Systemic chemotherapy-induced microsatellite instability in the mononuclear cell fraction of women with breast cancer can be reproducedin vitroand abrogated by amifostine

Abstract

Objectives Microsatellite instability (MSI) induction by alkylating agent-based chemotherapy (ACHT) may underlie both tumor resistance to chemotherapy and secondary leukaemias in cancer patients. We investigated if ACHT could induce MSI in tumor-derived plasma-circulating DNA (pfDNA) and in normal peripheral blood mononuclear (PBMN) cells. We also evaluated if amifostine could interfere with this process in an in-vitro model. Methods MSI was determined in pfDNA, PBMN cells and urine cell-free DNA (ufDNA) of 33 breast cancer patients before and after ACHT. MCF-7 cells and PBMN from normal donors were exposed in vitro to melphalan, with or without amifostine. ResultsWe observed at least one MSI event in PBMN cells, pfDNA or ufDNA of 87, 80 and 80% of patients, respectively. In vitro, melphalan induced MSI in both MCF-7 and normal PBMN cells. In PBMN cells, ACHT-induced MSI occurred together with a significant decrease in the expression of the DNA mismatch repair gene hMSH2. Amifostine decreased hMSH2 expression and also prevented MSI induction only in normal PBMN cells. Conclusions ACHT induced MSI in PBMN cells and in tumour-derived pfDNA. Because of its protective effect against ACHT induction of MSI in normal PBMN cells in vitro, amifostine may be a potential agent for preventing secondary leukaemias in patients exposed to ACHT.

Chemotherapy induces genomic instability in oral mucosal cells of women with breast cancer

“…There was no correlation between changes in MSI in the studied areas between the oral mucosal cells and biological matrices such as mononuclear peripheral blood DNA from urine sediment and plasma DNA of women with breast cancer (Figure 1) previously studied by Pinto et al [9] . Figure 1.…”

“…Previous work in our study group demonstrated induction of MSI in normal cells of the mononuclear fraction of peripheral blood DNA from urine sediment and plasma DNA of women with breast cancer undergoing chemotherapy regimen with the presence of alkylating agents [2,9] . In an in vitro model with lymphocytes exposed to alkylating agents, Marsicano and Pinto et al showed the presence of genomic instability and decrease of repair protein expression hMSH2 [9,10] .…”

“…Figure 1. Percentage of events of genomic instability in the markers in samples of oral mucosal cells (A) compared to DNA from urine sediment (B), peripheral blood mononuclear fraction (C) and plasma DNA (D) studied by Pinto et al [9]…”

“…The secondary leukemias show frequently microsatellite instability and chromosomal aberrations that proves to be an indicator of genotoxicity in the long run, given that these leukemias arise in the period from 50 to 10 years after the end of treatment [9] . These secondary leukemias are usually preceded by myelodysplastic syndromes and are characterized by significant chemoresistance to treatment which represents a worse prognosis [2,9] . Although work on the genomic instability in tumor cells is constant in papers upon the induction of genomic instability in different biological matrices are scarce in literature [2] .…”

“…Among these works, Dietmaier et al showed frequent MSI in both tumor cells from patients with HNPCC and sporadic as in non-neoplastic cells of the colonic mucosa of these patients, indicating that MSI can also occur in normal cells and should be considered in the analysis for MSI screening of the molecular HNPCC [8] . In a study of urinary sediment and plasma DNA of women with breast cancer Pinto et al demonstrated the susceptibility of these biological matrices to genomic instability after exposure to alkylating agents [9] .…”