A study of HMGA1 tumorigenic role in MYCN-amplified neuroblastoma cells after radiotherapy

Abstract

Neuroblastoma is mainly a childhood tumor. It is the first malignancy affecting children under the age of five, and the third most common childhood malignancy. Neuroblastoma (NB) originates from the immature developing cells of the sympathetic nervous system. Of the utmost importance is the MYCN risk factor. MYCN amplification (MNA) in neuroblastoma is by itself associated with a high risk advanced stage disease and therapy resistance. High MYCN expression is a feature of embryonic and stem cells that is shared by MNA neuroblastoma cancers. This relates to the Cancer Stem-like Cells (CSCs) theory initiated after noticing many similarities between stem cells and a minority of cancerous cells in a heterogeneous tumor. MYCN is partly linked to neuroblastoma stemness and radioresistance could be a result. This work is based on Stable isotope labeling by amino acids in cell culture (SILAC) preliminary proteomic screening results of the MYCN amplified IMR-32 and non-MYCN amplified SK-N-SH neuroblastoma cell lines before and after radiotherapy. Irradiation induced an overexpression of N-MYC and HMGA1 in IMR-32 cell line. N-MYC and HMGA1, the active transcriptional factors, cooperate in neuroblastoma to inhibit apoptosis before irradiation while their associated role after irradiation is still uncovered. In this project, we aim to investigate the tumorigenic role of HMGA1 in IMR-32 cells compared to SK-N-SH cells on the malignant behavior of neuroblastoma after irradiation. Therefore, HMGA1 was silenced in IMR-32 and SK-N-SH cells then migration and invasion were assessed. After that cells were subjected to a high dose of ionizing radiations (2.5 Gray) before viability and proliferation assays were conducted with and without adding HMGA1 siRNAs. Without radiotherapy, HMGA1 normal expression increased significantly (P < 0.01) the wound healing in IMR-32 cells in the first six hours. Neuroblastoma is mainly a childhood tumor. It is the first malignancy affecting children under the age of five, and the third most common childhood malignancy. Neuroblastoma (NB) originates from the immature developing cells of the sympathetic nervous system. Of the utmost importance is the MYCN risk factor. MYCN amplification (MNA) in neuroblastoma is by itself associated with a high risk advanced stage disease and therapy resistance. High MYCN expression is a feature of embryonic and stem cells that is shared by MNA neuroblastoma cancers. This relates to the Cancer Stem-like Cells (CSCs) theory initiated after noticing many similarities between stem cells and a minority of cancerous cells in a heterogeneous tumor. MYCN is partly linked to neuroblastoma stemness and radioresistance could be a result. This work is based on Stable isotope labeling by amino acids in cell culture (SILAC) preliminary proteomic screening results of the MYCN amplified IMR-32 and non-MYCN amplified SK-N-SH neuroblastoma cell lines before and after radiotherapy. Irradiation induced an overexpression of N-MYC and HMGA1 in IMR-32 cell line. N-MYC and HMGA1, the active transcriptional factors, cooperate in neuroblastoma to inhibit apoptosis before irradiation while their associated role after irradiation is still uncovered. In this project, we aim to investigate the tumorigenic role of HMGA1 in IMR-32 cells compared to SK-N-SH cells on the malignant behavior of neuroblastoma after irradiation. Therefore, HMGA1 was silenced in IMR-32 and SK-N-SH cells then migration and invasion were assessed. After that cells were subjected to a high dose of ionizing radiations (2.5 Gray) before viability and proliferation assays were conducted with and without adding HMGA1 siRNAs. Without radiotherapy, HMGA1 normal expression increased significantly (P < 0.01) the wound healing in IMR-32 cells in the first six hours. Compared to SK-N-SH cells, IMR-32 cells are significantly (P < 0.05) more migratory under N-M.