Study On The Mechanism Of HHQ-4 Inhibiting The Proliferation Of Breast Cancer Cells Under Glucose Deprivation

Background: Although limited glucose availability often occurs in poorly vascularized solid tumors,cancer cells initiate the unfolded protein response(UPR)to support cellular homeostasis and survival under stress conditions.Objective: In view of the activation of UPR in breast cancer cells under glucose deprivation,we intend to screen new quinolone derivatives that inhibit UPR and the mechanism of their anti-proliferation effect on breast cancer cells was also studied.Methods: The stress environment induced by glucose deprivation or2-deoxy-D-glucose(2-DG)was established to study the inhibitory effect of the derivative of quinolinone,(2-hexyl-3-methyl-4(1H)-quinolinone(HHQ-4),on the proliferation of breast cancer cells(MCF-7 and MDA-MB-231).By means of gene transfection,analysis of gene activity splicing form,protein phosphorylation and expression level,etc.,we further study the effect of HHQ-4 on the transcriptional regulation pathway of UPR response key regulatory protein,glucose regulatory protein 78(glucose-regulated protein 78,GRP78),in breast cancer cells under glucose deprivation.The relationship between the regulatory effect and the anti-proliferative activity of HHQ-4 on breast cancer cells under glucose deprivation was further studied.Results: We found that HHQ-4 obviously showed selective cytotoxicity and anti-proliferative activity against glucose-deprived breast cancer cells.Interestingly,HHQ-4 had no effect under normal growth conditions.HHQ-4 also suppressed transcription from the promoter of a UPR hallmark gene,glucose-regulated protein 78(GRP78)in glucose-deprived breast cancer cells.Constitutive expression of GRP78 completely prevented breast cancer cells from HHQ-4-mediated proliferationinhibition during glucose starvation,stressing the important role of suppression of the GRP78 in HHQ-4-mediated UPR attenuation and cytotoxicity.HHQ-4 was also found to exert inhibitory activity against breast cancer cell proliferation by suppressing three survival arms of the UPR,including PERK/eIF2?/ATF4,IRE1/XBP1,and ATF6,which orchestrate an intricate signaling network to modulate GRP78 gene transcription under glucose-deprived stress.Furthermore,HHQ-4 combined with2-DG synergistically enhanced breast cancer cell proliferation inhibition in vitro.Conclusion: Our findings show HHQ-4 could be considered a promising candidate,alone or in combination with 2-DG,for selectively inhibiting breast cancer cell proliferation through down-regulating the transcription and expression of GRP78 under stressful microenvironments.