Novel Mechanisms In Tumor Malignant Progression And The Regulation By Small Molecule

Cancer is a major public health problem for human.Although multipule hallmarks have been identified in tumor cells,none of the oncogenes or tumor suppressor genes is thought to be deregulated in stand-alone events.The metastasis and relapse of malignant tumors still puzzled human.It makes sense to study the deep mechanism about tumor malignant progression and find the potential key molecule in the regulation of tumor metastasis or induction of differentiation.In this paper,we make research by comparative study.By comparing homologous tumor cells with different malignant degree,we found several key molecule in the regulation of tumor malignant progression and tried to make regulations upon such mechanism by small molecule compouds.The first chapter reviewed the understanding about tumor malignant progression in the present days.Several key molecules were introduced in detail for their important role during the malignant progression.In the end,we discussed about the existing anti-metastasis drugs and prospected about the future anti-tumor drugs.In the second chapter,we compared a series of melanoma cells with growing malignancy.Base on the growing levels of PRL-3 and the translocation of NHERF1 during the malignant progression of melanoma cells,we studied the regulation of NHERF1 by PRL-3 in promoting the malignant progression of melanoma.Firstly,we built a series of melanoma cells with gradually growing malignancy and validated the growing levels of PRL-3 during the malignant progression.Then,we verified that PRL-3 promoted the lymphatic metastasis in an foot pad metastasis model by animal imaging system.During the consideration about the subcellular localization of NHERF1 and its regulation on AKT signaling pathway,we came to a conclusion as following.During the malignant progression of melanoma,NHERF1 was translocated from the nucleus to the cytoplasm gradually following by the translocation of PTEN from the nucleus to the cytoplasm.For that the phosphorylation of AKT mainly took place in the nucleus of melanoma cells,the decrease of PTEN in the nucleus resulted in the increase of p-AKT which contributed for the malignant progresion of melanoma.In the end,we studied the regulation of NHERF1 by PRL-3.We found that the phosphorylation of NHERF1(Ser)kept in a relative low level in the higher malignant melanoma cells,but high level in the lower malignant melanoma cells.The phosphorylated form of NHERF1 mainly distributed in the nucleus.At the same time,NHERFI presented mainly in dephosphorylated form in the cytoplasm.PRL-3 associated with NHERF1 in the nucleus and regulated the dephosphorylation of NHERF1 at Ser site.As a result,NHERF1 was translocated from the nucleus which process was prormoted by PRL-3.In the third chapter,we compared the human mammary epithelium cells MCF-10A with three kinds of invasive breast cancer cells MCF-7,MDA-MB-231 and 4T1.We found that the expression level of PRL-3 in MCF-10A was lower than breast cancer cells(BCC).Nature product RA-V can selectively kill BCCs while the inhibitory effects on normal mammary cells are minor.Here,we make efforts to study the killing mechanisms of RA-V in the malignant breast cancer cells.Firstly,we found that RA-V inhibited the expression of PRL-3 and inhibited the adhesion,migration and invasion ability of BCCs.Then,the apoptosis was studied in RA-V induced cell death.Results showed that RA-V induced the apoptosis of BCCs in a time-and dose-dependent manner.Further study showed that RA-V-induced apoptosis was mediated by the mitochondrial pathway,not the death-recepter or ER-stress pathway.For that AKT signaling can be regulated by PRL-3 as discussed in the last chapter,we detected the phosphorylation levels of AKT upon RA-V treatment.Data showed that RA-V disrupted the interaction between PDK1 and AKT following by the inhibition of p-AKT(Thr308).Moreover,RA-V dramatically inhibited the phosphorylation of p-AKT(Ser473)and PDK1.Furthermore,RA-V-induced apoptosis could be enhanced by phosphatidylinositol 3-kinase inhibitor or attenuated by over-expression of AKT in all the three kinds of breast cancer cells.In the last chapter,we compared a pair of liposarcoma cells with PTEN deletion and further revealed another important molecule,which promotes the tumor malignant progression in differentiation-resistant conditions but not PRL-3 mediated metastasis.Firstly,we determined the inhibitory effects of SBF-1 in liposarcoma cells.Results showed that SBF-1 induced apoptosis and inhibited p-AKT.The key point was that cells of lower malignancy are more sensitive to SBF-1 than cells of higher malignancy.Although the level of PRL-3 in SW872 cells was much lower than in SW872-S cells,SBF-1 didn't inhibit the expression of PRL-3.Then,we confirmed OSBP as a target of SBF-1 by three different methods.In the end,we found that OSBP expressed more in higher malignant tumor cells,and OSBP promoted the tumor growth both in vitro and in vivo.The tumor growth regulated by SBF-1 might be mediated through OSBP.Taken together,by comparing the malignant progression and its regulation by small molecule compounds of three kinds of tumors,this paper studies the key regulator during tumor metastasis and differentiation-resistance.We reveal the underlying mechanisms of the malignant progression promoted by PRL-3 for the first time,and introduce the anti-tumor mechanisms of RA-V,which is found to inhibit the expression of PRL-3.In addition,we illustrate the anti-tumor mechanisms of small molecule SBF-1,which shows higher selectivity for higher malignant tumor cells.OSBP,one of the targets of SBF-1,shows an important role in promoting tumor malignant progression.Commonness and individuality of different kinds of tumors during the malignant progression suggest that anti-cancer therapy should be taken in a multiple manner.It makes sense to find small molecule compounds with unique activity for prventing tumor cells from malignant progression.