Alcohol,smoking, and risk of Her2‐overexpressing and triple‐negative breast cancer relative to estrogen receptor‐positive breast cancer

Epidemiological evidence is limited on how alcohol consumption and smoking are associated with risk of different subtypes of breast cancer, such as triple‐negative (TN) and human epidermal growth factor receptor 2‐overexpressing (H2E) breast cancers, which may have different etiologies from more common luminal (estrogen receptor [ER+]) breast cancers. In this population‐based case‐case study, we evaluated the association between alcohol, smoking, and risk of H2E and TN breast cancer, compared with ER+ breast cancers, among women aged 20–69 years. Using polytomous regression, associations between alcohol consumption, smoking, and breast cancer risk were evaluated in 909 ER+, 1,290 TN, and 489 H2E breast cancer patients, with ER+ breast cancer patients as the reference group. Current alcohol consumption at diagnosis was associated with a lower risk of H2E breast cancer (odds ratio = 0.74, 95% confidence interval: 0.58–0.92) relative to ER+ cancers. No difference in association was observed by menopausal status. No association between alcohol consumption and TN breast cancer relative to ER+ breast cancer was observed. Women who smoked did not have an altered risk of TN or H2E breast cancer, relative to ER+ cancer. Our results suggest that alcohol is associated with lower risk of H2E breast cancer relative to ER+ breast cancer. This study adds to the body of epidemiologic evidence that breast cancer etiology differs by breast cancer subtype.     

Stromal immunoglobulin κC expression is associated with initiation of breast cancer in TA2 mice and human breast cancer

The initiation of spontaneous breast cancer (SBC) in Tientsin Albino 2 (TA2) mice is related to mouse mammary tumor virus (MMTV) infection, and MMTV amplification is hormonally regulated. To explore the insertion site of MMTVLTR in TA2 mouse genome, reverse PCR and nested PCR were used to amplify the unknown sequence on both sides of the MMTV‐LTRSAG gene in SBC and normal breast tissue of TA2 mice. Furthermore, the clinicopathological significance of the insertion site was evaluated in 43 samples of normal breast tissue, 46 samples of breast cystic hyperplasia, 54 samples of ductal carcinoma in situ, 142 samples of primary breast cancer and 47 samples of lymph node metastatic breast cancer by RNA in situ hybridization. We confirmed that the insertion site of the MMTV‐LTRSAG gene was located between Ig κ v2‐112 and Ig κ v14‐111 in chromosome 6 of TA2 mouse. IG κ C was localized in the stromal cells of TA2 mouse with SBC and in human breast cancer tissues. Tumor cells were negative for IG κ C in RNA in situ hybridization. The positive staining index of IG κ C in stromal cells was the highest in lymph node metastatic breast cancer, followed by primary breast cancer, ductal carcinoma in situ, and breast cystic hyperplasia. Furthermore, the positive staining index of IG κ C was related to the expression of ER, PR, HER2 and Ki‐67. Our findings showed that stromal IG κ C expression was associated with the initiation of SBC in TA2 mice. IG κ C may be a high‐risk factor for the initiation and progression of human breast cancer.     

Prothymosin‐α enhances phosphatase and tensin homolog expression and binds with tripartite motif‐containing protein 21 to regulate Kelch‐like ECH‐associated protein 1/nuclear factor erythroid 2‐related factor 2 signaling in human bladder cancer

Prothymosin‐α (PTMA) is a small, acidic protein that is usually transported into the nucleus and involves many cellular and immunological functions. Previous studies demonstrated that aberrant location of PTMA expression exists in human bladder cancer, but the role of PTMA protein expression remains elusive. In this study, we created ectopic nuclear or cytoplasmic PTMA expression in human bladder cancer cells by infecting lentiviruses carrying wild type or deleted nuclear localization signal of the PTMA gene. The in vivo tumorigenesis assay showed PTMA protein with deleted nuclear localization signal promotes J82 xenograft tumor growth in mice and shortens their survival more so than the wild type. Chromatin immunoprecipitation showed that wild‐type PTMA protein binds to the PTEN promoter and enhances phosphatase and tensin homolog (PTEN) expression. Through immunoblot proteomics and in vivo ubiquitination studies, PTMA protein can bind with tripartite motif‐containing protein 21 (TRIM21) and block its ubiquitination. Also, TRIM21 can downregulate both forms of PTMA protein. In human bladder tumors, loss of nuclear PTMA expression was an unfavorable prognostic indicator for shorter disease‐free survival (hazard ratio, 1.54; P = 0.009). Our data support that nuclear PTMA protein serves as a tumor suppressor in bladder cancer through upregulating PTEN and orchestrating TRIM21 for the regulation of Nrf2 signaling.     

A novel approach for targeted elimination of CSPG4‐positive triple‐negative breast cancer cells using a MAP tau‐based fusion protein

Chondroitin sulfate proteoglycan 4 (CSPG4) has been identified as a highly promising target antigen for immunotherapy of triple‐negative breast cancer (TNBC). TNBC represents a highly aggressive heterogeneous group of tumors lacking expression of estrogen, progesterone and human epidermal growth factor receptor 2. TNBC is particularly prevalent among young premenopausal women. No suitable targeted therapies are currently available and therefore, novel agents for the targeted elimination of TNBC are urgently needed. Here, we present a novel cytolytic fusion protein (CFP), designated αCSPG4(scFv)‐MAP, that consists of a high affinity CSPG4‐specific single‐chain antibody fragment (scFv) genetically fused to a functionally enhanced form of the human microtubule‐associated protein (MAP) tau. Our data indicate that αCSPG4(scFv)‐MAP efficiently targets CSPG4⁺ TNBC‐derived cell lines MDA‐MB‐231 and Hs 578T and potently inhibits their growth with IC₅₀ values of ～200 nM. Treatment with αCSPG(scFv)‐MAP resulted in induction of the mitochondrial stress pathway by activation of caspase‐9 as well as endonuclease G translocation to the nucleus, while induction of the caspase‐3 apoptosis pathway was not detectable. Importantly, in vivo studies in mice bearing human breast cancer xenografts revealed efficient targeting to and accumulation of αCSPG4(scFv)‐MAP at tumor sites resulting in prominent tumor regression. Taken together, this preclinical proof of concept study confirms the potential clinical value of αCSPG4(scFv)‐MAP as a novel targeted approach for the elimination of CSPG4‐positive TNBC.     

Endocrine sensitivity of estrogen receptor‐positive breast cancer is negatively correlated with aspartate‐β‐hydroxylase expression

Although prognostic markers for early estrogen receptor (ER)‐positive breast cancer have been extensively developed, predictive markers for adjuvant endocrine therapy are still lacking. Focusing on the mechanisms underlying endocrine resistance, we investigated whether the endocrine sensitivity of ER‐positive breast cancer cells was correlated with the expression of aspartate‐β‐hydroxylase (ASPH), which is involved in the development of hepatocellular carcinoma. ASPH expression in ER‐positive and tamoxifen‐resistant breast cancer cells was upregulated by the MAPK and phosphoinositide‐3 kinase (PI3K) pathways, which both play pivotal roles in endocrine resistance. In the clinical setting, ASPH expression was negatively correlated with recurrence‐free survival of luminal B breast cancer patients that received adjuvant endocrine therapy, but not in patients that did not receive adjuvant endocrine therapy. Luminal B breast cancer is one of the intrinsic molecular subtypes identified by the Prediction Analysis of Microarray 50 (PAM50) multiple gene classifier, and because of its poor response to endocrine therapy, chemotherapy in addition to endocrine therapy is generally required after surgical resection. Our results suggest that the endocrine sensitivity of luminal B breast cancer can be assessed by examining ASPH expression, which promotes the consideration of a prospective study on the association between ASPH expression at the mRNA and protein levels in luminal B breast cancer and subsequent response to endocrine therapy.     

Depletion of DNA damage binding protein 2 sensitizes triple‐negative breast cancer cells to poly ADP‐ribose polymerase inhibition by destabilizing Rad51

Poly ADP‐ribose polymerase inhibitors (PARPi) have shown promising therapeutic efficacy in triple‐negative breast cancer (TNBC) patients. However, resistance ultimately develops, preventing a curative effect from being attained. Extensive investigations have indicated the diversity in the mechanisms underlying the PARPi sensitivity of breast cancer. In this study, we found that DNA damage binding protein 2 (DDB2), a DNA damage‐recognition factor, could protect TNBC cells from PARPi by regulating DNA double‐strand break repair through the homologous recombination pathway, whereas the depletion of DDB2 sensitizes TNBC cells to PARPi. Furthermore, we found that DDB2 was able to stabilize Rad51 by physical association and disrupting its ubiquitination pathway‐induced proteasomal degradation. These findings highlight an essential role of DDB2 in modulating homologous recombination pathway activity and suggest a promising therapeutic target for TNBC.     

ATP‐P2Y2‐β‐catenin axis promotes cell invasion in breast cancer cells

Extracellular adenosine 5′‐triphosphate (ATP), secreted by living cancer cells or released by necrotic tumor cells, plays an important role in tumor invasion and metastasis. Our previous study demonstrated that ATP treatment in vitro could promote invasion in human prostate cancer cells via P2Y2, a preferred receptor for ATP, by enhancing EMT process. However, the pro‐invasion mechanisms of ATP and P2Y2 are still poorly studied in breast cancer. In this study, we found that P2Y2 was highly expressed in breast cancer cells and associated with human breast cancer metastasis. ATP could promote the in vitro invasion of breast cancer cells and enhance the expression of β‐catenin as well as its downstream target genes CD44, c‐Myc and cyclin D1, while P2Y2 knockdown attenuated above ATP‐driven events in vitro and in vivo. Furthermore, iCRT14, a β‐catenin/TCF complex inhibitor, could also suppress ATP‐driven migration and invasion in vitro. These results suggest that ATP promoted breast cancer cell invasion via P2Y2‐β‐catenin axis. Thus blockade of the ATP‐P2Y2‐β‐catenin axis could suppress the invasive and metastatic potential of breast cancer cells and may serve as potential targets for therapeutic interventions of breast cancer.     

SHON,a novel secreted protein,regulates epithelial–mesenchymal transition through transforming growth factor‐β signaling in human breast cancer cells

The epithelial–mesenchymal transition (EMT) is one of the main mechanisms contributing to the onset of cancer metastasis, and has proven to be associated with breast cancer progression. SHON is a novel secreted hominoid‐specific protein we have previously identified; it is specifically expressed in all human cancer cell lines tested and is oncogenic for human mammary carcinoma cells. Here, we show that ectopic overexpression of SHON in immortalized human mammary epithelial cells is sufficient for cells to acquire the mesenchymal traits, as well as the enhanced cell migration and invasion, along with the epithelial stem cell properties characterized by increased CD44^high/CD24^low subpopulation and mammosphere‐forming ability. Moreover, we demonstrate that SHON positively activates the autocrine transforming growth factor‐β (TGF‐β) pathway to contribute to EMT, while SHON itself is induced by TGF‐β in mammary epithelial cells. These data are in favor of a SHON‐TGFβ‐SHON‐positive feedback loop that regulates EMT program in breast cancer progression. Finally, examination of the human clinic breast cancer specimens reveals that tumor cells may extracellularly release SHON protein to promote the cancerization of surrounding cells. Together, our findings define an important function of SHON in regulation of EMT via TGF‐β signaling, which is closely associated with the invasive subtypes of human breast cancer.     

Associations of metabolic syndrome and C‐reactive protein with mortality from total cancer,obesity‐linked cancers and breast cancer among women in NHANES III

Although metabolic syndrome (MetS) is a prognostic factor for cancer occurrence, the association of MetS and cancer mortality remains unclear. The purpose of this study was to evaluate whether MetS, components of MetS and C‐reactive protein (CRP) are associated with cancer mortality in women. A total of 400 cancer deaths, with 140 deaths from obesity‐linked‐cancers (OLCas), [breast (BCa), colorectal, pancreatic and endometrial], linked through the National Death Index, were identified from 10,104 eligible subjects aged ≥18 years. Cox proportional hazards regression was used to estimate multivariable‐adjusted hazard ratios (HR) for cancer mortality. MetS was associated with increased deaths for total cancer [HR = 1.33, 95% confidence interval (CI) 1.04–1.70] and BCa [HR = 2.1, 95% CI, 1.09–4.11]. The risk of total cancer [HR = 1.7, 95% CI, 1.12–2.68], OLCas [HR = 2.1, 95% CI, 1.00–4.37] and BCa [HR = 3.8, 95% CI, 1.34–10.91] mortality was highest for women with all MetS components abnormal, compared to those without MetS. Linear associations of blood‐pressure [HR = 2.5, 1.02–6.12, Quartile (Q) 4 vs Q1, p trend = 0.004] and blood‐glucose [HR = 2.2, 1.04–4.60, Q4 vs. Q1, p trend = 0.04] with total‐OLCas mortality were observed. A threefold increased risk of BCa mortality was observed for women with enlarged waist circumference, ≥100.9 cm, [HR = 3.5, 1.14–10.51, p trend = 0.008] and in those with increased blood glucose, ≥101 mg/dL, [HR = 3.2, 1.11–9.20, p trend = 0.03] compared to those in Q1. None of the components of MetS were associated with total‐cancer mortality. CRP was not associated with cancer mortality. In conclusion, MetS is associated with total‐cancer and breast‐cancer mortality, with waist circumference, blood pressure and blood glucose as independent predictors of OLCas and BCa mortality.     

Extracellular 5′‐nucleotidase (CD73) promotes human breast cancer cells growth through AKT/GSK‐3β/β‐catenin/cyclinD1 signaling pathway

To identify the role and to explore the mechanism of extracellular 5′‐nucleotidase (CD73) in human breast cancer growth, CD73 expression was measured firstly in breast cancer tissues and cell lines, and then interfered with or over‐expressed by recombinant lentivirus in cell lines. Impacts of CD73 on breast cancer cell proliferation and cell cycle were investigated with colony formation assay, CCK‐8 and flow cytometry. The relationship between CD73 and AKT/GSK‐3β/β‐catenin pathway was assessed with adenosine, adenosine 2A receptor antagonist (SCH‐58261), adenosine 2A receptor agonist (NECA), CD73 enzyme inhibitor (APCP) and Akt inhibitor (MK‐2206). Moreover, the effect of CD73 on breast cancer growth in vivo was examined with human breast cancer transplanting model of nude mice. The results showed that the expression of CD73 was high in breast cancer tissues and increased with advanced tumor grades and lympho‐node status. CD73 expression was higher in more malignant cells, and CD73 overexpression promoted breast cancer cell proliferation in both in vivo and in vitro. It activated AKT/GSK‐3β/β‐catenin/cyclinD1 signaling pathway through CD73 enzyme activity and other mechanism.     

Matriptase‐2 gene (TMPRSS6) variants associate with breast cancer survival,and reduced expression is related to triple‐negative breast cancer

Matriptase‐2 (TMPRSS6) has been identified as a breast cancer risk factor. Here, we examined relationships between TMPRSS6 genetic variations and breast cancer risk and survival, and determined the gene and protein expressions in breast tumors and assessed their clinical importance. Thirteen TMPRSS6 polymorphisms were genotyped in 462 invasive breast cancer cases and 458 controls. Gene expression was analyzed from 83 tumors and protein expression from 370 tumors. We then assessed the statistical significance of associations among genotypes, clinicopathological characteristics and survival. The TMPRSS6 variant rs2543519 was associated with breast cancer risk (p = 0.032). Multivariate analysis showed that four variants had effects on survival—rs2543519 (p = 0.017), rs2235324 (p = 0.038), rs14213212 (p = 0.044) and rs733655 (p = 0.021)—which were used to create a group variable that was associated with poorer prognosis correlating with more alleles related to reduced survival (p = 0.006; risk ratio, 2.375; 95% confidence interval, 1.287–4.382). Low gene expression was related to triple‐negative breast cancer (p = 0.0001), and lower protein expression was detected in undifferentiated (p = 0.019), large (p = 0.014) and ductal or lobular tumors (p = 0.036). These results confirm the association of TMRRSS6 variants with breast cancer risk and survival. Matriptase‐2 levels decrease with tumor progression, and lower gene expression is seen in poor‐prognosis‐related triple‐negative breast cancers. Our study is the first to show that matriptase‐2 gene variants are related to breast cancer prognosis, supporting matriptase‐2 involvement in tumor development.