Inhibition of matrix metalloproteinase-2 enhances radiosensitivity by abrogating radiation-induced FoxM1-mediated G2/M arrest in A549 lung cancer cells

Effects of irradiation on tumor cell survival, invasion and angiogenesis

Ionizing irradiation is a widely applied therapeutic method for the majority of solid malignant neoplasms, including brain tumors where, depending on localization, this might often be the only feasible primary intervention.Without doubt, it has been proved to be a fundamental tool available in the battlefield against cancer, offering a clear survival benefit in most cases. However, numerous studies have associated tumor irradiation with enhanced aggressive phenotype of the remaining cancer cells. A cell population manages to survive after the exposure, either because it receives sublethal doses and/or because it successfully utilizes the repair mechanisms. The biology of irradiated cells is altered leading to up-regulation of genes that favor cell survival, invasion and angiogenesis. In addition, hypoxia within the tumor mass limits the cytotoxicity of irradiation, whereas irradiation itself may worsen hypoxic conditions, which also contribute to the generation of resistant cells. Activation of cell surface receptors, such as the epidermal growth factor receptor, utilization of signaling pathways, and over-expression of cytokines, proteases and growth factors, for example the matrix metalloproteinases and vascular endothelial growth factor, protect tumor and non-tumor cells from apoptosis, increase their ability to invade to adjacent or distant areas, and trigger angiogenesis. This review will try to unfold the various molecular events and interactions that control tumor cell survival, invasion and angiogenesis and which are elicited or influenced by irradiation of the tumor mass, and to emphasize the importance of combining irradiation therapy with molecular targeting.

New pyrazolo-[3,4-d]-pyrimidine derivative Src kinase inhibitors lead to cell cycle arrest and tumor growth reduction of human medulloblastoma cells

Medulloblastoma is the most common malignant brain tumor in children, and despite improvements in the overall survival rate, it still lacks an effective treatment. Src plays an important role in cancer, and recently high Src activity was documented in medulloblastoma. In this report, we examined the effects of novel pyrazolo-[3,4-d]-pyrimidine derivative Src inhibitors in medulloblastoma. By MTS assay, we showed that the pyrimidine derivatives indicated as S7, S29, and SI163 greatly reduce the growth rate of medulloblastoma cells by inhibiting Src phosphorylation, compared with HT22 non-neoplastic nerve cells. These compounds also halt cells in the G(2)/M phase, and this effect likely occurs through the regulation of cdc2 and CDC25C phosphorylation, as shown by Western blot. Moreover, the exposure to pyrimidine derivatives induces apoptosis, assayed by the supravital propidium iodide assay, through modulation of the apoptotic proteins Bax and Bcl2, and inhibits tumor growth in vivo in a mouse model. Notably, S7, S29, and SI163 show major inhibitory effects on medulloblastoma cell growth compared with the chemotherapeutic agents cisplatin and etoposide. In conclusion, our results suggest that S7, S29, and SI163 could be novel attractive candidates for the treatment of medulloblastoma or tumors characterized by high Src activity.

Forkhead box M1 transcription factor: a novel target for cancer therapy

FoxM1 signaling has been reported to be associated with carcinogenesis. Therefore, the FoxM1 may represent a novel therapeutic target, and thus the development of agents that will target FoxM1 is likely to have significant therapeutic impact on human cancer. This review describes the mechanisms of signal transduction associated with FoxM1 and provides emerging evidence in support of its role in the carcinogenesis. Further, we summarize data on several FoxM1 inhibitors especially "chemopreventive agents" and these agents could be useful for targeted inactivation of FoxM1, which indeed could become a novel approach for the prevention and/or treatment of human cancer.

FoxM1 down-regulation leads to inhibition of proliferation, migration and invasion of breast cancer cells through the modulation of extra-cellular matrix degrading factors

Forkhead box M1 (FoxM1) transcription factor is known to play important role in human cancers which, in part, is mediated by its ability to modulate cell cycle regulatory proteins as well as genes involved in cell proliferation and differentiation. In breast cancer, FoxM1 down-regulation is increasingly being recognized as an important mechanism for the targeted activity of anti-cancer agents. However, the mechanistic insight in support of the role of FoxM1 in aggressive breast cancer is poorly understood. We have tested the biological consequence of FoxM1 down-regulation and up-regulation in breast cancer cell lines and found that the down-regulation of FoxM1 in MDA-MB-231 and SUM149 cells by siRNA approach inhibited cell growth, clonogenicity, migration, and invasion. We also found decreased expression of CDK2 and E2F1 with concomitant increase in p21 and p27 proteins, suggesting an important role of FoxM1 in cell cycle progression. In contrast, over-expression of FoxM1 by cDNA transfection, in breast cancer cells (SUM102 and SKBR3) expressing low levels of FoxM1, resulted in increased cell proliferation, migration, and invasion. Moreover, down-regulation of FoxM1 inhibited the expression of many factors that are involved in the degradation of extra cellular matrix and angiogenesis such as uPA, uPAR, MMP-2, MMP-9, and vascular endothelial growth factor (VEGF) as well as inhibited the activity of MMP-9 and VEGF. Interestingly, over-expression of uPA by cDNA transfection abrogated the cellular effects that were observed by the down-regulation of FoxM1. Taken together, these results suggest the potential application of FoxM1 down-regulation as a novel approach for the treatment of aggressive breast cancer.