Imbalanced LIMK1 And LIMK2 Expression Leads To Human Colorectal Cancer Progression And Metastasis Via Promoting β-Catenin Nuclear Translocation

Colorectal cancer(CRC)is one of most common cancers and the leading causes of cancer death in China,with a growth rate that is twice that of the world average.CRC is a heterogeneous disease and usually occurs from precancerous lesions.Serrated adenoma(SA)is a type of adenoma with serrated crypt structure,including hyperplastic polyps(HP),sessile serrated adenoma/polyp(SSA/P)and traditional serrated adenoma(TSA).SA is a kind of precancerous lesion and has high incidence of CRC,especially the SSA/P subtype.Activation of the Wnt signaling pathway contributes to the malignant transformation of SA.By improving our understanding of the process of SA transitioning into CRC,we may propose an effective marker for tumor progression.For CRC patients,metastasis is a noteworthy cause of lethality.CRC metastasis is a multi-step,multi-stage,polygene process,and the molecular framework that involves tumor metastasis has been found in recent years.However,there are limited effective biomarkers for early tumor metastasis.Hence,it is still important to uncover the molecular mechanism underlying CRC metastasis.The LIM domain can combine with proteins,and the kinase can phosphorylate downstream genes.Two distinct protein kinases belong to the LIMK family:LIMK1 and LIMK2.Previous studies have identified LIMK1 as a cancer-promoting regulator in CRC.Interestingly,our previous study found that LIMK2 displays an opposite expression level to that of LIMK1 in CRC.The correlation between LIMK1 and LIMK2 has not been characterized before.Therefore,we suppose that LIMK2 may serve a different role than LIMK1 in CRC development.Previously,studies have identified the Wnt signaling pathway as a key signaling pathway involved in many processes of CRC.The Wnt signaling pathway comprises two pathways:the canonical Wnt signaling pathway and the non-canonical Wnt signaling pathway.B-Catenin is a crucial regulator of canonical Wnt signaling via controlling a cluster of genes,including MMP-7,c-myc,Met,c-Jun and so on.Results1.LIMK2 is progressively down-regulated in human CRC tissuesLIMK2 was down-regulated in CRC tissues compared with the LIMK2 expression in the adjacent normal tissues.LIMK2 was reduced in SA and CRC tissues to various degrees,and LIMK2 expression was progressively down-regulated with the advancement of tumor development.Compared with the relatively low metastatic potential cell lines,such as SW480 and HCT116,LIMK2 was significantly reduced in the LoVo and SW620 cell lines with a relatively high metastatic potential.2.Reduced LIMK2 contributes to aggressive phenotypes of cell lines in vitroWound healing and transwell assays revealed that knocking down LIMK2 increased the migration and invasion abilities of CRC cells.Conversely,overexpression of LIMK2 achieved the opposite effect.Silencing LIMK2 accelerated the G1-S phase transition,while LIMK2 overexpression arrested the G1-S phase transition.3.After knocking down LIMK2,mesenchymal marker(Vimentin)was upregulated,while the epithelial marker(E-cadherin)was down-regulated.4.Knocking down LIMK2 promotes p-Catenin nuclear translocation and activates the Wnt/β-Catenin signaling pathway5.LIMK2 shows the negative correlation with LIMK1,and imbalanced LIMK1 and LIMK2 promotes CRC aggression via regulating the Wnt/β-Catenin signaling pathwayConclusion:In summary,we observed progressive down-regulation of LIMK2 from normal colon mucosa to SA tissue to CRC tissue,and LIMK2 was especially associated with tumor progression,suggesting its relation to tumor progression.Knocking down LIMK2 promoted CRC cell EMT-induced metastasis and accelerated the G1-S transition via activating the Wnt signaling pathway.LIMK2 led to β-Catenin concentration in the cytoplasm,while LIMK1 accelerated β-Catenin nuclear translocation.The imbalanced expression of LIMK1 and LIMK2 could cooperate in the accumulation ofβ-Catenin and thus the activation of a potential oncogenic process(figure 7).This study provides not only new insights into the molecular mechanism of tumor progression but also new clues for LIMK-based specific target drugs.