| Breast cancer is a common malignant tumor.The incidence of breast cancer accounts for 25% of all cancer cases and about 15% of female cancer deaths.In the US statistics for 2017,approximately 252,710 women were diagnosed with breast cancer,including 40,610 deaths.Breast cancer poses a great threat to the health and lives of women around the world.Therefore,the molecular mechanism of the occurrence,metastasis and recurrence of breast cancer has become a hot topic in clinical and basic research.HRD1 is an E3 ubiquitin ligase involved in endoplasmic reticulum-associated degradation.It degrades misfolded proteins during embryogenesis and rheumatoid arthritis,and plays a role in promoting the degradation of proteins.Our previous study found that HRD1 can degrade IGF-1R by ubiquitin-proteasome pathway and reverse EMT of breast cancer cells,thus inhibiting the migration and proliferation of breast cancer cells.In order to further study the molecular mechanism of HRD1 against breast cancer,we screened and analyzed the possible degradation substrates of HRD1.Mass spectrometry analysis revealed that LDHB may be one of the substrates for HRD1 degradation.Abnormal energy metabolism is an important feature of tumor cells,even if the tumor cells in the premise of adequate oxygen is still glycolytic lactic acid in the form of energy metabolism.LDHB,a key enzyme for glycolysis,is highly expressed in a variety of tumors.We hypothesize that whether HRD1 can inhibit the development of breast cancer by degrading LDHB to improve cell energy metabolism.First,we selected 6paired breast cancer samples.,Western Blot results showed that HRD1 was lowly expressed in cancer tissues,and LDHB was High expression in cancer tissues.Moreover,the expression of LDHB in both breast cancer cell lines was higher than that of normal breast epithelial cells,whereas the expression of HRD1 was the opposite.After overexpression of HRD1 in two breast cancer cell lines,the protein expression of LDHB decreased,and the proliferation and migration of breast cancer cells were inhibited.We passed the cycloheximide tracer experiment and ubiquitination degradation experiment,and confirmed that HRD1 is degraded by ubiquitin proteasome pathway.We then found that after overexpression of HRD1 in breast cancer cell lines,both glucose uptake and lactate production by tumor cells were inhibited,and ATP production was also suppressed.Finally,in the nude mice tumorigenesis experiment,the tumorigenicity of breast cancer cells overexpressing HRD1 was significantly lower than that of untreated breast cancer cells.These results show that HRD1 can degrade LDHB through ubiquitin proteasome pathway,inhibit the glycolysis rate of breast cancer cells,and ultimately inhibit the proliferation of breast cancer cells. |
