Comprehensive immunohistochemical analysis of RET, BCAR1, and BCAR3 expression in patients with Luminal A and B breast cancer subtypes.

PURPOSE: Breast cancer (BC) is considered a heterogeneous disease composed of distinct subtypes with diverse clinical outcomes. Luminal subtype tumors have the best prognosis, and patients benefit from endocrine therapy. However, resistance to endocrine therapies in BC is an obstacle to successful treatment, and novel biomarkers are needed to understand and overcome this mechanism. The RET, BCAR1, and BCAR3 genes may be associated with BC progression and endocrine resistance. METHODS: Aiming to evaluate the expression profile and prognostic value of RET, BCAR1, and BCAR3, we performed immunohistochemistry on tissue microarrays (TMAs) containing a cohort of 361 Luminal subtype BC. RESULTS: Low expression levels of these three proteins were predominantly observed. BCAR1 expression was correlated with nuclear grade (p = 0.057), and BCAR3 expression was correlated with lymph node status (p = 0.011) and response to hormonal therapy (p = 0.021). Further, low expression of either BCAR1 or BCAR3 was significantly associated with poor prognosis (p = 0.005; p = 0.042). Pairwise analysis showed that patients with tumors with low BCAR1/low BCAR3 expression had a poorer overall survival (p = 0.013), and the low BCAR3 expression had the worst prognosis with RET high expression stratifying these patients into two different groups. Regarding the response to hormonal therapy, non-responder patients presented lower expression of RET in comparison to the responder group (p = 0.035). Additionally, the low BCAR1 expression patients had poorer outcomes than BCAR1 high (p = 0.015). CONCLUSION: Our findings suggest RET, BCAR1, and BCAR3 as potential candidate markers for endocrine therapy resistance in Luminal BC.

JDP1 (DNAJC12/Hsp40) expression in breast cancer and its association with estrogen receptor status.

The members of the DnaJ/Hsp40 proteins are highly conserved through evolution, expressed in several tissues and act as co-chaperone regulating protein folding, transport, translational initiation and gene expression. Recently, using cDNA microarray we identified differences in the expression of the JDP1 (DNAJC12) gene, a member of the DnaJ/Hsp40 family, between ER-positive and ER-negative breast tumours. In this study, using quantitative real-time PCR (qPCR) we evaluated the expression pattern of the JDP1 gene in a series of 72 primary breast tumours and investigated the effects of 17beta-estradiol on the expression of the JDP1 in MCF-7 breast cancer cells. Three patterns of JDP1 mRNA expression were identified in the primary breast tumours analysed: normal expression was found in 14% of the cases, under-expression in 50%, and over-expression in 36% of the cases. High levels of JDP1 mRNA expression were significantly associated with estrogen receptor-positive status (p=0.02). No relationship was found between JDP1 mRNA expression and any other clinicopathological characteristics of the patients. Sequence analysis of the promoter region of the JDP1 gene revealed the presence of potential estrogen response elements (EREs), suggesting it to be under the control of estrogen action. We also assessed the effects of 17beta-estradiol (10 nM) on JDP1 mRNA expression in MCF-7 breast cancer cells. The JDP1 transcripts were found to be up-regulated in a time-dependent fashion in MCF-7 cells exposed to 17beta-estradiol treatment. Here we show for the first time that JDP1 is a estrogen target gene and that its expression might be used as a marker of the ER transactivation activity and may have a predictive value for response to hormonal therapy.

Differentially expressed genes and estrogen receptor status in breast cancer.

There is a large and increasing body of experimental and clinical data supporting the involvement of estrogen on the proliferation of hormone-dependent breast tumors. Estrogen acts via its receptor (ER) stimulating cellular proliferation. ER and progesterone receptor (PR), which is regulated by estrogen via ER, have been used as prognostic markers in the clinical management of breast cancer patients. The aim of the present study was the identification of tumor-associated genes differentially expressed in breast tumors regarding the presence or absence of ER and PR. Using the technique of differential display reverse transcriptase-polymerase chain reaction (DDRT-PCR) we have isolated and cloned 127 cDNA fragments that showed differential expression in either ER+/PR+ or ER-/PR- breast tumors. Sequencing analysis of these clones revealed that 119 cDNAs had homology with known sequences in the National Center of Biotechnology Information (NCBI) and 8 were novel, showing no homology to known genes. Among these differentially expressed transcripts are metabolic enzymes, ribosomal proteins, transcription factors, hypothetical proteins, cell cycle regulators, cytoskelectum related genes, cell adhesion and motility genes. Differences in gene expression profiles are likely to explain the phenotypic differences between hormone-responsive and hormone-unresponsive breast tumors.