Sensitizing thermochemotherapy with a PARP1-inhibitor

Area of Science:

• Oncology
• Molecular Biology
• Cancer Therapeutics

Background:

• Cis-diamminedichloroplatinum(II) (cisplatin, cDDP) induces DNA double-strand breaks (DSBs), crucial for its chemotherapeutic effect.
• DSB repair mechanisms include classical non-homologous end joining (c-NHEJ), backup non-homologous end joining (b-NHEJ), and homologous recombination (HR).
• Hyperthermia (HT) inhibits HR, enhancing cDDP efficacy, and is used in treating recurrent cervical cancer.

Purpose of the Study:

• To investigate if inhibiting Poly-(ADP-ribose)-polymerase1 (PARP1)-dependent b-NHEJ enhances the efficacy of cisplatin and hyperthermia combination therapy.
• To explore the potential of PARP1 inhibition to reduce cisplatin concentrations while maintaining therapeutic effectiveness.

Main Methods:

• Treatment of various cancer cell lines with hyperthermia (HT), cisplatin (cDDP), and a PARP1 inhibitor (PARP1-i).
• Measurement of endpoints relevant to cancer treatment efficacy and toxicity.
• Evaluation of combination therapy effects at standard and reduced cDDP concentrations.

Main Results:

• PARP1 inhibition did not significantly increase the efficacy of HT and standard cDDP concentrations.
• In the presence of a PARP1 inhibitor, a tenfold lower concentration of cDDP achieved similar cytotoxic effects.
• This suggests PARP1 inhibition may allow for dose reduction of cDDP without compromising efficacy.

Conclusions:

• PARP1 inhibition offers a strategy to lower cisplatin doses in combination therapy, potentially mitigating systemic side effects.
• The findings support exploring reduced cDDP concentrations in thermochemotherapy regimens when combined with PARP1 inhibitors.