The Role And Mechanism Of Mutated TGF-βRⅡ In Human Bladder Cancer Growth, Invasion And Metastasis

【Objective】Transforming growth factor beta 1 (TGF-β1) mediates growth inhibitory effect through the receptor pathway composed of TGF-βreceptor typeⅡ(TGF-βRⅡ)和TGF-βreceptor typeⅠ(TGF-βRⅠ). To overcome this advantage, tumor cells adapt the strategy by downregulating or mutaionanlly inactivating TGF-βreceptors. However, TGF-β1-triggered signaling also has a protumor effect through promotion of tumor cell migration, named "The TGF-βParadox". We aim to find how the mutative state including altered expression level of TGF-βRⅡaffect on bladder cancer, and may provide new evidence for treatment of bladder cancer patients.\【METHODS】1. Expression of TGF-β1 and TGF-βRⅡin several kinds of tumor cell lines1) Expression of TGF-βRⅠ, TGF-βRⅡand TGF-β1 in human cancer cell lines (breast cancer, hepatocarcinoma, lung cancer, gastric cancer, cervical cancer, Leukemia, prostate cancer, melanoma and bladder cancer) were analyzed by real time PCR2) Expression of membrane TGF-βRⅡand cytoplasim TGF-β1 in L02, MCF-7, A549, T24, ScaBER and BIU-87 were analyzed by flow cytometry (FCM)3) Expression of membrane TGF-βRⅡin L02, MCF-7, A549, T24, ScaBER and BIU-87 was analyzed by immunohistochemistry (IHC)2. Blockade of TGF-β1 signal in L02, ScaBER and T24 1) After transfection of soluble plasmid Fc:TβRⅡinto L02, ScaBER and T24, we detected the expression of Fc:TβRⅡin the culture supernatants by Western blot2) The expression of Smad2/3 in experimental cells was detected by Western blot when Si-Smad2/3 was transfected into tumor cells3. The biological effect on growth and motility of tumor cells by TGF-βRⅡ1) Experimental cells were staining by PKH-26, then 48 h proliferation index was detected by FCM2) The influence of overexpressed TGF-βRⅡon the migration and invasion of cancer cells was evaluated by Transwell assay, Cell number was counted by hematoxylin-eosin stain Group:①control;②Fc:TβRⅡ;②TGF-β1;③Si-Smad2/34. Sequence analysis of TGF-βRⅡin baldder cancer cells and tissuesFirst, designing sequence primers of TGF-βRⅡtargeting in NO.383-2086bp (coding region); Gene magnification of TGF-βRⅡwas preformed by RT-PCR; DNA product was extraction by gel extraction kit, and purified product was sent to Life Technologies (Shanghai) for sequence analysis; Using Blast in pubmed for gene sequences matching experiment5. TGF-β1/TGF-βRⅡdownstream pathways analysis in bladder cancer cells1) Phosphorylated Smads were detected by Western blot2) Interaction of TGF-βRⅡcomplex and Smad was detected by IP3) p15 and Cdc25A genes that are important to cell proliferation and CUTL1 gene relevant to motility were analyzed by real-time PCR in L02, ScaBER and T244) The biological effect was detected again by Western blot after 0 h,4 h and 8 h treatment of TGFβ1 (2 ng/ml)6. Detection of TGFβeffect on TGF-βRⅡ-mutated group (a) and non-mutated group (b) from primary cells isolated bladder cancer tissues1) Isolation primary cells from bladder cancer specimen 2) Expression of TGF-PRⅡin group a and b was detected by IHC3) Proliferation index was analysed by FCM in primary cells Group:①0;②24 h;③24 h-TGF-p 14) The influence of TGF-(3RII on the migration and invasion of primary cells was evaluated by Transwell assay Group:①Control;②TGF-β1;③Fc:TβRⅡ5) Expression of p15, Cdc25A and CUTL1 in a and b group was detected by RT-PCR after 0 h,2 h and 4 h treatment of TGFβ1[RESULTS]1) TGF-PRⅡwas overexpressed in bladder cancer cell line T24, concomitant with point mutations, especially the G→A mutation (Glu269 Lys)2) Whilst leaving Smad2/3 binding unaffected, TGF-βRII mutations resulted in the unaffected tumor cell growth and also enhanced cell mobility by TGF-β1 engagement.3) Such phenomena perhaps partially explained by the mutated TGF-βRII pathway deregulating p15 and Cdc25A genes and CUTL1 gene. On the other hand, transfecting recombinant TGF-βRII-Fc vectors or smad2/3 siRNA blocked such abnormal gene expressions.4) Clinically, such G→A mutations were also found in patients with bladder cancer and were correlated with the worse malignant phenotypes.[CONCLUSION]For the first time we detected point mutation of TGF-βRII in bladder cancer cell T24. Mutation was related to high motility of T24 cell, and such G→A mutations were also found in patients with bladder cancer and were correlated with the worse malignant phenotypes. These findings provide new insights into how TGF-β1 signaling is tailored during tumorigenesis and new information into the current TGF-β1-based therapeutic strategies, especially in bladder cancer patient treatment.