The Nuclear Factor KappaB Activation: The Key Step Of EGF-promoted Proliferation In Estrogen-negative Breast Cancer Cells

More recently, A lot of proofs show that the signal from the family of epidermal growth factor receptor(EGFR) can prvide breast cancer autocrine signal, especially in estrogen receptor negative breast cancer. The EGFR family belongs to receptor tyrosine kinase (RTK) family. The activation of their TK domain can downstream active Ras-Raf-mitogen-activated protein kinase(MAPK) pathway, phosphatidylinositol-3(PI3)-Akt pathway and protein kinase C(PKC) pathway. We know that IkB kinase(IKK)- neuclear facter kappa B(NF-kB) system can also be activated by all above three ways and the constitutive activation of NF-kB has close link to ER negative status, poor differation, metastatisis and poor prognosis in BC. Are there some relations between EGFR family overexpression and NF-kB system continuative activation? In this study, the impact from EGF to the proliferation in ER negative BC cells, and especially the influence from NF-kB pathway activation to the signal-transmission of EGF family and the feasibility of taken IKKα as a prognosis index were reserched.1 The effect of EGF on cell-cycle in ER negative breast cancer cell line MDA-MB-435S Objective To investigate the mechanism of EGF-impacted cell-cycle inER-negative breast cancer cell line MDA-MB-435SMaterials and Methods MDA-MB-435S, a ER-negative breast cancer cell line, was choosed to perform this study. The cyclin Dl was measured by Western blot and the influence on cell-cycle was assayed by Flow cytometry (FCM). Results Cyclin Dl expression in four groups was measured by Western blot. Data show that EGF could remarkably enhanced cyclin Dl expression, 83 % more than that in control group and estrogen rised about 19% than that in control group. Tumor necrosis factor alpha (TNF-α) inhibite the cyclin Dl exprssion, 17% less than that in control group. EGF up-regulated the cyclin Dl expression in ER negative cell line MDA-MB-435S. FCM assay show phase G₀/G₁ 69.36%, phase S 22.77% and proliferation index (PI) 0.31 when adding EGF. Compared with control group, EGF rise the percentage of cells in phase S, decreas the percentage of cells in phase G₀/G₁ (p<0.05) and rise PI significantly (p<0.05) . Conclusion EGF-EGFR pathway can up-regulate the cyclin Dl expression and had stronger effect than that of E₂ - ER pathway in ER negative cell line MDA-MB-435S. EGF-EGFR pathway promote tumor cells from phase G₀/G₁ to phase S and cyclin Dl actually regulate cell-cycle on phase G₀/G₁. So EGF-EGFR pathway may promote the cell proliferation by enhancing the cyclin Dl exprssion. 2 The NF-kB activation : The key step of EGF-promoted proliferation in ER negative breast cancer cellsObjective To investigate the relationship between ER status and IKKα expression, the influence on IKKa expression from EGF-EGFR pathway and thefeasibility by using Go6976 to inhibit the effect of EGF-promoted proliferation in ER negative cell line.Materials and Methods Four breast cancer cell lines were choosed to perform this study, one ER positive cell line(MCF-7) and three ER negative cell lines (MDA-MB-435S, MDA-MB-231, SK-BR-3). For known the relation between ER status and IKKa expression, IKKa expression was measured by Western blot from four different ER status cell lines. Also the IKKa was measured by Western blot for comparing the difference between EGF and E2 .Using Western blot to test cyclin Dl and FCM to analyse the cell-cycle, Go6976 was studied to inhibit the effect of EGF-promoted proliferation in ER negative cell line MDA-MB-435S. Results Experimental result show that the order of the IKKa expression from low to high was MCF-7 , SK-BR-3, MDA-MB-231, MDA-MB-435S, about 1:1.2:1.5; 1.5. The IKKa expression in three ER negative cell lines was higher than that in ER positive cell line. The IKKa expression after treared by EGF was 18% higher than that treated by E2. In the study of the influence from EGF and Go6976 to cell-cycle, the data shown that EGF could remarkably enhanced cyclin Dl expression about 83% than control group did .In group EGF adding Go6976, the cycl...