PARP-1 induces EMT in non-small cell lung carcinoma cells via modulating the transcription factors Smad4, p65 and ZEB1

AIM

To study the role of PARP-1 in EMT of non-small cell lung carcinoma.

MATERIALS AND METHODS

We used H1299 and H460 lung cancer cells for knockdown study of PARP-1 using shPARP-1 lentiviral particle. We performed western blotting, confocal microscopy, semi-quantitative PCR, wound healing and colony formation assays.

BACKGROUND AND KEY FINDINGS

PARP-1 (poly-ADP ribose polymerase-1) is a multi-domain protein having DNA binding, auto-modification and catalytic domain, that participates in many biological processes including DNA damage detection and repair, transcription regulation, apoptosis, necrosis, cancer progression and metastasis. Metastasis is a leading cause of death in cancer patients, which starts in epithelial tumors via initiating epithelial to mesenchymal transition. There are various transcription factors involved in EMT including Snail-1, Smads, p65, ZEB1 and Twist1. We studied the effect of PARP-1 knockdown on EMT in non-small cell lung cancer cell line H1299. We found a significant increase in epithelial marker including ZO1 and β-catenin, while prominent decrease in the mesenchymal marker vimentin after PARP-1 knockdown in H1299 cells. Transcription factors including p65, Smad4 and ZEB1 showed significant decrease with concurrent expression of EMT markers. Cell migration and colony formation decreased after PARP-1 knockdown in H1299 cells.

SIGNIFICANCE

Overall, the shRNA mediated knockdown of PARP-1 in H1299 cells resulted in reversal of EMT or mesenchymal to epithelial transition (MET) characterized by an increase in epithelial markers and a decrease in mesenchymal markers, via down-regulating transcription factors including Smad4, p65 and ZEB1. Thus PARP-1 has a role in EMT in lung cancer.

Epithelial-Mesenchymal Transition in the Resistance to Somatostatin Receptor Ligands in Acromegaly

Epithelial-mesenchymal transition (EMT) is a dynamic process by which epithelial cells loss their phenotype and acquire mesenchymal traits, including increased migratory and invasive capacities. EMT is involved in physiological processes, such as embryogenesis and wound healing, and in pathological processes such as cancer, playing a pivotal role in tumor progression and metastasis. Pituitary tumors, although typically benign, can be locally invasive. Different studies have shown the association of EMT with increased tumor size and invasion in pituitary tumors, and in particular with a poor response to Somatostatin Receptor Ligands (SRLs) treatment in GH-producing pituitary tumors, the main cause of acromegaly. This review will summarize the current knowledge regarding EMT and SRLs resistance in acromegaly and, based on this relation, will suggest new biomarkers and possible therapies to SRLs resistant tumors.

Impact of SLC20A1 on the Wnt/β‑catenin signaling pathway in somatotroph adenomas

Studies have revealed that genetic and functional aberrations of oncogenes, tumor‑suppressor genes, signaling pathways and receptors are among the most prominent events in pituitary tumorigenesis, and a potent biomarker would be helpful for early diagnosis, subsequent treatment and disease control. The present study investigated the expression signatures of solute carrier family 20 member 1, also known as phosphate transporter 1 (SLC20A1) and the Wnt/β‑catenin signaling pathway in 52 patients with somatotroph adenomas. According to immunohistochemistry analysis, the H‑score of SLC20A1 was 222.6±15.2 in invasive tumor samples and 144.5±30.4 in non‑invasive tumor samples (P<0.01), while the H‑scores of β‑catenin were 210.1±21.4 and 134.9±32.7, respectively (P<0.05). The H‑scores of Wnt inhibitory factor 1 (Wif1) exhibited the opposite trend, with scores of 134.5±22.7 and 253.6±14.8, respectively (P<0.01). The H‑scores of SLC20A1 were negatively associated with those of Wif1 in somatotroph adenomas (correlation coefficient r=‑0.367). The mean progression‑free survival in the low SLC20A1 group was longer than that in the group with high SLC20A1 H‑scores (P=0.024). Reverse transcription‑quantitative PCR (RT‑qPCR) and western blotting confirmed the interference efficiency of the segments short hairpin (Sh)‑B‑SLC20A1 and Sh‑C‑SLC20A1. Cell proliferation experiments revealed that the cell viability of the Sh‑B‑SLC20A1 group was 76.3±4.5, 65.7±3.7 and 53.1±3.2% of that of control GH3 cells after 24, 48 and 72 h of transfection, respectively, while the cell viability of the Sh‑C‑SLC20A1 group was 86.4±5.7, 75.6±4.4 and 67.5±3.8%, respectively (P<0.05). ELISA analysis demonstrated the growth hormone (GH) levels in the Sh‑B‑SLC20A1 and Sh‑C‑SLC20A1 groups to be 34.7±10.4 and 54.6±14.4%, respectively, of that of control GH3 cells (P<0.05). The transmembrane invasion assay revealed that knocking down SLC20A1 significantly suppressed cell invasion in the Sh‑B‑SLC20A1 and Sh‑C‑SLC20A1 groups. RT‑qPCR and western blotting demonstrated that Sh‑B‑SLC20A1 and Sh‑C‑SLC20A1 evidently increased the levels of Wif1 and secreted frizzled‑related protein 4. The present data suggested that SLC20A1 levels are positively associated with tumor size, invasive behavior and tumor recurrence in somatotroph adenomas. Furthermore, SLC20A1 may be associated with the activation of the Wnt/β‑catenin signaling pathway.