Repair of DNA interstrand crosslinks as a mechanism of clinical resistance to melphalan in multiple myeloma

Abstract

Melphalan is widely used as a preparative agent in patients with multiple myeloma (MM) undergoing autologous stem cell transplantation (SCT). Although disease relapse is the major cause of death after a melphalan-conditioned autograft, the mechanism remains unclear. Melphalan produces a number of DNA adducts with the DNA interstrand crosslink (ICL) considered to be the critical cytotoxic lesion. By using a modification of the single-cell gel electrophoresis (Comet) assay, we have measured formation and repair of DNA ICL in plasma cells from melphalannaive and melphalan-treated patients (ie, those who have relapsed after a melphalan-conditioned autologous SCT or oral melphalan therapy). Similar levels of dosedependent DNA interstand crosslinking were observed in cells from both melphalan-naive and -treated patients. However, marked differences in ICL repair were observed: cells from naive patients showed no repair, whereas those from treated patients exhibited between 42% and 100% repair at 40 hours. In vitro sensitivity to melphalan in plasma cells was found to correlate with ICL repair. These findings suggest that ICL repair may be an important mechanism by which melphalan resistance emerges after autologous SCT or oral therapy. This mechanism may have implications for MM patients undergoing melphalan therapy. (Blood. 2002;100:224-229)

Enhanced repair of DNA interstrand crosslinking in ovarian cancer cells from patients following treatment with platinum-based chemotherapy

“…This can be used to measure crosslinking in lymphocytes or solid tumour material where samples are taken following treatment of patients with drugs such as ifosfamide , treosulfan (Corrie et al, 2005) or antibody directed enzyme pro-drug therapy (Webley et al, 2001). Alternatively, it can be used to measure crosslink formation and repair in cells isolated from patients and treated ex vivo with drug as in the present study, or as previously demonstrated in myeloma plasma cells treated with melphalan (Spanswick et al, 2002). In the latter study, myeloma cells from chemotherapy naïve patients were all incapable of repairing melphalan-induced crosslinks at 24 h after the peak of formation.…”

“…We have previously demonstrated that a modification of the single cell gel electrophoresis (comet) assay can be used successfully in the clinical setting to detect and quantify the levels of ICLs in patient lymphocytes and tumour cells at pharmacologically relevant doses of bifunctional alkylating agents Webley et al, 2001;Spanswick et al, 2002;Corrie et al, 2005). The method has also been used to measure cisplatin-induced ICLs in vitro (De Silva et al, 2002).…”

Involvement of the HER2 pathway in repair of DNA damage produced by chemotherapeutic agents

“…It is now increasingly used to monitor ICL formation and unhooking in clinical samples (30,40) as a pharmacodynamic end point in clinical trials (41,42), and following ex vivo treatment (39,43).…”

Phase I trial combining gemcitabine and treosulfan in advanced cutaneous and uveal melanoma patients

“…The Comet assay allows measurement of DNA damage at a single-cell level. It has been modified to allow the sensitive detection and quantitation of DNA interstrand crosslinking and can be applied to both preclinical and clinical situations (Hartley et al, 1999a(Hartley et al, , b, 2004Spanswick et al, 2002). Comet assay results could only be obtained from a limited number of patients treated in this clinical study.…”