HER3 overexpression: a predictive marker for poor prognosis in advanced ALK-positive non-small cell lung cancer treated with ALK inhibitors

Abstract

Background: Anaplastic lymphoma kinase (ALK)-targeted tyrosine kinase inhibitors (TKIs) improve patient survival; however, some patients develop ALK-TKI resistance with unidentified mechanisms. We investigated ErbB family and c-MET expression in patients with ALK-positive non-small cell lung cancer (NSCLC) to understand their roles in the ALK-TKI response.

Methods: We studied 72 patients with advanced ALK-positive NSCLC with EML4-ALK fusion variant subtyping and immunostaining for c-MET, EGFR, HER2, and HER3 on tissue specimens both pre- (primary) and post-treatment (secondary) with ALK-TKI. We investigated the association of their expression with survival outcomes and assessed the effectiveness of combining ALK and EGFR inhibitors in ALK-positive NSCLC cell lines stimulated with the HER3-specific ligand HRG1.

Results: High expression of c-MET, EGFR, HER2, and HER3 was observed in 4.9%, 18.0%, 1.6%, and 25.8% of primary tumors, respectively, and 18.5%, 37.0%, 10.7%, and 35.7% of secondary tumors, respectively. HER3 overexpression in primary tumors showed inferior survival (P=0.132). In the subgroup with EML4-ALK variant 1/2 (V1/V2), HER3 overexpression was significantly associated with inferior survival in both primary and secondary tumors (P=0.022 and P=0.004, respectively). Combination treatment with lorlatinib and erlotinib significantly reduced HRG1-induced activation of RTK signaling in ALK-positive NSCLC cells.

Conclusions: HER3 overexpression has potential as a prognostic marker in ALK-positive NSCLCs, including ALK-TKI naïve and treated cases, especially those with EML4-ALK V1/V2. Assessing HER3 expression may be crucial for treatment planning and outcome prediction in these patients.

Keywords: EGFR; EML4-ALK; HER3; Non-small cell lung cancer (NSCLC); c-MET.

Figure 1

Flow diagram of the cohort selection. ^a, one patient was additionally excluded due to limited tissue availability for the c-MET and EGFR analysis; ^b, patients who received crizotinib without further generations of ALK inhibitors during the follow-up; ^c, patients who received second- or third-generation ALK inhibitors as any line of therapy during the follow-up. NSCLC, non-small cell cancer; ALK, anaplastic lymphoma kinase.

Figure 2

Expression of c-MET, EGFR, HER2, and HER3 in ALK-positive non-small cell lung cancers. Representative immunohistochemistry images (magnification ×400) with scoring (A). For c-MET and EGFR, scores 0, 1, and 2 were low expression, while a score of 3 indicated high expression. For HER2 and HER3, scores 0 and 1 represented low expression, while scores 2 and 3 were high expression. Proportion of low and high expression in primary (n=61) and secondary (n=62) tumor specimens (B). High expression rates in primary tumors were 4.9% for c-MET, 18.0% for EGFR, 1.6% for HER2, and 25.8% for HER3. In secondary tumors, high expression rates were 18.5% for c-MET, 37.0% for EGFR, 10.7% for HER2, and 35.7% for HER3. ALK, anaplastic lymphoma kinase; N/A, not applicable.

Figure 3

Kaplan-Meier survival plots of 5-year overall survival in ALK-positive non-small cell lung cancer patients treated with second- or third-generation ALK inhibitors. The log-rank tests compared high and low expression levels of c-MET (A), EGFR (B), and HER3 (C) in primary tumors and those of c-MET (D), EGFR (E), HER2 (F), and HER3 (G) in secondary tumors. In the variant 1/2 subgroup, log-rank tests compared high and low expression levels of EGFR (H) and HER3 (I) in primary tumors and those of c-MET (J), EGFR (K), HER2 (L), and HER3 (M) in secondary tumors. ALK, anaplastic lymphoma kinase.

Figure 4

The activation of multiple signaling pathways, including HER3, induced by HRG1 treatment, and the effects of ALK- or EGFR-tyrosine kinase inhibitors in H3122 (EML4-ALK variant 1) and H2228 (EML4-ALK variant 3a/b) cell lines. Cells were pre-treated with HRG1 (10 nM) for 4 hours followed by lorlatinib (Lor), Erlotinib (Erl), or a combination of both for 2 hours. ALK, anaplastic lymphoma kinase.