The anticancer effects of Metformin in the male germ tumor SEM-1 cell line are mediated by HMGA1

Abstract

IntroductionGerm cell tumors (GCTs) are the most common type of cancer in young men. These tumors usually originate from the testis, but they can occasionally develop from extragonadal sites probably due to primordial germ cells (PGCs) migration errors. Cisplatin-based chemotherapy is usually effective for male GCTs, but the risk of toxicity is high and new therapeutic strategies are needed. Although Metformin (Met) has been widely studied as a potential cancer treatment over the past decades, there is limited evidence to support its use in treating male GCTs. Additionally, the mechanism by which it acts on tumor cells is still not entirely understood.MethodsSEM-1 cells, a newly established human cell line of extragonadal origin, were treated with Met. Cell viability was studied by MTT assay, while cell migration and invasion were studied by the wound healing assay and the transwell assay, respectively. The effect of Met on 3D spheroid formation was determined by seeding SEM-1 cells in appropriate cell suspension culture conditions, and cell cycle was characterized by flow cytometry. Factors involved in PGCs migration and GCT invasion, such as IGFBP1, IGF1R, MMP-11 and c-Kit, together with cyclin D1 (a key regulator of cell cycle progression), and the upstream factor, HMGA1, were determined by immunoblots.ResultsTreatment of SEM-1 cells with Met resulted in a potent and dose-dependent reduction of cell proliferation, as evidenced by decreased nuclear abundance of cyclin D1 and cell cycle arrest in G1 phase. Also, Met prevented the formation of 3D spheroids, and blocked cell migration and invasion by reducing the expression of IGFBP1, IGF1R and MMP-11. Both, IGFBP1 and MMP-11 are under control of HMGA1, a chromatin-associated protein that is involved in the regulation of important oncogenic, metabolic and embryological processes. Intriguingly, an early reduction in the nuclear abundance of HMGA1 occurred in SEM-1 cells treated with Met.ConclusionsOur results document the antiproliferative and antimigratory effects of Met in SEM-1 cells, providing new insights into the potential treatments for male GCTs. The anticancer properties of Met in SEM-1 cells are likely related to its ability to interfere with HMGA1 and downstream targets, including cyclin D1, the IGFs system, and MMP-11.

Metformin in Gestational Diabetes Mellitus: To Use or Not to Use, That Is the Question

“…Very recently, some research groups, including ours, have highlighted a direct modulatory role of metformin in nuclear events that regulate the function of transcription factors and chromatin-remodeling proteins [51,52]. These include the hypoxia-inducible factor 1α (HIF-1α), which is known to modulate the transcription of hypoxia-related genes relevant to inflammation [53], and the high-mobility group A1 (HMGA1) chromatin-remodeling protein [54], which is involved in a variety of metabolic, embryological, and oncological processes [55][56][57]. Exposure to metformin (either at pharmacological or supra-pharmacological concentrations) has been shown to downregulate the nuclear HMGA1 protein in male germ tumor and hepatoma cell lines, leading to reduced cell viability, cell migration and proliferation [54].…”

“…These include the hypoxia-inducible factor 1α (HIF-1α), which is known to modulate the transcription of hypoxia-related genes relevant to inflammation [ 53 ], and the high-mobility group A1 (HMGA1) chromatin-remodeling protein [ 54 ], which is involved in a variety of metabolic, embryological, and oncological processes [ 55 , 56 , 57 ]. Exposure to metformin (either at pharmacological or supra-pharmacological concentrations) has been shown to downregulate the nuclear HMGA1 protein in male germ tumor and hepatoma cell lines, leading to reduced cell viability, cell migration and proliferation [ 54 ]. Whether these effects of metformin can be observed in non-tumor cells is yet unknown.…”

“…However, fetal progenitor cells and cancer cells share some similarities, including the hyperactivation of HIF-1α and HMGA1-related biological pathways [ 58 , 59 ]. This has led us to speculate that in utero exposure to metformin, causing molecular interferences with these nuclear factors, might be detrimental for normal fetal development [ 54 ].…”

“…Additionally, it is not clear if the results of preclinical studies in mice can be translated to male humans. Recently, we showed that male germ tumor cells of human origin are highly sensitive to the antiproliferative and antimigratory effects of metformin, because of the drug interferences with the expression and function of the nuclear factor HMGA1 [ 54 ], whose loss causes major histological and functional testis modifications in knock-out animals [ 107 ]. There is a general consensus that male germ cell tumors are caused by embryonic primordial germ cells migrating abnormally to the gonad during the development and are thus considered to be developmental disorders [ 108 ].…”

“…There is a general consensus that male germ cell tumors are caused by embryonic primordial germ cells migrating abnormally to the gonad during the development and are thus considered to be developmental disorders [ 108 ]. If the migrating primordial germ cells do not properly reach the gonad during this process, it could also lead to impaired male fertility, as the pool of germ cells available for adult spermatogenesis would be reduced [ 54 , 108 ]. As no experiments have been conducted to date in normal, non-malignant progenitor germ cells, we cannot be sure how the antiproliferative HMGA1-mediated effect of metformin could be similar to that observed in tumor cells [ 54 ].…”