Anaplastic Lymnhoma Kinase(ALK)Reegulates TGF-? Signaling In Tumorigenesis

Nowadays cancer has gradually become the most frequent and dangerous disease in the whole world,thus it is urgent to thoroughly investigate its pathology and biological properties.According to decades of scientific researches,tumors acquire many capabilities making them different from normal tissues,including evading growth suppressors.TGF-? exerts broad control over many biological processes including cell proliferation,differentiation,extracellular matrix formation,immune response and so on.Under normal physiological state,TGF-P restrains the growth of epithelial and hematopoietic cells.Therefore in the early stage of cancer development,it acts as an important tumor suppressive signaling.In turn tumor cells gain many strategies to evade the surveillance of TGF-?.For example,SMAD4/DPC4,the central player in TGF-? signaling transduction,is frequently deleted or mutated in pancreatic gastrointestinal and cancers,which leads to TGF-? resistance.However,variation of Smad4 gene is rare in most other cancer types,indicating there are other specific mechanisms regulating the inactivation of TGF-? signaling.SMAD4 is a key member in the integral TGF-?-SMAD signal pathway,for it is the unique Co-SMAD and a tumor suppressor which is modified by many regulators.Therefore we start to screen SMAD4-interacting candidates to examine the crosstalk between TGF-? and other cell signaling in the context of cancersAccording to our lab's previous study,we discovered Anaplastic Lymphoma Kinase(ALK),an oncogenic tyrosine kinase that directly phosphorylates SMAD4,eliminates its tumor-suppressing activity and consequently alleviates TGF-? tumor suppressing responses.ALK is consistently activated by point-mutation and chromosome translocation in numerous cancers,including anaplastic large cell lymphoma(ALCL),non-small cell lung carcinomas(NSCLC)diffuse large B-cell lymphoma(DLBL),inflammatory breast cancer(IBC),and glioblastoma multiform(GBM).In this study,we investigated the mechanism of TGF-? resistance in ALK-positive tumors in depth.We demonstrate that not only NPM-ALK in ALCL,but also EML4-ALK in NSCLC and ALK-F1174L in neuroblastoma could phosphorylate SMAD4 and inhibit TGF-? signaling,indicating the extensive function of ALK kinase on TGF-? in tumors.Molecular analysis shows that the tyrosine-phosphorylation of SMAD4 has no influence on SMADs complex formation and nuclear import,neither on association with transcription co-factor p300/CBP.Instead it compromises SMAD4's DNA-binding ability,thus undermines the efficiency of SMADs complex targeting promoter regions of downstream genes.To go further,we conclude the suppression of TGF-? signaling is required for ALK-induced tumorigenesis.On one hand we did nude mice xenograft experiments with ALK-positive ALCL cells.If SMAD4 is not endogenously phosphorylated in tumor cells,it will activate TGF-(3 signal pathway and repress tumor growth.On the other hand,we verified pY-SMAD4 correlates with the presence of NPMALK in human lymphomas with IHC experiments on human lymphoma specimens.These findings reveal a potential mechanism how the ALK escape from TGF-? tumor suppression to facilitate tumorigenesis.At last we research on the effect of ALK exerting on TGF-?-induced EMT.Data manifested ALK enhanced the EMT caused by TGF-?.Moreover ALK alone will stimulate mesenchymal properties of epithelial cells.Thus more investigations are demanded to figure out the underlying mechanism of how ALK functions on TGF-?-induced EMT.In all,ALK performs as a SMAD4 tyrosine kinase to encourage its tumourigenic capacity is of great significance and novelty.Our study confirms this regulation in various ALK-positive cancers,including NSCLC and neuroblastoma with aberrantly activated ALK accumulation.This study should be of significance in understanding the pathology of ALK-induced cancers and the regulation of TGF-? during the process of tumor development.It will also guide the strategies for the prevention and treatment of diseases involving ALK and TGF-?.It is conceivable that SMAD4 is phosphorylated by other hyperactive tyrosine kinases associated with tumourigenesis.And this non-mutational inactivation of SMAD4 may be popular in a diversity of cancers.Therefore SMAD4 tyrosine phosphorylation could probably be a general biomarker denoting TGF-? resistance and tumor malignancy.