Many of the tripartite motif (TRIM) proteins function as E3 ubiquitin ligases and are assumed to be involved in various events, including oncogenesis. In regard to tripartite motif-containing 44 (TRIM44), which is an atypical TRIM family protein lacking the RING finger domain, its pathophysiological significance in breast cancer remains unknown. We performed an immunohistochemical study of TRIM44 protein in clinical breast cancer tissues from 129 patients. The pathophysiological role of TRIM44 in breast cancer was assessed by modulating TRIM44 expression in MCF-7 and MDA-MB-231 breast cancer cells. TRIM44 strong immunoreactivity was significantly associated with nuclear grade (p = 0.033), distant disease-free survival (p = 0.031) and overall survival (p = 0.027). Multivariate analysis revealed that the TRIM44 status was an independent prognostic factor for distant disease-free survival (p = 0.005) and overall survival (p = 0.002) of patients. siRNA-mediated TRIM44 knockdown significantly decreased the proliferation of MCF-7 and MDA-MB-231 cells and inhibited the migration of MDA-MB-231 cells. Microarray analysis and qRT–PCR showed that TRIM44 knockdown upregulated CDK19 and downregulated MMP1 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 the p65 subunit of NF-κB and IκBα in both MCF-7 and MDA-MB-231 cells. TRIM44 would play a role in the progression of breast cancer by promoting cell proliferation and migration, as well as by enhancing NF-κB signaling.

Endocrine therapy is standard treatment for estrogen receptor (ER)-positive breast cancer, yet long-term treatment often causes acquired resistance, which results in recurrence and metastasis. Recent studies have revealed that RNA-binding proteins (RBP) are involved in tumorigenesis. Here, we demonstrate that PSF/SFPQ is an RBP that potentially predicts poor prognosis of patients with ER-positive breast cancer by posttranscriptionally regulating ERα (ESR1) mRNA expression. Strong PSF immunoreactivity correlated with shorter overall survival in patients with ER-positive breast cancer. PSF was predominantly expressed in a model of tamoxifen-resistant breast cancer cells, and depletion of PSF attenuated proliferation of cultured cells and xenografted tumors. PSF expression was significantly associated with estrogen signaling. PSF siRNA downregulated ESR1 mRNA by inhibiting nuclear export of the RNA. Integrative analyses of microarray and RNA immunoprecipitation sequencing also identified SCFD2, TRA2B, and ASPM as targets of PSF. Among the PSF targets, SCFD2 was a poor prognostic indicator of breast cancer and SCFD2 knockdown significantly suppressed breast cancer cell proliferation. Collectively, this study shows that PSF plays a pathophysiologic role in ER-positive breast cancer by posttranscriptionally regulating expression of its target genes such as ESR1 and SCFD2. Overall, PSF and SCFD2 could be potential diagnostic and therapeutic targets for primary and hormone-refractory breast cancers. Significance: This study defines oncogenic roles of RNA-binding protein PSF, which exhibits posttranscriptional regulation in ER-positive breast cancer.

For patients with HER2-positive breast cancer, the prognostic impact of pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) is unclear when stratified by hormonal receptor (HR) status; however, the impact of pCR on survival when stratified by hormonal receptor (HR) status is uncertain. This multicenter retrospective study investigated the predictors of pCR and its prognostic value in Japanese patients 366 HER2-positive breast cancer who received NAC. pCR was defined as no invasive residual tumor in the breast or axilla. Median follow-up was 55 months. Multivariate analysis revealed that HR status (OR, 0.37; p < 0.001) was one of the independent predictors of pCR. Five-year recurrence-free survival was higher in HR-negative patients with pCR (93%) than in those without pCR (68%), and pCR was independently prognostic (hazard ratio, 0.32; p = 0.005). However, 5-year recurrence-free survival was not different between HR-positive patients with pCR (94%) and those without pCR (84%), and pCR was not significantly prognostic (hazard ratio, 0.53; p = 0.39). In addition, 5-year overall survivals were high and similar (97% in pCR, 94% in non-pCR). Among 204 patients treated with neoadjuvant trastuzumab, pCR was not significantly prognostic in the HR-positive group (hazard ratio, 0.63; p = 0.56). Our study suggested that the HER2-positive HR-positive patients had a good prognosis despite the lower achievement rate of pCR, whose prognostic impact was smaller than that in the HER2-positive HR-negative patients. The treatment strategy for HER2-positive breast cancer can be stratified by HR status.

Recent advances in RNA studies have revealed that functional long noncoding RNAs (lncRNAs) contribute to the biology of cancers. In breast cancer, estrogen receptor α (ERα) is an essential transcription factor that primarily promotes the growth of luminal-type cancer, although only a small number of lncRNAs are identified as direct ERα targets and modulators for ERα signaling. In this study, we performed RNA-sequencing for ER-positive breast cancer cells and identified a novel estrogen-inducible antisense RNA in the COL18A1 promoter region, named breast cancer natural antisense transcript 1 (BNAT1). In clinicopathological study, BNAT1 may have clinical relevance as a potential diagnostic factor for prognoses of ER-positive breast cancer patients based on an in situ hybridization study for breast cancer specimens. siRNA-mediated BNAT1 silencing significantly inhibited the in vitro and in vivo growth of tamoxifen-resistant ER-positive breast cancer cells. Notably, BNAT1 silencing repressed cell cycle progression whereas it promoted apoptosis. Microarray analysis revealed that BNAT1 silencing in estrogen-sensitive breast cancer cells repressed estrogen signaling. We showed that BNAT1 knockdown decreased ERα expression and repressed ERα transactivation. RNA immunoprecipitation showed that BNAT1 physically binds to ERα protein. In summary, BNAT1 would play a critical role in the biology of ER-positive breast cancer by modulating ERα-dependent transcription regulation. We consider that BNAT1 could be a potential molecular target for diagnostic and therapeutic options targeting luminal-type and endocrine-resistant breast cancer.

Background: Solitary fibrous tumors (SFT) are uncommon mesenchymal neoplasms which can arise in any anatomical location. Pleural SFTs have been most frequently documented; however, breast SFT is an exceedingly rare entity and seldom present in male breast, with only 8 previously reported cases. Recently, STAT6 immunostaining was considered to be a definitive marker of SFT, however, no case of the male breast SFT showing STAT6 positivity preoperatively has been reported. Methods and Results: We describe a case of breast SFT in a 73-year-old male patient with a 12-month history of a palpable breast mass. The only associated clinical symptom was bilateral gynecomastia. An ultrasound scan examination revealed an oval, well-circumscribed and hypoechoic mass with hypervascularity. A core-needle biopsy was performed, and microscopic examination with immunohistochemistry confirmed the diagnosis of SFT. He underwent a complete surgical resection with clear margins, and there were no signs of high cellularity, remarkable mitotic activity, pleomorphism, hemorrhage or necrosis. Conclusion: A perioperative immunohistochemical evaluation for diffuse and intense nuclear expression of STAT6 was helpful to distinguish SFT from myofibroblastoma. We, herein, describe the first case of SFT in a male breast, confirmed by STAT6 immunostaining positivity. We also conducted a literature review of all previous cases of breast SFTs.