Abstract P5-10-03: OncomiR-569 deregulate p53 pathway and initiate breast oncogenesis

Background: The 3q26.2 chromosomal loci is highly amplified in large set of breast cancers, primarily in aggressive basal tumors are difficult to treat in the clinic. Our amplicon data suggests that 3q26.2 is a large structurally complex amplicon and multiple components in the amplicon contribute to tumor initiation and progression either alone or through cooperative activity. Detailed mapping of the 3q26.2 amplicon by us demonstrated a microRNA, miR569 is highly amplified as a part of 3q26.2 amplicon in breast cancer patient's samples. The role of microRNAs amplified at 3q26 loci is not well studied and their molecular functions and targets were not well known. Thus our studies provide novel mechanism underlying miR569 oncogenesis.

Methods: Following the Institutional Review Board approval, tissues obtained from MD Anderson Cancer Center tumor bank were used to exatract DNA and RNA. Human miR-569 was cloned into pEZX-MR06 lentiviral vector used for the production of amphotropic viruses to infect the target cells. The miRIDIAN microRNA mimics were used to overexpress miRs and the antimiRs were used to knock down the miRNAs. All the transfections were performed using Oligofectamine. Trypsinized cells were grown in 5% matrigel for the 3D morphogenesis of epithelial cells.

Results: Our results demonstrated a strong correlation between 3q26.2 amplification and expression of miR569 in patient samples of breast cancer. We subsequently demonstrated that overexpression and knockdown of miR569 in the breast epithelial cells altered their growth, proliferation, and lumen filling in 3-dimensional cultures grown in Matrigel. Importantly ectopic expression of miR569 in breast epithelial cells promoted tumor growth and increased metastatic potential in mouse xenograft models. Seed match based analysis of the microRNA targets, in silico studies and in vitro experiments showed that miR-569 directly target Tumor protein 53-induced nuclear protein1 (TP53INP1) and inhibited the expression of a tumor suppressor gene TP53INP1 expression. Loss of TP53INP1 expression mediated by miR569 altered normal cell growth cycle and subsequently promoted the survival and growth of tumor cells. Our in vitro results showed that knockdown of miR-569 and subsequent increase in TP53INP1 expression enhanced the sensitivity of cancer cell lines to cisplatin. Our immunohistochemical analysis showed that TP53INP1 protein levels were higher in normal tissues compared to cancer tissues. Further, reduced expression of TP53INP1 was observed in invasive cancers as compared to low malignant potential tumors, and decreased TP53INP1 protein levels were associated with worsened outcomes in breast cancer patients.

Disscussion: TP53INP1 had previously been identified as a combined target of p53 and p73; however our studies indicate that miR-569 regulates TP53INP1 levels independently of p53 and p73 expression. Based on our preclinical results of antimiR-569 on cell survival, tumor growth and cisplatin sensitivity, inhibiting miR-569 activity or increasing TP53INP1 expression may be valid therapeutic approaches to treat breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-10-03.

HER2-Associated Breast Cancer Signature Using a 3D Culture Model

Background: Carcinomas of the breast account for one third of all cancers occurring in woman and responsible for approximately one quarter of cancer-related deaths in females. The HER2/Neu -oncogene is amplified in 20-25% percent of human primary breast cancers and this alteration is associated with disease behaviour. Whereas signalling pathways emanating from HER2 have been characterized, much less is known about the transcriptionally regulated genes that contribute to HER2 tumorigenic effects.Materials and Methods: Normal and HER2 overexpressing mammary epithelial cells (MCF10A) were grown in extracellular matrix to form 3D structures, which allow epithelial cells to organize into structures that resemble their in vivo architecture. RNA was isolated from the 3D structures and hybridized to an Affymetrix HuGene 1.0 ST oligonucleotide array.Results: Upon HER2 overexpression, mammary epithelial cells lost their polarity and formed disorganized structures in matrigel. Using microarrays we analyzed transcriptional events responsible for the morphological changes and found that several sets of genes such as integral proteins, transcription factors, matrix proteases and chemokines were highly altered in the HER2 overexpressing group. Using gene annotation we defined molecular-pathways which are highly altered in HER2 overexpressing cells. More generally, our study proposes a mechanistic description of the processes underlying the HER2 transcriptional network.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4146.