ELAVL4 promotes the tumorigenesis of small cell lung cancer by stabilizing LncRNA LYPLAL1-DT and enhancing profilin 2 activation

Small cell lung cancer (SCLC) is one of the most malignant tumors that has an extremely poor prognosis. RNA-binding protein (RBP) and long noncoding RNA (lncRNA) have been shown to be key regulators during tumorigenesis as well as lung tumor progression. However, the role of RBP ELAVL4 and lncRNA LYPLAL1-DT in SCLC remains unclear. In this study, we verified that lncRNA LYPLAL1-DT acts as an SCLC oncogenic lncRNA and was confirmed in vitro and in vivo. Mechanistically, LYPLAL1-DT negatively regulates the expression of miR-204-5p, leading to the upregulation of PFN2, thus, promoting SCLC cell proliferation, migration, and invasion. ELAVL4 has been shown to enhance the stability of LYPLAL1-DT and PFN2 mRNA. Our study reveals a regulatory pathway, where ELAVL4 stabilizes PFN2 and LYPLAL1-DT with the latter further increasing PFN2 expression by blocking the action of miR-204-5p. Upregulated PFN2 ultimately promotes tumorigenesis and invasion in SCLC. These findings provide novel prognostic indicators as well as promising new therapeutic targets for SCLC.

[Profilin 2 is highly expressed in gastric cancer and promotes tumor cell proliferation and migration]

OBJECTIVE

To investigate the expression of profilin 2 (PFN2) in gastric cancer and assess its potential value as a novel prognostic indicator and a therapeutic target.

METHODS

We collected gastric cancer and paired adjacent tissues from 100 patients for immunohistochemical detection of PFN2 expression. According to the expression level of PFN2, the patients were divided into two groups with high (46 cases) and low (48 cases) PNF2 expression in cancer tissues, and also into two groups with high (26 cases) and low (49 cases) PNF2 expression in adjacent tissues. Chi-square test, Spearman correlation and KaplanMeier survival analysis were used to analyze the relationship between PFN2 protein expression level and the patients' clinical parameters. We also tested the effects of PFN2 knockdown and overexpression on the proliferation and migration of MKN-45 cells using Transwell assay and CCK-8 assay.

RESULTS

The expression of PFN2 protein was significantly higher in gastric cancer tissues than in adjacent tissues (P < 0.01). PFN2 expression was positively correlated with M-stage of gastric cancer and VEGFR expression in the tumor tissues (P < 0.01). A high expression of PFN2 protein was significantly correlated with a poor prognosis of gastric cancer patients (P < 0.01), and was an independent predictor of the prognosis of gastric cancer. In MKN-45 cells, the cells overexpressing PFN2 showed significantly stronger proliferation and migration abilities than those with PFN2 knockdown (P < 0.001).

CONCLUSION

PFN2 protein is highly expressed in gastric cancer tissues to promote the proliferation and migration of the tumor cells. PFN2 may serve as a potential diagnostic marker, a prognostic indicator and a therapeutic target for gastric cancer.

Profilin 2 promotes growth, metastasis, and angiogenesis of small cell lung cancer through cancer-derived exosomes

Small cell lung cancer (SCLC) is highly aggressive and prone to hypervascular metastases. Recently, we found profilin 2 (PFN2) expression in SCLC but not in normal tissues. Furthermore, PFN2 expression had been shown to promote angiogenesis through exosomes. However, it remains unclear whether PFN2 contributes to the progression and metastasis of SCLC through angiogenesis. We report here that overexpression (OE) of PFN2 increased, whereas its knockdown (KD) decreased the proliferation, migration, and invasion of SCLC cell H446. The exosomes from OE-H446 (SCLC-OE-exo) exhibited similar effects on H446 properties. Culturing of endothelial cells (ECs) in SCLC-OE conditioned medium (CM) or SCLC-OE-exo increased the migration and tube formation ability of ECs, whereas SCLC-KD-CM and SCLC-KD-exo had inhibitory effects. Interestingly, both SCLC- and EC-derived exosomes were internalized in H446 more rapidly than in ECs. More importantly, OE-PFN2 dramatically elevated SCLC growth and vasculature formation as well as lung metastasis in tumor xenograft models. Finally, we found that PFN2 activated Smad2/3 in H446 and pERK in ECs, respectively. Taken together, our study revealed the role of PFN2 in SCLC development and metastasis, as well as tumor angiogenesis through exosomes, providing a new molecular target for SCLC treatment.