The KLF6 splice variant KLF6-SV1 promotes proliferation and invasion of non-small cell lung cancer by up-regultating PI3K-AKT signaling pathway

Abstract

Non-small cell lung cancer (NSCLC) is an aggressive type of lung malignancy. Most of the patients have poor prognosis. Increasing evidence has revealed an association between KLF6-SV1, known as an oncogenic splice variant of KLF6, and metastatic potential or poor prognosis in many cancers. We previously demonstrated the increased KLF6-SV1 expression in NSCLC samples. There was a significant association between increased expression of KLF6-SV1 with the pN and pTNM stages and poor survival in NSCLC patients. In the present study, we aimed to further investigate the functional role of KLF6-SV1 in the progression of NSCLC. SK-MES-1 cells were infected with Lenti-virus containing KLF6-SV1 to up-regulate its expression, and the small interfering RNA (siRNA) was designed to knock down KLF6-SV1 transcript level in A549 cells. CCK8, colony formation, wound-healing, and transwell assays were performed to examine cell proliferation, migration, and invasion respectively. Western blot assay was used to detect the expression or phosphorylation of related proteins. We found that in vitro silencing of KLF6-SV1 by siRNA inhibited A549 cell proliferation, migration, and invasion through changes in E-cadherin, N-cadherin, Vimentin, Snail1 and Snail2 expression. Furthermore, KLF6-SV1 isoform knockdown triggered caspase-dependent apoptosis of A549 cells through downregulation of the phosphatidylinositol 3-OH kinase (PI3K)/Akt signaling pathway and apoptosis-related protein expression. Overexpression of KLF6-SV1 transcript induced significant increase in proliferation, migration, invasion and changes in expression of related proteins. Our study support KLF6-SV1 might be an important player in modulating the growth, migration, invasion, and survival of NSCLC cells, and that silencing KLF6-SV1 siRNA has the potential to be a powerful gene therapy strategy for NSCLC.

Krüppel-Like Factor 6 Splice Variant 1: An Oncogenic Transcription Factor Involved in the Progression of Multiple Malignant Tumors

“…With further studies of lung cancer, researchers found that E-cadherin expression was reduced in clones of SK-MES-1 cells upregulated by KLF6-SV1, while SNAIL1, SNAIL2, Vimentin, and N-cadherin expression were significantly increased. On the contrary, after transfection of KLF6-SV1 siRNA into A549 cells, the expression of E-cadherin was up-regulated, while the expressions of N-cadherin, Vimentin, SNAIL1, and SNAIL2 were down-regulated, which further proves that KLF6-SV1 may mediate the occurrence and development of related tumors by regulating EMT activation transcription factors ( Zhang et al, 2019 ).…”

“…Hepatocyte-specific deletion of KLF6 promoted the enhancement of proliferation, while KLF6-SV1 overexpression largely caused the increase in tumor grade ( Vetter et al, 2012 ). Moreover, Zhang et al (2019) found that KLF6-SV1 can regulate the PI3K-AKT signaling pathway and the Bcl-2/Bax axis in non-small cell lung carcinoma (NSCLC), resulting in promoting tumor cell proliferation.…”

“…The first hot topic in academia is KLF6-SV1-associated tumor cell proliferation, invasion, metastasis, and prognosis. A considerable number of small-sample studies are involved in a variety of human malignant tumors, such as prostate cancer ( Narla et al, 2008 , 2005a , b ), lung cancer ( DiFeo et al, 2008 ; Sangodkar et al, 2009 ; Zhang et al, 2018 , 2019 ; Wang et al, 2019 ), breast cancer ( Hatami et al, 2013 ), ovarian cancer ( DiFeo et al, 2006b , 2009a , c ), gastric cancer ( Chen et al, 2011 ), etc. ( Table 1 ).…”

Two Sides of the Same Coin: The Roles of KLF6 in Physiology and Pathophysiology

“…Whilst the full-length KLF6 is established as a tumour suppressor in many cancer types, KLF6-SV1 is deemed to be pro-oncogenic by antagonising the full-length KLF6 functions in a dominant-negative manner. KLF6-SV1 has been reported to promote the progression and associate with a poor prognosis of the following cancer types: prostate [ 118 , 119 ], breast [ 120 ], ovarian [ 121 ] and lung cancer cells [ 122 , 123 ]. Intriguingly, KLF6-SV2, which also lacks the NLS domain, was downregulated in colorectal and liver cancers and possessed the tumour suppressive roles.…”

“…Pro-oncogenic by promoting the progression and association with poor prognosis in prostate [ 118 , 119 ], breast [ 120 ], ovarian [ 121 ] and lung cancers [ 122 , 123 ].…”