Few reports contribute insights regarding predictors of outcomes or treatment targets applicable to women aged over 40 years with lymph node-positive primary breast cancer studied here. The 55% probability of recurrence associated with positive lymph nodes after surgery emphasizes the importance of developing more effective biomarkers [17]. Here we show, for the first time to our knowledge, that 16 genes encoding proteins with diverse functions and 73 genes encoding olfactory receptors may serve as biomarkers of the recurrence of breast cancer with the ER + phenotype accompanied by lymph nodes metastasis before surgery.
Diverse human tissues express olfactory receptors that contribute to physiological processes such as cell migration, proliferation and secretion and serve as biomarkers for carcinomas of the prostate, lung, small intestine and breast [18]. Olfactory receptor family 51 subfamily E member 2 (OR51E2) serves as a biomarker for prostate cancer. OR51E2 is also called prostate-specific G-protein-coupled receptor (PSGR), because it is upregulated in prostate cancer [19, 20]. OR51E1, which is a paralog of OR51E2, serves as a potential biomarker for small intestine neuroendocrine carcinomas [21] and certain types of lung cancer [22]. Moreover, 111 olfactory receptors are detectable in testis, including specific expression of olfactory receptor family 4 subfamily N member 4 (OR4N4), and several other olfactory receptors are expressed in Epstein–Barr virus-transfected lymphocytes [23]. The present study is the first, to our knowledge, to report a correlation between the expression of olfactory receptor genes (73 gene set) and tumor recurrence of ER + breast patients with breast cancer with lymph nodes metastasis. This discovery suggests that olfactory receptors may serve as predictors of recurrence of ER + breast cancer, particularly subsequent to lymph node metastasis.
ASPH is highly expressed during fetal development and in placental trophoblasts, but not in healthy adult human tissues. Furthermore, ASPH is specifically upregulated in cancer cells and is overexpressed in more than 20 different solid neoplasms, in which it contributes to the malignant phenotype. Moreover, ASPH is associated with increased cell proliferation, invasiveness, and poor prognosis. Metastasis is a major cause of death of patients with cancer, and new antimetastatic strategies are required. Numerous pathways contribute to cell migration and invasion of normal tissues by malignant tumors. ASPH is a key player in the malignant transformation of solid tumors through enhancing cell proliferation, migration, and invasion. Furthermore, ASPH promotes tumor growth through stimulation of angiogenesis and immunosuppression. These effects are mainly achieved via the activation of the Notch and SRC signaling pathways. ASPH expression is upregulated by growth factors and hypoxia in different human tumors, and its inactivation may have broad clinical effects. Moreover, ASPH expression is silenced in normal adult breast tissue, upregulated in malignancies in situ, and highly expressed in invasive ductal carcinoma [24].
Here we show that higher differential expression of ASPH correlated with tumor recurrence in ER + patients with breast cancer, including those treated with tamoxifen. These findings indicate that ASPH will serve as a predictor of recurrent triple-negative breast cancer or the HER2-amplified subtype as well as the ER + luminal A or B subtype. Thus, the pathway mediated by ASPH might not be affected by tamoxifen.
Tumor cells employ diverse oncogenically and environmentally driven metabolic pathways to satisfy the bioenergetics and biosynthetic requirements of rapid and sustained growth of tumor cells [25]. Glutamine supports the survival of cancers through its catalytic conversion to glutamate by glutaminase (GLS) in mitochondria [26, 27]. Glutamate and its metabolites further contribute to rate-limiting cellular metabolic pathways such as the tricarboxylic acid (TCA) cycle, redox, and amino acid synthesis. The survival of triple-negative primary breast cancers and the cognate breast cancer-derived cell lines in vitro is associated with differentially elevated levels of GLS mRNA that support high glutamine utilization and increased dependence on exogenous glutamine [28]. Here we show that higher differential expression of GLS correlated with tumor recurrence in ER + patients with breast cancer, including those treated with tamoxifen. These findings indicate that GLS will serve as a biomarker of recurrence of triple-negative breast cancer as well as the ER + luminal A or B subtype. GLS may therefore represent a target of therapy designed to prevent cancer relapse, particularly after lymph nodes metastasis.
The predictive value of our gene expression profile with respect to breast cancer recurrence could be confirmed in larger number of lymph-bide-positive patients or verified in protein level. It might be a new direction that a large number of the same type of receptors as targets, rather than a single target, to develop drugs.