Synergistic effects of combination with fludarabine and carboplatin depend on fludarabine-mediated inhibition of enhanced nucleotide excision repair in leukemia

Abstract

Overcoming drug resistance remains a major obstacle to curing relapsed or refractory lymphoma and obtaining a beneficial long-term prognosis for patients, despite the introduction of several salvage regimens to date. Our ultimate purpose is to establish a standard second-line salvage chemotherapy regimen for curing relapsed/refractory lymphoma. In this basic pre-clinical study, we evaluated a combination regimen consisting of 9-β-D: -arabinofuranosyl-2-fluoroadenine (F-araA) and carboplatin that targeted nucleotide excision repair (NER) of DNA in five representative leukemia lineages in vitro. Isobologram analysis demonstrated that simultaneous exposure to these two drugs produced synergistic interactions in U937 and K562 cells, in which lines showed enhanced NER activity by the measurement of UV or drug-induced DNA strand break (comet assay), or quantitation of ERCC1 mRNA (RT-PCR), a key enzyme for NER. Histone γH2AX formation was synergistically induced, but no such formation was observed after exposure to either agent alone in K562 cells. In summary, we synergistically inhibited the NER activity of leukemia cells by treating them with a combination of F-araA and carboplatin, suggesting that this combinatory regimen could be used as a novel salvage therapy for refractory or drug-resistant lymphoma.

Palladium and Platinum Complexes of the Antimetabolite Fludarabine with Vastly Enhanced Selectivity for Tumour over Non-Malignant Cells

“…The neutral trans-[(fludarabine-H)Br(PPh 3 ) 2 ]M complexes 3 (a: M = Pd; b: M = Pt) were synthesised in two steps following general protocols, with one additional reaction affording the corresponding cationic N-heterocyclic carbene (NHC) complexes 4 (Scheme 1) [23]. The complexes were characterised by 1 H, 13 C, 19 Complexes 3 were protonated with 2,6-lutidine triflate at the N-7 atom as the most basic position, yielding the cationic complexes 4 in 88%. Using a stronger acid, e.g., HBF4 • Et2O, led to decomposition of the complexes.…”

“…For 13 C-NMR spectra, the resonance signal of the carbon atom of CD 3 CN (δ = 118.3 ppm), DMSO-d 6 (δ = 39.5 ppm) or CD 2 Cl 2 (δ = 53.8 ppm) was used [23]. The 1 H-NMR spectra were measured at 500 MHz, 13 C-NMR spectra at 125 MHz, 19 F-NMR spectra at 470 MHz, 31 P-NMR spectra at 202 MHz, and 195 Pt-NMR spectra at 107 MHz. For signal multiplicities, the following abbreviations were used: s = singlet, d = doublet, t = triplet, m = multiplet, dd = doublet of doublets, dt = doublet of triplets.…”

“…In addition, it is involved in mitochondrial pathways and in the induction of stress in the endoplasmic reticulum, modes of action which might allow fludarabine to circumvent cancer cell drug resistance [ 12 ]. Studies have shown that inherent or acquired resistance to treatment with platinum drugs may be overcome by combining them with fludarabine, a combination that inhibits the nucleotide excision repair (NER) machinery, with the effect of preserving DNA defects [ 13 , 14 , 15 ]. Previously, our group found that treatment of CLL cells with combinations of fludarabine and metal complexes, e.g., Illudin-M ferrocene, resulted in enhanced cytotoxicity [ 16 ].…”

A nobel-winning scientist: aziz sancar and the impact of his work on the molecular pathology of neoplastic diseases

“…There is evidence that reduced TCR capacity increases the susceptibility of tumor cells to apoptosis induced by cisplatin even in cell lines with p53 mutation and DNA mismatch defects, and that the TCR system may be a potential target in overcoming cisplatin resistance in cancer treatment ( 97 ). For example, in experimental studies in chronic lymphocytic leukemia (CLL), TCR inhibition, in addition to the treatment regimen, has been shown to induce cell death regardless of the previous treatment and to have synergistic effects with the treatment regimen, revealing that it is a mechanism that can be used in refractory disease to re-sensitize CLL cells ( 98 , 99 ).…”