Abstract P3-07-06: TRIM44 is a possible poor prognostic factor for breast cancer patients and positively regulates NF-κB signaling pathway

[Background]

Many of the tripartite motif (TRIM) proteins, like Efp/TRIM25 which was identified by our group previously (Nature 417, 871-875, 2002), function as E3 ubiquitin ligases, and are thought to be involved in various physiological and pathological processes such as immunity and oncogenesis. In regard to tripartite motif containing 44 (TRIM44), which is an atypical TRIM family protein lacking RING finger domain, some evidences suggest that it is implicated in the progression of several human malignancies. But its pathophysiological significance in breast cancer remains unknown.

[Methods]

In the present study, immunohistochemical analysis using anti-TRIM44 antibody was performed in clinical breast cancer tissues from 129 patients with the approval of institutional ethical committees (approval number: 845). We then explored the pathophysiological role of TRIM44 in breast cancer by modulating TRIM44 expression in MCF-7 and MDA-MB-231 breast cancer cells.

[Results]

TRIM44 strong immunoreactivity was significantly associated with nuclear grade, distant disease-free survival and overall survival of the breast cancer patients. With multivariate analysis it was shown that the TRIM44 status was an independent prognostic factor for distant disease-free survival and overall survival. The proliferation of MCF-7 and MDA-MB-231 cells was significantly decreased by siRNA-mediated TRIM44 knockdown. TRIM44 knockdown also suppressed migration of MDA-MB-231 cells. Microarray analysis and qRT-PCR revealed that TRIM44 knockdown upregulated CDK19 (Cyclin Dependent Kinase 19), which is reported to be a tumor suppressor gene, whereas downregulated MMP1 (Matrix Metallopeptidase 1) in MDA-MB-231 cells. Notably, TRIM44 knockdown impaired nuclear factor-kappa B (NF-κB)-mediated transcriptional activity stimulated by tumor necrosis factor α (TNFα). Moreover, TRIM44 knockdown substantially attenuated the TNFα-dependent phosphorylation of p65 subunit of NF-κB and IκBα in both MCF-7 and MDA-MB-231 cells.

[Discussion]

Our clinical study showed that prognosis of breast cancer patients is correlated with the immunoreactivity detected by anti-TRIM44 antibody. This result suggested that expression of TRIM44 protein could be used as a potential biomarker of breast cancer. We demonstrated that NF-κB signaling pathway is modulated by TRIM44. Since NF-κB augmentation is shown to be related to aggressive character of breast cancer, stimulation of NF-κB signaling with TRIM44 might be underlying mechanism of poor prognosis. Our in vitro study showed TRIM44 knockdown caused attenuated proliferation and migration of breast cancer cells, raising the possibility of TRIM44 as a potential therapeutic target for breast cancer. These findings provide new clues to develop alternative effective strategies for breast cancer management.

Citation Format: Kawabata H, Azuma K, Ikeda K, Sugitani I, Kinowaki K, Fujii T, Osaki A, Saeki T, Horie-Inoue K, Inoue S. TRIM44 is a possible poor prognostic factor for breast cancer patients and positively regulates NF-κB signaling pathway [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-07-06.

MicroRNA-574-3p, identified by microRNA library-based functional screening, modulates tamoxifen response in breast cancer

Most primary breast cancers express estrogen receptor α and can be treated via endocrine therapy using anti-estrogens such as tamoxifen; however, acquired endocrine resistance is a critical issue. To identify tamoxifen response-related microRNAs (miRNAs) in breast cancer, MCF-7 cells infected with a lentiviral miRNA library were treated with 4-hydroxytamoxifen (OHT) or vehicle for 4 weeks, and the amounts of individual miRNA precursors that had integrated into the genome were evaluated by microarray. Compared to the vehicle-treated cells, 5 'dropout' miRNAs, which were downregulated in OHT-treated cells, and 6 'retained' miRNAs, which were upregulated in OHT-treated cells, were identified. Of the dropout miRNAs, we found that miR-574-3p expression was downregulated in clinical breast cancer tissues as compared with their paired adjacent tissues. In addition, anti-miR-574-3p reversed tamoxifen-mediated suppression of MCF-7 cell growth. Clathrin heavy chain (CLTC) was identified as a miR-574-3p target gene by in silico algorithms and luciferase reporter assay using the 3' untranslated region of CLTC mRNA. Interestingly, loss and gain of miR-574-3p function in MCF-7 cells causes CLTC to be upregulated and downregulated, respectively. These results suggest that functional screening mediated by miRNA libraries can provide new insights into the genes essential for tamoxifen response in breast cancer.

P4-01-21: An Estrogen-Inducible Transcription Factor FOXP1 Promotes Estrogen-Dependent Cell Proliferation of Breast Cancer Cells and Is Associated with 5-Year Disease-Free Survival in Patients with Tamoxifen-Treated Breast Cancer

Estrogen signaling pathways are involved in the growth and development of breast tumors through the activation of estrogen receptor a (ERα). ERα is expressed in most breast cancers and involves in estrogen-dependent proliferation by acting as transcription factors activating the expression of target genes. Various coregulators and transcription factors are associated with ERα-mediated transcriptional control of target genes. Therefore, a comprehensive understanding of estrogen signaling pathways in breast cancer is required for both treatment and diagnosis of the disease. Forkhead box P1 (FOXP1) is a member of the forkhead box transcription factor family and has been reported to be associated with various types of tumors. Here, we investigated the expression pattern of FOXP1 by immunohistochemistry in a series of 133 invasive breast cancers and compared it with clinicopathological factors. The expression of FOXP1 was detected in nuclei in 89 cases (67%) and correlated positively with tumor grade and hormone receptor status, including ERα and progesterone receptor (PgR), and negatively with pathological tumor size (pT). And in ERα-positive MCF-7 breast cancer cells, we demonstrated that FOXP1 mRNA was upregulated by estrogen and that ERα recruitment to ER binding sites within the FOXP1 gene region identified by ChIP-chip analysis was increased. We also demonstrated that proliferation of MCF-7 cells was increased by exogenously transfected FOXP1 and decreased by FOXP1-specific siRNA. Moreover, in MCF-7 cells, FOXP1 enhanced estrogen response element (ERE)-driven transcription. Finally, FOXP1 immunoreactivity was significantly more elevated in relapse-free breast cancer patients treated with tamoxifen than in relapse patients treated with it. Taken together, these results suggest that FOXP1 plays an important role in proliferation of breast cancer cells by modulating estrogen signaling and that FOXP1 immunoreactivity might be associated with the estrogen dependency of breast cancer clinically, which may predict favorable prognosis in the patients treated with tamoxifen.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-01-21.

miR-148a is an androgen-responsive microRNA that promotes LNCaP prostate cell growth by repressing its target CAND1 expression

Recent advances in cancer biology reveal that microRNAs (miRNAs) are involved in the regulation of cancer-related genes, or they function as tumor suppressors or oncogenes. In prostate cancer, evidence has accumulated for the contribution of the androgen-dependent gene network to tumor growth, although the precise functions of miRNAs in prostate cancer remain to be investigated. Here, we identified androgen-responsive miRNAs by the short RNA sequencing analysis in LNCaP prostate cancer cells. Among 10 miRNAs with known sequences, we have determined that miR-148a reduces the expression of cullin-associated and neddylation-dissociated 1 (CAND1), a negative regulator of SKP1-Cullin1-F-box (SCF) ubiquitin ligases, by binding to the 3'-untranslated region of CAND1 mRNA. CAND1 knockdown by small interfering RNA promoted the proliferation of LNCaP cells. Our study indicates the potential contribution of miR-148a to the growth of human prostate cancer.

Knockdown of Efp by DNA-modified small interfering RNA inhibits breast cancer cell proliferation and in vivo tumor growth

The estrogen-responsive gene Efp promotes the growth of breast cancer cells by stimulating the degradation of a negative cell-cycle regulator, 14-3-3sigma, and is hence considered a suitable molecular target for breast cancer therapy. The use of small interfering RNA (siRNA) and its derivatives to silence cancer-related genes is being investigated with the aim of identifying clinical applications for these molecules. Recently, it has been shown that DNA-modified siRNA (chimeric siRNA) has good potential in clinical applications, because it induces fewer off-target effects or immune responses in mammalian cells. In the present study, we identified the most specific and effective siRNA (siEfp-1) for silencing Efp expression in MCF-7 breast cancer cells. For this purpose, we used an algorithm that primarily eliminates off-target effects. siEfp-1 considerably suppressed the in vitro proliferation and cell-cycle progression of MCF-7 cells, as well as the in vivo growth of MCF-7 tumors, in athymic mice. DNA-modified siEfp-1 (chimeric siEfp) significantly inhibited the expression of Efp, proliferation of cultured cells and the in vivo growth of MCF-7-derived tumors in athymic mice. In addition, the silencing of Efp expression by siEfp-1 and chimeric siEfp increased the expression of the 14-3-3sigma protein. These results suggest that siEfp-1 and chimeric siEfp could be useful in breast cancer therapy. Chimeric siEfp, in particular, has a high specificity and induces few side effects and is therefore expected to be used as a novel nucleic acid-based therapeutic agent.

Vitamin K2 induces phosphorylation of protein kinase A and expression of novel target genes in osteoblastic cells

Vitamin K is known as a critical nutrient required for bone homeostasis and blood coagulation, and it is clinically used as a therapeutic agent for osteoporosis in Japan. Besides its enzymatic action as a cofactor of vitamin K-dependent gamma-glutamyl carboxylase (GGCX), we have previously shown that vitamin K(2) is a transcriptional regulator of bone marker genes and extracellular matrix-related genes, by activating the steroid and xenobiotic receptor (SXR). To explore a novel action of vitamin K in osteoblastic cells, we identified genes up-regulated by a vitamin K(2) isoform menaquinone-4 (MK-4) using oligonucleotide microarray analysis. Among these up-regulated genes by MK-4, growth differentiation factor 15 (GDF15) and stanniocalcin 2 (STC2) were identified as novel MK-4 target genes independent of GGCX and SXR pathways in human and mouse osteoblastic cells. The induction of GDF15 and STC2 is likely specific to MK-4, as it was not exerted by another vitamin K(2) isoform MK-7, vitamin K(1), or the MK-4 side chain structure geranylgeraniol. Investigation of the involved signaling pathways revealed that MK-4 enhanced the phosphorylation of protein kinase A (PKA), and the MK-4-dependent induction of both GDF15 and STC2 genes was reduced by the treatment with a PKA inhibitor H89 or siRNA against PKA. These results suggest that vitamin K(2) modulates its target gene expression in osteoblastic cells through the PKA-dependent mechanism, which may be distinct from the previously known vitamin K signaling pathways.

Identification of novel androgen response genes in prostate cancer cells by coupling chromatin immunoprecipitation and genomic microarray analysis

The androgen receptor (AR) plays a key role as a transcriptional factor in prostate development and carcinogenesis. Identification of androgen-regulated genes is essential to elucidate the AR pathophysiology in prostate cancer. Here, we identified androgen target genes that are directly regulated by AR in LNCaP cells, by combining chromatin immunoprecipitation (ChIP) with tiling microarrays (ChIP-chip). ChIP-enriched or control DNAs from the cells treated with R1881 were hybridized with the ENCODE array, in which a set of regions representing approximately 1% of the whole genome. We chose 10 bona fide AR-binding sites (ARBSs) (P<1e-5) and validated their significant AR recruitment ligand dependently. Eight upregulated genes by R1881 were identified in the vicinity of the ARBSs. Among the upregulated genes, we focused on UGT1A and CDH2 as AR target genes, because the ARBSs close to these genes (in UGT1A distal promoter and CDH2 intron 1) were most significantly associated with acetylated histone H3/H4, RNA polymerase II and p160 family co-activators. Luciferase reporter constructs including those two ARBSs exhibited ligand-dependent transcriptional regulator/enhancer activities. The present study would be powerful to extend our knowledge of the diversity of androgen genetic network and steroid action in prostate cancer cells.