Increase of secondary mutations may be a drug-resistance mechanism for lung adenocarcinoma after radiation therapy combined with tyrosine kinase inhibitor

Angiogenic activities are increased via upregulation of HIF-1α expression in gefitinib-resistant non-small cell lung carcinoma cells

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) have been used to treat patients with non-small cell lung cancer (NSCLC) and activating EGFR mutations; however, the emergence of secondary mutations in EGFR or the acquisition of resistance to EGFR-TKIs can develop and is involved in clinical failure. Since angiogenesis is associated with tumor progression and the blockade of antitumor drugs, inhibition of angiogenesis could be a rational strategy for developing anticancer drugs combined with EGFR-TKIs to treat patients with NSCLC. The signaling pathway mediated by hypoxia-inducible factor-1 (HIF-1) is essential for tumor angiogenesis. The present study aimed to identify the dependence of gefitinib resistance on HIF-1α activity using angiogenesis assays, western blot analysis, colony formation assay, xenograft tumor mouse model and immunohistochemical analysis of tumor tissues. In the NSCLC cell lines, HIF-1α protein expression levels and hypoxia-induced angiogenic activities were found to be increased. In a xenograft mouse tumor model, tumor tissues derived from gefitinib-resistant PC9 cells showed increased protein expression of HIF-1α and angiogenesis within the tumors. Furthermore, inhibition of HIF-1α suppressed resistance to gefitinib, whereas overexpression of HIF-1α increased resistance to gefitinib. The results from the present study provides evidence that HIF-1α was associated with the acquisition of resistance to gefitinib and suggested that inhibiting HIF-1α alleviated gefitinib resistance in NSCLC cell lines.

Radioresistant Nasopharyngeal Carcinoma Cells Exhibited Decreased Cisplatin Sensitivity by Inducing SLC1A6 Expression

Cisplatin-based regimens are commonly used for the treatment of nasopharyngeal carcinoma (NPC) in patients who receive concurrent chemoradiotherapy. The sensitivity of NPC cells to cisplatin is closely associated with the efficacy of radiation therapy. In this study, we established two radioresistant NPC cell lines, HONE1-IR and CNE2-IR, and found that both cell lines showed reduced sensitivity to cisplatin. RNA-sequence analysis showed that SLC1A6 was upregulated in both HONE1-IR and CNE2-IR cell lines. Downregulation of SLC1A6 enhanced cisplatin sensitivity in these two radioresistant NPC cell lines. It was also found that the expression of SLC1A6 was induced during radiation treatment and correlated with poor prognosis of NPC patients. Notably, we observed that upregulation of SLC1A6 led to elevating level of glutamate and the expression of drug-resistant genes, resulted in reduced cisplatin sensitivity. Our findings provide a rationale for developing a novel therapeutic target for NPC patients with cisplatin resistance.

C1q-like 1 is frequently up-regulated in lung adenocarcinoma and contributes to the proliferation and invasion of tumor cells

This study aims to investigate the effects of C1q-like 1 (C1QL1) on the growth and migration of lung adenocarcinoma (LUAD) cells and the underlying mechanism. The expression of C1QL1 in LUAD tissues and its prognostic value were analyzed using the data from The Cancer Genome Atlas (TCGA) database. To investigate the function of C1QL1, loss-of-function and gain-of-function assays were conducted in Calu-3 cells and LTEP-a-2 cells, respectively. Cell growth was evaluated by CCK-8 and colony formation assays. Transwell assays were performed to assess cell invasive and migratory abilities. qRT-PCR and Western blotting were performed to detect RNA and protein expression, respectively. Firstly, we found that C1QL1 was highly expressed and predicted poor outcomes in LUAD patients from TCGA database. Moreover, the mRNA and protein expression levels of C1QL1 were higher in LUAD cells than that in normal lung cells. Results of functional experiments illustrated that depletion of C1QL1 restrained the growth, invasion and migration of Calu-3 cells, meanwhile over-expression of C1QL1 presented the opposite results in LTEP-a-2 cells. Furthermore, we discovered that down-regulation of C1QL1 elevated the protein level of E-cadherin and reduced the protein levels of N-cadherin, Vimentin and Snail in Calu-3 cells, whereas over-expression of C1QL1 led to the opposite outcomes in LTEP-a-2 cells. Our data indicated that C1QL1 functioned as a crucial driver in LUAD cell growth and motility, which might be achieved by modulating epithelial-mesenchymal transition (EMT). These consequences are of important relevance for the design of therapeutic strategies for LUAD.