centromeric portion of chromosome 7 ratiο greater than or equal to 2 for amplification. Time-to-treatment failure (TTF) to EGFR TKI in patients identified as MET-high and -low was estimated by Kaplan-Meier method and compared using log-rank test. Multiregion single-nucleotide polymorphism array analysis was performed on 13 early-stage resected EGFR-mutant-positive NSCLC across 59 sectors to investigate intratumoral heterogeneity of MET CNG. RESULTS: Fifty-two (26%) of 200 patients in the metastatic cohort were MET-high at diagnosis; 46 (23%) had polysomy and six (3%) had amplification. Median TTF was 12.2 months (95% CI, 5.7 to 22.6 months) versus 13.1 months (95% CI, 10.6 to 15.0 months) for MET-high and -low, respectively ( P = .566), with no significant difference in response rate regardless of copy number thresholds. Loss of MET was observed in three of six patients identified as MET-high who underwent postprogression biopsies, which is consistent with marked intratumoral heterogeneity in MET CNG observed in early-stage tumors. Suboptimal response (TTF, 1.0 to 6.4 months) to EGFR TKI was observed in patients with coexisting MET amplification (five [3.2%] of 154). CONCLUSION: Although up to 26% of TKI-naïve EGFR-mutant-positive NSCLC harbor high MET CNG by fluorescence in situ hybridization, this did not significantly affect response to TKI, except in patients identified as MET-amplified. Our data underscore the limitations of adopting arbitrary copy number thresholds and the need for cross-assay validation to define therapeutically tractable MET pathway dysregulation in EGFR-mutant-positive NSCLC.

Long noncoding RNA EGFR-AS1 mediates epidermal growth factor receptor addiction and modulates treatment response in squamous cell carcinoma.

Targeting EGFR is a validated approach in the treatment of squamous-cell cancers (SCCs), although there are no established biomarkers for predicting response. We have identified a synonymous mutation in EGFR, c.2361G>A (encoding p.Gln787Gln), in two patients with head and neck SCC (HNSCC) who were exceptional responders to gefitinib, and we showed in patient-derived cultures that the A/A genotype was associated with greater sensitivity to tyrosine kinase inhibitors (TKIs) as compared to the G/A and G/G genotypes. Remarkably, single-copy G>A nucleotide editing in isogenic models conferred a 70-fold increase in sensitivity due to decreased stability of the EGFR-AS1 long noncoding RNA (lncRNA). In the appropriate context, sensitivity could be recapitulated through EGFR-AS1 knockdown in vitro and in vivo, whereas overexpression was sufficient to induce resistance to TKIs. Reduced EGFR-AS1 levels shifted splicing toward EGFR isoform D, leading to ligand-mediated pathway activation. In co-clinical trials involving patients and patient-derived xenograft (PDX) models, tumor shrinkage was most pronounced in the context of the A/A genotype for EGFR-Q787Q, low expression of EGFR-AS1 and high expression of EGFR isoform D. Our study reveals how a 'silent' mutation influences the levels of a lncRNA, resulting in noncanonical EGFR addiction, and delineates a new predictive biomarker suite for response to EGFR TKIs.

Tongue carcinoma infrequently harbor common actionable genetic alterations.

BACKGROUND: Oral tongue squamous cell carcinomas (TSCC) are a unique subset of head and neck cancers with a distinct demographic profile, where up to half of the cases are never smokers. A small proportion of patients with OSCC are known to respond to EGFR TKI. We used a high-sensitivity mass spectrometry-based mutation profiling platform to determine the EGFR mutation status, as well as other actionable alterations in a series of Asian TSCC. METHODS: 66 TSCC patients treated between 1998-2009 with complete clinico-pathologic data were included in this study. Somatic mutation profiling was performed using Sequenom LungCarta v1.0, and correlated with clinical parameters. RESULTS: Mutations were identified in 20/66(30.3%) of samples and involved TP53, STK11, MET, PIK3CA, BRAF and NRF2. No activating EGFR mutations or KRAS mutations were discovered in our series, where just over a third were never smokers. The most common mutations were in p53 (10.6%; n = 7) and MET (10.6%, n = 11) followed by STK11 (9.1%, n = 6) and PIK3CA (4.5%, n = 3). BRAF and NRF2 mutations, which are novel in TSCC, were demonstrated in one sample each. There was no significant correlation between overall mutation status and smoking history (p = 0.967) or age (p = 0.360). Positive MET alteration was associated with poorer loco-regional recurrence free survival (LRFS) of 11 months [vs 90 months in MET-negative group (p = 0.008)]. None of the other mutations were significantly correlated with LRFS or overall survival. Four of these tumors were propagated as immortalized cell lines and demonstrated the same mutations as the original tumor. CONCLUSIONS: Using the Sequenom multiplexed LungCarta panel, we identified mutations in 6 genes, TP53, STK11, MET, PIK3CA, BRAF and NRF2, with the notable absence of EGFR and HER2 mutations in our series of Asian OSCC. Primary cell line models recapitulated the mutation profiles of the original primary tumours and provide an invaluable resource for experimental cancer therapeutics.

Targeting cancer stem cell plasticity through modulation of epidermal growth factor and insulin-like growth factor receptor signaling in head and neck squamous cell cancer.

Emerging data suggest that cancer stem cells (CSCs) exist in equilibrium with differentiated cells and that stochastic transitions between these states can account for tumor heterogeneity and drug resistance. The aim of this study was to establish an in vitro system that recapitulates stem cell plasticity in head and neck squamous cell cancers (HNSCCs) and identify the factors that play a role in the maintenance and repopulation of CSCs. Tumor spheres were established using patient-derived cell lines via anchorage-independent cell culture techniques. These tumor spheres were found to have higher aldehyde dehydrogenase (ALD) cell fractions and increased expression of Kruppel-like factor 4, SRY (sex determining region Y)-box 2, and Nanog and were resistant to γ-radiation, 5-fluorouracil, cisplatin, and etoposide treatment compared with monolayer culture cells. Monolayer cultures were subject to single cell cloning to generate clones with high and low ALD fractions. ALDHigh clones showed higher expression of stem cell and epithelial-mesenchymal transition markers compared with ALDLow clones. ALD fractions, representing stem cell fractions, fluctuated with serial passaging, equilibrating at a level specific to each cell line, and could be augmented by the addition of epidermal growth factor (EGF) and/or insulin. ALDHigh clones showed increased EGF receptor (EGFR) and insulin-like growth factor-1 receptor (IGF-1R) phosphorylation, with increased activation of downstream pathways compared with ALDLow clones. Importantly, blocking these pathways using specific inhibitors against EGFR and IGF-1R reduced stem cell fractions drastically. Taken together, these results show that HNSCC CSCs exhibit plasticity, with the maintenance of the stem cell fraction dependent on the EGFR and IGF-1R pathways and potentially amenable to targeted therapeutics.