Intratumoral estrogen production and actions in luminal A type invasive lobular and ductal carcinomas

Potential role of Fbxo22 in resistance to endocrine therapy in breast cancer with invasive lobular carcinoma

BACKGROUND

Invasive lobular carcinoma (ILC) is distinct from invasive ductal carcinoma (IDC) in terms of their hormonal microenvironments that may require different therapeutic strategies. We previously reported that selective estrogen receptor modulator (SERM) function requires F-box protein 22 (Fbxo22). Here, we investigated the role of Fbxo22 as a potential biomarker contributing to the resistance to endocrine therapy in ILC.

METHODS

A total of 302 breast cancer (BC) patients including 150 ILC were recruited in the study. Fbxo22 expression and clinical information were analyzed to elucidate whether Fbxo22 negativity could be a prognostic factor or there were any correlations among clinical variables and SERM efficacy.

RESULTS

Fbxo22 negativity was significantly higher in ILC compared with IDC (58.0% vs. 27.0%, P < 0.001) and higher in postmenopausal patients than premenopausal patients (64.1% vs. 48.2%, P = 0.041). In the ILC cohort, Fbxo22-negative patients had poorer overall survival (OS) than Fbxo22-positive patients, with 10-year OS rates of 77.4% vs. 93.6% (P = 0.055). All patients treated with SERMs, Fbxo22 negativity resulted in a poorer outcome, with 10-year OS rates of 81.3% vs. 92.3% (P = 0.032). In multivariate analysis regarding recurrence-free survival (RFS) in ILC patients, Fbxo22 status was independently predictive of survival as well as lymph node metastasis.

CONCLUSION

Fbxo22 negativity significantly impacts on survival in BC patients with IDC and ILC, and the disadvantage was enhanced among ILC postmenopausal women or patients treated with SERMs. The findings suggest that different therapeutic strategies might be needed according to the different histopathological types when considering adjuvant endocrine therapy.

PCP4/PEP19 upregulates aromatase gene expression via CYP19A1 promoter I.1 in human breast cancer SK-BR-3 cells

The Purkinje cell protein 4/peptide 19 (PCP4/PEP19) is a novel breast cancer cell expressing peptide, originally found in the neural cells as an anti-apoptotic factor, could inhibit cell apoptosis and enhance cell migration and invasion in human breast cancer cell lines. The expression of PCP4/PEP19 is induced by estrogens in estrogen receptor-positive (ER⁺) MCF-7 cells but also highly expressed in ER^- SK-BR-3 cells. In this study, we investigated the effects of PCP4/PEP19 on aromatase gene expression in MCF-7 and SK-BR-3 human breast cancer cells. In SK-BR-3 cells but not in MCF-7 cells, PCP4/PEP19 knockdown by siRNA silencing decreased the aromatase expression in gene transcriptional level. When PCP4/PEP19 was overexpressed by CMV promoter-driven PCP4/PEP19 expressing plasmid transfection, aromatase gene transcription increased in SK-BR-3 cells. This aromatase gene transcription is mainly mediated through promoter region PI.1, which is usually active in the placental tissue but not in the breast cancer tissue. These results indicate a new function of PCP4/PEP19 that would enhance aromatase gene upregulation to supply estrogens in heterogeneous cancer microenvironment.

In breast cancer subtypes steroid sulfatase (STS) is associated with less aggressive tumour characteristics

BACKGROUND

The majority of breast cancer cases are steroid dependent neoplasms, with hormonal manipulation of either CYP19/aromatase or oestrogen receptor alpha axis being the most common therapy. Alternate pathways of steroid actions are documented, but their interconnections and correlations to BC subtypes and clinical outcome could be further explored.

METHODS

We evaluated selected steroid receptors (Androgen Receptor, Oestrogen Receptor alpha and Beta, Glucocorticoid Receptor) and oestrogen pathways (steroid sulfatase (STS), 17β-hydroxysteroid dehydrogenase 2 (17βHSD2) and aromatase) in a cohort of 139 BC cases from Norway. Using logistic and cox regression analysis, we examined interactions between these and clinical outcomes such as distant metastasis, local relapse and survival.

RESULTS

Our principal finding is an impact of STS expression on the risk for distant metastasis (p<0.001) and local relapses (p <0.001), HER2 subtype (p<0.015), and survival (p<0.001). The suggestion of a beneficial effect of alternative oestrogen synthesis pathways was strengthened by inverted, but non-significant findings for 17βHSD2.

CONCLUSIONS

Increased intratumoural metabolism of oestrogens through STS is associated with significantly lower incidence of relapse and/or distant metastasis and correspondingly improved prognosis. The enrichment of STS in the HER2 overexpressing subtype is intriguing, especially given the possible role of HER-2 over-expression in endocrine resistance.

Exemestane and Its Active Metabolite 17-Hydroexemestane Induce UDP-Glucuronosyltransferase (UGT) 2B17 Expression in Breast Cancer Cells

Exemestane (EXE) is an aromatase inhibitor indicated for endocrine therapy of breast cancer in postmenopausal women. The primary active metabolite of EXE, 17-hydroexemestane (17-HE), is inactivated via glucuronidation, mainly by UDP-glucuronosyltransferase 2B17 (UGT2B17). UGT2B17 also has a primary role in inactivation of endogenous androgens testosterone and dihydrotestosterone and may play an important role in regulation of breast and prostate tumor intracrinology. We recently reported that UGT2B17 could be induced by both estrogenic and androgenic ligands in breast cancer cells via binding of the estrogen receptor α (ERα) or the androgen receptor (AR) to a complex regulatory unit in the proximal UGT2B17 promoter. In this study we show that both EXE and 17-HE increase UGT2B17 mRNA levels in breast cancer MCF-7 and MDA-MB-453 cells, and increase glucuronidation of UGT2B17 substrates, including 17-HE and androsterone. Using antagonists of ERα and AR as well as inhibition mediated by small interfering RNA (siRNA) we demonstrate that EXE and 17-HE induce UGT2B17 expression primarily via the AR. This result is consistent with previous reports that 17-HE can act as an AR ligand. In vitro studies suggest that multiple steroid-responsive DNA elements within the proximal promoter are involved in the response to 17-HE-liganded AR. The up-regulation of UGT2B17 by EXE and 17-HE in breast cancer cells might enhance the local metabolism of 17-HE as well as that of endogenous androgens, hence impacting potentially on treatment outcomes.