Placental Kisspeptins Differentially Modulate Vital Parameters of Estrogen Receptor-Positive and -Negative Breast Cancer Cells

Placental Galectins in Cancer: Why We Should Pay More Attention

The first studies suggesting that abnormal expression of galectins is associated with cancer were published more than 30 years ago. Today, the role of galectins in cancer is relatively well established. We know that galectins play an active role in many types of cancer by regulating cell growth, conferring cell death resistance, or inducing local and systemic immunosuppression, allowing tumor cells to escape the host immune response. However, most of these studies have focused on very few galectins, most notably galectin-1 and galectin-3, and more recently, galectin-7 and galectin-9. Whether other galectins play a role in cancer remains unclear. This is particularly true for placental galectins, a subgroup that includes galectin-13, -14, and -16. The role of these galectins in placental development has been well described, and excellent reviews on their role during pregnancy have been published. At first sight, it was considered unlikely that placental galectins were involved in cancer. Yet, placentation and cancer progression share several cellular and molecular features, including cell invasion, immune tolerance and vascular remodeling. The development of new research tools and the concomitant increase in database repositories for high throughput gene expression data of normal and cancer tissues provide a new opportunity to examine the potential involvement of placental galectins in cancer. In this review, we discuss the possible roles of placental galectins in cancer progression and why they should be considered in cancer studies. We also address challenges associated with developing novel research tools to investigate their protumorigenic functions and design highly specific therapeutic drugs.

Lack of Oestrogen Receptor Expression in Breast Cancer Cells Does Not Correlate with Kisspeptin Signalling and Migration

Kisspeptin is an anti-metastatic mediator in many cancer types, acting through its receptor, KISS1R. However, controversy remains regarding its role in breast cancer since both pro- and anti-metastatic roles have been ascribed to it. In KISS1R overexpressing triple-negative breast cancer (TNBC) cells, stimulation has been associated with increased invasion and MMP-9 expression, leading to the suggestion that hormone receptor status determines the metastatic effects of kisspeptin. To assess the veracity of this claim, we compared endogenous KISS1R signalling and physiological output in the hormone receptor-negative MDA-MB-231 and BT-20 cell lines after KP-10 (shortest active kisspeptin peptide) stimulation. MDA-MB-231 cells are metastatic when implanted in mice while BT-20 are not and remain epithelial-like. We show that both cell lines express KISS1R mRNA and respond to KP-10 by elevating calcium mobilisation. However, KP-10 stimulation induced migration of MDA-MB-231, but not BT-20 cells, in a calcium-dependent manner. Moreover, only BT-20 cells responded to KP-10 by increasing ERK phosphorylation in a β-arrestin-dependent manner. Interestingly, both cell lines displayed different complements of β-arrestin 1 and 2 expression. Overall, our data shows that, in TNBC, it is not universally true that kisspeptin/KISS1R stimulate migration or pro-metastatic behaviour, as divergent responses were observed in the two TNBC lines tested. Whether this divergence is related to the observed differences in β-arrestin complements warrants further investigation and may enable further stratification of the ability of kisspeptin to influence breast tumour behaviour.

Expression profiling of RTL1 in human breast cancer tissues and cell lines

Breast cancer (BC) is the most common cancer in females. In this regard, the identification of molecular alterations driving BC is an immediate need for developing effective immunotherapeutic tools. Here we investigated the expression of a placenta-specific protein, Retrotransposon-like 1 (RTL1) in a series of BC tissues and cell lines. RTL1-specific polyclonal antibody was generated and characterized. Using tissue microarray immunohistochemistry, expression of RTL1 in a total of 147 BC and 36 non-malignant breast tissues was investigated and the association of patient's clinicopathological parameters with RTL1 expression was then examined. Expression of RTL1 in four BC cells was assessed by flow cytometry, immunofluorescent staining and Western blotting. We observed a mixture pattern of nuclear and cytoplasmic RTL1 expression in most tissues examined, however nuclear expression was found to be dominant pattern of expression. The level of nuclear RTL1 expression was significantly higher in BC tissues (P < 0.001). A statistically significant association between nuclear RTL1 expression and histological grade and vascular invasion was found (P < 0.001 and P < 0.05). All cell lines expressed RTL1 with varying degrees at their surface. The most invasive BC cell line MDA-MB-231, compared to T-47D, SKBR3 and MCF7 expressed higher levels of RTL1 at their surface. Cells with a low level of surface expression, expressed high levels of intracellular RTL1 expression. Our antibody reacted with a specific band of about 125 KD in normal human placenta and all cell lines examined. In contrast to placenta, two additional bands were also observed in cancer cell lines. Our results showed for the first time that RTL1 is differentially expressed in BC compared to non-malignant breast tissues and is associated with a higher grade and vascular invasion. In BC cells with high metastatic and invasive potential, this antigen is mostly confined to cell surface compartment indicating the possibility of using antibody-based immunotherapy for advanced metastatic BC patients.

G protein-coupled kisspeptin receptor induces metabolic reprograming and tumorigenesis in estrogen receptor-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly metastatic and deadly disease. TNBC tumors lack estrogen receptor (ERα), progesterone receptor (PR), and HER2 (ErbB2) and exhibit increased glutamine metabolism, a requirement for tumor growth. The G protein-coupled kisspeptin receptor (KISS1R) is highly expressed in patient TNBC tumors and promotes malignant transformation of breast epithelial cells. This study found that TNBC patients displayed elevated plasma kisspeptin levels compared with healthy subjects. It also provides the first evidence that in addition to promoting tumor growth and metastasis in vivo, KISS1R-induced glutamine dependence of tumors. In addition, tracer-based metabolomics analyses revealed that KISS1R promoted glutaminolysis and nucleotide biosynthesis by increasing c-Myc and glutaminase levels, key regulators of glutamine metabolism. Overall, this study establishes KISS1R as a novel regulator of TNBC metabolism and metastasis, suggesting that targeting KISS1R could have therapeutic potential in the treatment of TNBC.

Evaluation of the combinatorial effect of Tinospora cordifolia and Zingiber officinale on human breast cancer cells

The present study was aimed to investigate the anticancer potential of the combination treatment of Tinospora cordifolia (TC) and Zingiber officinale (ZO) using network pharmacology approach. In silico analysis of the anticancer activity of TC + ZO was carried out using Cytoscape 3.2.0 software to elucidate the mechanism. The MTT assay confirms the combination of TC and ZO is more active (IC₅₀; 2 μg ml^-1) as compared to TC (509 μg ml^-1) and ZO (1 mg ml^-1) alone in MCF-7 cells. The TC + ZO combination treatment inhibits DNA synthesis, migration, and induces apoptosis in MCF-7 cells as compared to TC and ZO alone at a concentration of 1 µg ml^-1. TC + ZO combination treatment arrested cell cycle significantly at the G₀/G₁ phase. The proposed synergistic activity of the two herbs in the treatment of several cancers was correlated with an appropriate associated target/s, based on the pharmacological network. Interestingly, when both the plants used in combination, were found to regulate a total of 16 genes in 27 types of cancers. Further, ALOX5, MMP2, and MMP9 genes were identified as major targets which are responsible for the TC + ZO anticancer activity. According to merged and sub-networks of source-bioactive, bioactive-target, target-disease of TC, ZO alone and their combination; MMP9 was selected for validation purpose. The real-time PCR analysis confirmed that the TC + ZO combination treatment significantly down-regulated MMP9 mRNA expression by fivefold via up-regulation of its downstream target ER-α by 3.5-fold. In conclusion, the network analysis and in vitro validation confirmed the potent synergistic activity of TC + ZO combination treatment in breast cancer.

Vaccination with human amniotic epithelial cells confer effective protection in a murine model of Colon adenocarcinoma

As a prophylactic cancer vaccine, human amniotic membrane epithelial cells (hAECs) conferred effective protection in a murine model of colon cancer. The immunized mice mounted strong cross-protective CTL and antibody responses. Tumor burden was significantly reduced in tumor-bearing mice after immunization with hAECs. Placental cancer immunotherapy could be a promising approach for primary prevention of cancer. In spite of being the star of therapeutic strategies for cancer treatment, the results of immunotherapeutic approaches are still far from expectations. In this regard, primary prevention of cancer using prophylactic cancer vaccines has gained considerable attention. The immunologic similarities between cancer development and placentation have helped researchers to unravel molecular mechanisms responsible for carcinogenesis and to take advantage of stem cells from reproductive organs to elicit robust anti-cancer immune responses. Here, we showed that vaccination of mice with human amniotic membrane epithelial cells (hAECs) conferred effective protection against colon cancer and led to expansion of systemic and splenic cytotoxic T cell population and induction of cross-protective cytotoxic responses against tumor cells. Vaccinated mice mounted tumor-specific Th1 responses and produced cross-reactive antibodies against cell surface markers of cancer cells. Tumor burden was also significantly reduced in tumor-bearing mice immunized with hAECs. Our findings pave the way for potential future application of hAECs as an effective prophylactic cancer vaccine.

G protein-coupled KISS1 receptor is overexpressed in triple negative breast cancer and promotes drug resistance

Triple-negative breast cancer (TNBC) lacks the expression of estrogen receptor α, progesterone receptor and human epidermal growth factor receptor 2 (HER2). TNBC patients lack targeted therapies, as they fail to respond to endocrine and anti-HER2 therapy. Prognosis for this aggressive cancer subtype is poor and survival is limited due to the development of resistance to available chemotherapies and resultant metastases. The mechanisms regulating tumor resistance are poorly understood. Here we demonstrate that the G protein-coupled kisspeptin receptor (KISS1R) promotes drug resistance in TNBC cells. KISS1R binds kisspeptins, peptide products of the KISS1 gene and in numerous cancers, this signaling pathway plays anti-metastatic roles. However, in TNBC, KISS1R promotes tumor invasion. We show that KISS1 and KISS1R mRNA and KISS1R protein are upregulated in TNBC tumors, compared to normal breast tissue. KISS1R signaling promotes drug resistance by increasing the expression of efflux drug transporter, breast cancer resistance protein (BCRP) and by inducing the activity and transcription of the receptor tyrosine kinase, AXL. BCRP and AXL transcripts are elevated in TNBC tumors, compared to normal breast, and TNBC tumors expressing KISS1R also express AXL and BCRP. Thus, KISS1R represents a potentially novel therapeutic target to restore drug sensitivity in TNBC patients.