DNA methylation patterns at and beyond the histological margin of early-stage invasive lung adenocarcinoma radiologically manifested as pure ground-glass opacity.

BACKGROUND: Early-stage lung cancers radiologically manifested as ground-glass opacities (GGOs) have been increasingly identified, among which pure GGO (pGGO) has a good prognosis after local resection. However, the optimal surgical margin is still under debate. Precancerous lesions exist in tumor-adjacent tissues beyond the histological margin. However, potential precancerous epigenetic variation patterns beyond the histological margin of pGGO are yet to be discovered and described. RESULTS: A genome-wide high-resolution DNA methylation analysis was performed on samples collected from 15 pGGO at tumor core (TC), tumor edge (TE), para-tumor tissues at the 5 mm, 10 mm, 15 mm, 20 mm beyond the tumor, and peripheral normal (PN) tissue. TC and TE were tested with the same genetic alterations, which were also observed in histologically normal tissue at 5 mm in two patients with lower mutation allele frequency. According to the difference of methylation profiles between PN samples, 2284 methylation haplotype blocks (MHBs), 1657 differentially methylated CpG sites (DMCs), and 713 differentially methylated regions (DMRs) were identified using reduced representation bisulfite sequencing (RRBS). Two different patterns of methylation markers were observed: Steep (S) markers sharply changed at 5 mm beyond the histological margin, and Gradual (G) markers changed gradually from TC to PN. S markers composed 86.2% of the tumor-related methylation markers, and G markers composed the other 13.8%. S-marker-associated genes enriched in GO terms that were related to the hallmarks of cancer, and G-markers-associated genes enriched in pathways of stem cell pluripotency and transcriptional misregulation in cancer. Significant difference in DNA methylation score was observed between peripheral normal tissue and tumor-adjacent tissues 5 mm further from the histological margin (p < 0.001 in MHB markers). DNA methylation score at and beyond 10 mm from histological margin is not significantly different from peripheral normal tissues (p > 0.05 in all markers). CONCLUSIONS: According to the methylation pattern observed in our study, it was implied that methylation alterations were not significantly different between tissues at or beyond P10 and distal normal tissues. This finding explained for the excellent prognosis from radical resections with surgical margins of more than 15 mm. The inclusion of epigenetic characteristics into surgical margin analysis may yield a more sensitive and accurate assessment of remnant cancerous and precancerous cells in the surgical margins.

HER2 transmembrane domain mutation: comprehensive characteristics and real-world evidence of treatment response in Chinese lung adenocarcinoma.

BACKGROUND: HER2 transmembrane domain (TMD) mutation has been reported as a rare driver mutation associated with advanced stage disease and a poor prognosis in patients with lung adenocarcinoma (LUAD). We aimed to comprehensively profile the genetic landscape and treatment response information of HER2 TMD-mutant LUAD. METHODS: An in-house database of 7,812 LUAD patients was screened for mutation prevalence. A multi-center cohort of 16 HER2 V659E-mutant patients and an external cohort of 38 HER2-mutant patients from cBioPortal with overall survival (OS) data were analyzed. Eight patients from the in-house cohort were included in the real-world study of treatment response. Molecular docking simulation and binding affinity prediction were performed. RESULTS: In Chinese LUAD, the prevalence of HER2 TMD mutation was 0.18% (14/7,812), and 0.14% (11/7,812) for the HER2 V659E mutation. The most recurrent co-alteration was TP53 mutation (n=4, 25%) and HER2 amplification (n=2, 12.5%). TMD-mutant patients were diagnosed at more advance stages (P<0.001) and had poorer OS (median OS 10.0 vs. 61.6 months, HR =7.9, 95% CI: 1.0-61.0, P<0.001) than non-TMD mutations. The overall response rate of targeted therapy, chemo-based therapy, and immunotherapy was 57.1%, 22.2%, and 0%, respectively. We postulated to challenge the resistance of tyrosine kinase inhibitor (TKI) with another with stronger binding energy to HER2 and supported the conclusion with a successful case. Additionally, we demonstrated a three-month response to the off-label use of pyrotinib in fifth-line therapy. CONCLUSIONS: Comapred with non-TMD mtuations, HER2 TMD mutation is a rare driver mutation with poorer prognosis in LUAD. Targeted therapy is the dominant choice for patients harboring this targetable mutation and longer OS could possibly be achieved through rechallenge with TKI of stronger binding affinity. Response to fifth-line pyrotinib was observed.