The Role Of Androgenic Metabolites Of Steroidal Aromatase Inactivators In The Treatment Of Breast Cancer

Objective: To explore the mechanism of steroidal aromatase inactivators in the treatment of breast cancer,to explain the feasibility of switching from non-steroidal aromatase inhibitors to steroidal aromatase inactivators after drug resistance to non-steroidal drugs,and to guide the practical medical decision.Methods: The effects of steroidal aromatase inactivators Formestane(4-OHA),EXE and their 17-Hydroxyl metabolite 4-hydroxytestosterone(4-OHT),17-hydroxy-exemectane(17-HEXE)on the cell proliferation in MCF-7,ZR-75-1 and MDA-MB-231 cell lines at the indicated concentrations were measured by counting cells using a Burker’s chamber,with cell viability determined by trypan blue dye exclusion.The androgenic effects of different concentrations of formestane,EXE and its 17-hydroxy metabolites,and dihydrotestosterone(DHT)were evaluated by Hershberger assay using male Wistar rats.Female Sprague Dawley rats with 7,12-dimethyl-1,2-benzanthracene(DMBA)induced tumors received ovariectomy and were randomly allocated into DHT,4-OHT,17-HEXE treatment group and placebo control group.The ratio of tumor volume to initial tumor volume before allocation was defined as the relative volume.The relative volume of tumors and the average number of tumors in different groups of SD rats were compared.All data obtained were expressed as the (?)±SEM and analyzed using one-way analysis of variance(ANOVA),followed by the LSD post hoc test for multiple comparisons(SPSS 11.5 statistical software).p< 0.05 was considered statistically significant.Results:1.In the MCF-7 cell lines,all the test drugs inhibited the proliferation of the cells,and the higher the drug concentration,the more obvious the effect of inhibition.Among them,the 17-hydroxy metabolites of AIs,i.e.4-OHT and 17-HEXE inhibited cell proliferation at any concentration stronger than their upstream compounds 4-OHA and EXE at the same concentration.In the ZR-75-1 cell lines,cell proliferation was significantly inhibited by high concentrations of reagents,while 4-OHT and 17-HEXE also exerted stronger inhibitory cells than 4-OHA and EXE.In MDA-MB-231 cell lines which is estrogen receptor(ER)negative and androgen receptor(AR)negative,there is no correlation between drug type or concentration and inhibition of cell proliferation.2.By comparing the weights of the prostate,seminal vesicle and levator ani muscles of Wistar rats,it was found that different drugs exert different degrees of androgenic and/or myotrophic potencies on castrated Wistar rats,and all showed positive correlation between the intensity of androgenicity and drug dose,and all these effects were significantly weakened when adding the androgen receptor antagonist flutamide(Flu)in combination.Among them,4-OHT and 17-HEXE showed stronger androgenic potencies than that of 4-OHA and EXE at the same concentration level.3.After 4 weeks of treatment,the of tumors in DMBA induced SD rats in 4-OHT,and 17 HEXE experimental groups were 2.5,0.3,1.7,respectively,and each of them are statistically significantly smaller than that of the control group(10.2)(P<0.05).It is worth noting that the relative volume of tumor in 4-OHT group was significantly reduced after four weeks of topical treatment.The average tumor numbers in DHT,4-OHT,17 HEXE group and control group were 2.3,1.6,2.9 and 4.3,respectively,and the difference between the each experimental group and the control group was statistically significant(p<0.05).Conclusion:1.Under the premise of ensuring exogenous estradiol(E2),steroidal AIs and their 17-hydroxy metabolites can inhibit the proliferation of AR(+)breast cancer cell lines,but not for AR(-)breast cancer cell lines.2.Steroidal AIs and their 17-hydroxy metabolites have androgenic and/or myotrophic effects on the prostate,seminal vesicle and levator ani muscle of castrated male Wistar rats.It is therefore suggested that it can function through the androgen receptor pathway in vivo.3.Direct topical application of 4-OHT and 17 HEXE ointment to local lesions can inhibit the growth of breast cancer tumors in SD rats and prevent the appearance of new tumors without blocking independent on estrogen receptor pathway.This effect is independent of endogenous estrogen levels and with high possibility due to the activation of AR.It may be one of the reasons for the replacement of steroidal AIs after the failure of non-steroidal AIs treatment.