The transcriptional coactivator Amplified in Breast Cancer 1 (AIB1) plays a major role in the progression of hormone and HER2-dependent breast cancers but its role in triple negative breast cancer (TNBC) is undefined.
Amplified in breast cancer 1 (AIB1) is a candidate oncogene in human breast cancer, which has been identified to be amplified and overexpressed in several types of other human cancers.
Given the amplified expression of SRC-3 in breast cancers, the objective of this study was to determine how increasing SRC-3 protein levels are regulated in MCF-7 breast cancer cells.
Although it was found that AIB1 could be phosphorylated by some kinases including PI3K, the function of AIB1 and AKT interaction in breast cancer is not well defined.
PFKFB4 and phosphorylated SRC-3 levels are increased and correlate in oestrogen receptor-positive tumours, whereas, in patients with the basal subtype, PFKFB4 and SRC-3 drive a common protein signature that correlates with the poor survival of patients with breast cancer.
Furthermore, <i>in vivo</i> syngeneic tumor studies revealed that PELP1 knockdown resulted in increased survival of tumor-bearing mice as compared with mice injected with control cells.<b>Implications:</b> These data demonstrate that cytoplasmic PELP1/AIB1-containing complexes function to promote advanced cancer phenotypes, including outgrowth of stem-like cells, associated with estrogen-independent breast cancer progression.<i></i>.
AIB1 was analyzed with immunohistochemistry in tissue microarrays of the Danish subcohort (N = 1396) of the International Breast Cancer Study Group's trial BIG 1-98 (randomization between adjuvant tamoxifen versus letrozole versus the sequence of the two drugs).
In addition to finding previously well-known drivers, the identified modules pointed to other novel findings such as the interaction between NCOR2 and NCOA3 in breast cancer.
We show that HER2 signaling promotes breast cancer cell proliferation through regulation of E2F1-driven DNA metabolism and replication genes together with phosphorylation and activity of the transcriptional coactivator SRC-3.
Progestin and antiprogestin responsiveness in breast cancer is driven by the PRA/PRB ratio via AIB1 or SMRT recruitment to the CCND1 and MYC promoters.
AIB1 reduction in MCFDCIS cells was correlated with significant reduction in the CD24-/CD44+ breast cancer-initiating cell (BCIC) population, and a decrease in myoepithelial progenitor cells in the DCIS lesions in vitro and in vivo.
ANCO1 can also repress other E2-responsive genes, indicating that AIB1, AIB1-Δ4 and ANCO1 are important determinants of endocrine and growth factor responsiveness in breast cancer.
In patients with high AIB1 expression (>75%), there was a significant decrease in recurrence rate (HR 0.40, 95% CI 0.26-0.61, P < 0.001) and breast cancer mortality rate (HR 0.38, 95% CI 0.21-0.69, P = 0.0015) with tamoxifen treatment.
As the members of the p160/nuclear receptor co-activator (NCOA) family, NCOA1, NCOA2 and NCOA3 are known to be overexpressed in breast cancer and essentially involved in estrogen-mediated cancer cell proliferation we asked if these proteins are involved in the ERα-mediated transactivation of PLAC1 in breast cancer cells.
We recently demonstrated that the E3 ubiquitin ligase adaptor speckle-type poxvirus and zinc finger (POZ) domain protein (SPOP) interacts directly with SRC-3 and promotes its cullin 3-dependent ubiquitination and proteolysis in breast cancer, thus functioning as a potential tumor suppressor.
Studies were included in the meta-analysis if they met all the predetermined criteria, such as: (a) case-control or cohort studies; (b) the primary outcome was clearly defined as BC; (c) the exposure of interest measured was AIB1 polyglutamine repeat length genotype; (d) provided relative risk (RR) or odds ratio (OR) estimates and their 95% confidence intervals (CIs).