Low expression of Beclin 1 and elevated expression of HIF-1α refine distant metastasis risk and predict poor prognosis of ER-positive, HER2-negative breast cancer

Abstract

Even though ER-positive, HER2-negative breast tumors represent a subset of breast cancers with a better clinical outcome, approximately 12.7 % of patients in this subgroup ultimately develop cancer-related mortality. Recent studies had confirmed that hypoxia-induced autophagy-related gene Beclin 1 expression might be important for disease progression and be correlated with patient outcome in several tumors. Here, we examined the autophagic Beclin 1 and hypoxic HIF-1α levels in 378 ER-positive, HER2-negative breast cancer patients by immunohistochemistry using tissue microarray. We found that Beclin 1 was highly expressed in normal mammary gland epithelia. In contrast, it was either not expressed or only moderately expressed in 78.0 % of breast adenocarcinoma tissue. Compared to the subset overexpressing Beclin 1, the subset in which Beclin 1 levels were reduced had a poor 5-year overall survival rate (OS, 85.1 % vs. 94.1 %, P = 0.005) and a poor distant metastasis-free survival (DMFS, 79.1 % vs. 89.3 %, P = 0.037). Cox multivariate analysis confirmed that Beclin 1 was indeed an independent prognostic factor for OS and DMFS. Additionally, Beclin 1 positively correlated with HIF-1α expression (r = 0.206, P < 0.001). Importantly, among patients with HIF-1α overexpression, low levels of Beclin 1 predicted a worse OS. Our study confirmed that deficiency of Beclin 1 was a negative prognostic factor for OS and DMFS in ER-positive, HER2-negative breast cancer. The combination of Beclin 1 and HIF-1α refined the risk definition of the patient subset and provided a novel way to identify those with a high risk of relapse.

The potential of Beclin 1 as a therapeutic target for the treatment of breast cancer

“…Embryogenesis is impaired in BECN -/-mice and mice do not survive; as a result BECN +/-mice are more likely to develop Wnt1-driven mammary carcinogenesis [59]. In an immunohistochemical study involving 378 ER-positive and epidermal growth factor receptor 2 (HER-2)-negative breast cancer patients, higher Beclin 1 expression was reported in the normal mammary gland epithelium compared with breast cancer epithelium [84]. In a study regarding 20 pairs of sporadic invasive ductal carcinoma (IDC) tissues and adjacent normal tissues, Beclin 1 mRNA and protein was decreased in 70% of the IDC tissues [28], and this was in agreement with findings in preclinical animal models.…”

“…In immunohistochemical studies performed using a tissue microarray, the expression rate of Beclin 1 in breast cancer tissues was reported to be 42.4% in 125 IDC cases [85], 48.7% in 119 IDC cases of TNBC subtype [86], 44.9% in ER-negative IDC cases [87], 78.0% in 378 ER-positive, HER-2 negative IDC cases [84], 39.9% in ABT-737, EB1089, and gossypol are molecules that targets BH3 domain. Beclin 1 inhibitors include molecules such as spautin-1, 3-methyladenine, wortmannin, and LY294002, and all of these molecules are targeting PI3KCIII/Vps34.…”

“…In addition, the expression of Beclin 1 and its impact on the clinical outcome differs according to the molecular subtype of breast cancer. In a study involving 378 cases of ER-positive, HER-2 negative breast cancer, low expression of Beclin 1 was reported as an independent poor prognostic factor [84]. In a study of 114 invasive lobular carcinoma (ILC) and 692 IDC cases, Beclin 1 expression was higher in IDC compared with ILC [93], and the authors suggested this results from the differences in proliferative activity between IDC and ILC.…”

Autophagy and cancer

“…Most of these studies are correlative; nevertheless, autophagy gene mRNA and/or protein expression changes and mutations were observed in different tumor series. (Iqbal et al, 2009;Kang et al, 2009;An et al, 2011;Plantinga et al, 2014;Rao et al, 2014;Rothe et al, 2014) BECN1 (Atg6) Reduced expression in breast cancers, nonsmall cell lung cancers, renal clear cell carcinomas, brain tumors, cervical squamous cell carcinomas, hepatocellular carcinomas, ovarian cancers, osteosarcomas, melanomas, and glioblastomas Mutations in ovarian cancers, human breast cancers, prostate cancers Reduced expression due to gene methylation in breast cancers Increased expression in CD34(+) chronic myeloid leukemia cells, colon cancers (stage IIIB), non-Hodgkin lymphomas, cholangiocarcinomas (Russell et al, 1990;Futreal et al, 1992;Cliby et al, 1993;Saito et al, 1993;Tangir et al, 1996;Aita et al, 1999;Liang et al, 1999;Qu et al, 2003;Wang et al, 2006;Lee et al, 2007;Miracco et al, 2007 ;Ding et al, 2008;Liu et al, 2008;Shen et al, 2008 ;Li et al, 2009;Zhang et al, 2009;Huang JJ et al, 2010;Huang X et al, 2010;Koukourakis et al, 2010;Lazova et al, 2010;Miracco et al, 2010;Nicotra et al, 2010;Dong et al, 2011;Liu et al, 2011;Sivridis et al, 2011;Jiang et al, 2012;Choi et al, 2013;Deng et al, 2013;Dong et al, 2013;Laddha et al...…”

“…Furthermore, in an overlapping tumor series, analysis by immunohistochemistry revealed a significant decrease in BECN1 protein levels in 18 of 32 breast carcinoma cells compared with normal breast lobular of ductal epithelial cells . In line with these results, expression of BECN1 was reported to be reduced in breast cancers, nonsmall cell lung cancers, renal clear cell carcinomas, brain tumors, cervical squamous cell carcinomas, hepatocellular carcinomas, ovarian cancers, osteosarcomas, melanomas, and glioblastomas (Russell et al, 1990;Futreal et al, 1992;Cliby et al, 1993;Saito et al, 1993;Tangir et al, 1996;Aita et al, 1999;Liang et al, 1999;Qu et al, 2003;Wang et al, 2006;Lee et al, 2007;Miracco et al, 2007;Ding et al, 2008;Liu et al, 2008;Shen et al, 2008;Li et al, 2009;Zhang et al, 2009;Huang JJ et al, 2010;Huang X et al, 2010;Koukourakis et al, 2010;Lazova et al, 2010;Miracco et al, 2010;Nicotra et al, 2010;Dong et al, 2011;Liu et al, 2011;Sivridis et al, 2011;Jiang et al, 2012;Choi et al, 2013;Deng et al, 2013;Dong et al, 2013;Laddha et al, 2014;Rothe et al, 2014).…”