Sayak Banerjee, Amity University Kolkata
Scientists have come over a class of drugs utilized in the treatment of breast and ovarian cancer which might be effective in other types of diseases with inadequate treatment alternatives. These are called PARP inhibitors which have the potential to kill cancer cells carrying a defect in the Polybromo 1(PBRM1) gene.
PBRM1 is a particular subunit of the PBAF chromatin remodeling complex and its inactivation occurs recurrently in multiple malignancies, as well as 40% of clear cell renal cell carcinomas (ccRCC), a common type of kidney cancer that is of particular importance. PARP inhibitors are the class of drugs that are developed with the anticipation of inhibition of both PARP1 and PARP2 proteins. PARP or Poly(ADP-ribose) polymerase is a family of proteins associated with structural and functional similarity. PARP1 and PARP2 are enzymes or proteins significant in the base excision repair (BER) pathway for DNA single-strand breaks (SSB).
This mutation is also observed in mesothelioma, kidney cancer along with lung cancer, and bile duct cancers. The researchers said that, despite the defective PBMR1 gene being common, at present, no treatments are targeting them. In their findings, they have mentioned that PBMR1 could pose as progress towards the diagnosis of these forms of cancers. These common defects were overlooked for all these years because of the lack of technology required to identify them and come up with a treatment, until recently.
It was seen that the cancer cells deficient in PBMR1 protein had higher DNA damage levels. This became worse when it was treated with PARP inhibitors which include the drugs rucaparib, talazoparib, and olaparib causing the cells to die. The scientists had used a series of orthogonal functional genomic screens that recognized PARP and ATR inhibitors for being synthetically lethal to PBRM1 deficiency. The simultaneous use of PARP along with ATR inhibitors gave rise to additive cytotoxic effects in PBRM1-defective cancer cells. These synthetic lethal relationships were accompanied by pre-existing replication stress in PBRM1-deficient cells linked with mitosis and DNA damage repair aberrations. Hence, these findings provided a preclinical basis for the implementation of PARP inhibitors in PBRM1-defective cancers
Additionally, the subjection of the PBRM1-defective cancer cells to this class of drugs resulted in the activation of anti-cancer immune response in the body. This gives probable chances for the cancer patient to live for a longer period. Based on this observation, the scientists are looking towards clinical trials involving the combination of PARP inhibitors and immunotherapy in patients with PBMR1 faulty gene in cancer cells of kidney, bladder, lungs, and bile duct.
Thus, it was concluded that mutated PBMR1 genes are sensitive to PARP inhibitors, a class of drugs that renders the cancer cells deprived of their DNA defense mechanism. Researchers in Paris have already started clinical trials in cancer patients rooted in this finding. They hope that this could lead to a conspicuously novel genetically targeted approach for cancer diagnosis. They have stated that this could turn out to be a great genetic advancement in the history of the treatment of cancer as it is full of potential.
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Source:
Roman M. Chabanon, Daphné Morel, Thomas Eychenne, Léo Colmet-Daage, Ilirjana Bajrami, Nicolas Dorvault, Marlène Garrido, Cornelia Meisenberg, Andrew Lamb, Carine Ngo, Suzanna R. Hopkins, Theodoros I. Roumeliotis, Samuel Jouny, Clémence Hénon, Asuka Kawai-Kawachi, Clémence Astier, Asha Konde, Elaine Del Nery, Christophe Massard, Stephen J. Pettitt, Raphaël Margueron, Jyoti S. Choudhary, Geneviève Almouzni, Jean-Charles Soria, Eric Deutsch, Jessica A. Downs, Christopher J. Lord and Sophie Postel-Vinay Cancer Res June 1 2021 (81) (11) 2888-2902;DOI: http://10.1158/0008-5472.CAN-21-0628
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