Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in childhood. Recently, we demonstrated the overexpression of both DNA methyltransferase 3A (DNMT3A) and 3B (DNMT3B) in RMS tumour biopsies and cell lines compared to normal skeletal muscle. Radiotherapy may often fail due to the abnormal expression of some molecules able to drive resistance mechanisms. The aim of this study was to analyse the involvement of DNMT3A and DNMT3B in radioresistance in RMS. RNA interference experiments against DNMT3A/3B were performed in embryonal RMS cells, upon ionizing radiation (IR) exposure and the effects of the combined treatment on RMS cells were analysed. DNMT3A and DNMT3B knocking down increased the sensitivity of RMS cells to IR, as indicated by the drastic decrease of colony formation ability. Interestingly, DNMT3A/3B act in two different ways: DNMT3A silencing triggers the cellular senescence program by up-regulating p16 and p21, whilst DNMT3B depletion induces significant DNA damage and impairs the DNA repair machinery (ATM, DNA-PKcs and Rad51 reduction). Our findings demonstrate for the first time that DNMT3A and DNMT3B overexpression may contribute to radiotherapy failure, and their inhibition might be a promising radiosensitizing strategy, mainly in the treatment of patients with metastatic or recurrent RMS tumours.
The occurrence of cancer in newborns within the first 28 days of life is uncommon, with different clinical presentation from other age groups. Prenatal diagnosis is reported in about half of patients, while a genetic predisposition condition is supposed. The management of a newborn with cancer can be challenging and needs to be tailored according to the histology and the primary tumor site; surgery represents the main strategy, while chemotherapy should be considered with caution because of the higher toxicity and mortality due to different pharmacokinetics in neonates compared to older children. We describe the first Italian series over a 15-year period of patients affected by both benign and malignant neoplastic diseases diagnosed within the first 28 days of life; 74 newborns were diagnosed with neonatal tumors, representing 1.5% of the cancer population in the same period, and a prevalence of germ cell tumors (55%) and neuroblastoma (16%) was observed. Surgery was performed on 80% of patients, while chemotherapy was necessary for about 20% of patients. The 5-year overall survival (OS) exceeded 90%; treatment-related deaths are a major concern, representing 80% of overall deaths. A genetic/syndromic condition was detected in 16% of the population; additionally, a cancer predisposition syndrome (CPS) was identified in about 10% of patients. According to our experience, all newborns affected by cancer should warrant genetic counselling and a screening test for CPS.
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