Loss of the Volume-regulated Anion Channel Components LRRC8A and LRRC8D Limits Platinum Drug Efficacy

Abstract

In recent years platinum (Pt) drugs have been found to be especially efficient to treat patients with cancers that lack a proper DNA damage response, e.g. due to dysfunctional BRCA1. Despite this knowledge, we are still missing helpful markers to predict Pt response in the clinic. We have previous-ly shown that volume-regulated anion channels, containing the subunits LRRC8A and LRRC8D, pro-mote the uptake of cisplatin and carboplatin in BRCA1-proficient cell lines. Here, we show that the loss of LRRC8A or LRRC8D significantly reduces the uptake of cis- and carboplatin in BRCA1;p53-deficient mouse mammary tumor cells. This results in reduced DNA damage and in vivo drug resistance. In contrast to Lrrc8a, the deletion of the Lrrc8d gene does not affect the viability and fertility of mice. Interestingly, Lrrc8d-/- mice tolerate a two-fold cisplatin maximum-tolerable dose. This allowed us to establish a mouse model for intensified Pt-based chemotherapy, and we found that an increased cis-platin dose eradicates BRCA1;p53-deficient tumors, whereas eradication is not possible in WT mice. Moreover, we show that decreased expression of LRRC8A/D in head and neck squamous cell carci-noma patients, who are treated with a Pt-based chemoradiotherapy, leads to decreased overall sur-vival of the patients. In particular, high cumulative cisplatin dose treatments lost their efficacy in pa-tients with a low LRRC8A/D expression in their cancers. Our data therefore suggest that LRRC8A and LRRC8D should be included in a prospective trial to predict the success of intensified cis- or car-boplatin-based chemotherapy.

Different Patterns of Platinum Resistance in Ovarian Cancer Cells with Homologous Recombination Proficient and Deficient Background

“…mRNA levels of the MDR-1 gene, which codes for the efflux pump responsible for the excretion of different anticancer drugs and whose increased levels have been reported in patients with platinum-resistant ovarian tumors, were lower in the F3 ddpR cells than parental ID8 F3 cells ( Figure 4 A), while there was a 3.4-fold upregulation in the Brca1−/− ddpR subline compared to the parental cells ( Figure 4 B). Besides transport pumps, DDP may enter the cell through ionic channels [ 10 ], so we evaluated the mRNA level of the volume-regulated anion channel LRRC8D gene: downregulation was clear in both F3 and Brca1−/− ddpR sublines compared to the corresponding parental cells ( Figure 4 A,B). Taken together, these data suggest slightly reduced DDP intracellular levels in both resistant sublines.…”

“…We too observed a 2.4-times upregulation of CTR2 in the F3 ddpR cells that may explain the lower DDP intracellular levels and the lower cytotoxic effect. Downregulation of both CTR1 and LRRC8D expression has been associated with lower DDP intracellular levels and cytotoxicity [ 10 , 49 ]. We found a 3-fold CTR1 decrease in Brca1−/− ddpR cells and 2.3- and 6-fold LRCC8D decreases, respectively, in F3 and Brca1−/− ddpR cells, suggesting a lower influx of cisplatin.…”

“…Different mechanisms underlying DDP resistance have been reported, including dysregulation of pumps/transporters such as the copper transporters 1 and 2 (CTR1 and CTR2), the ATPase copper-transporting alpha and beta (ATP7A and ATP7B) and the volume-regulated anion channels (VRAC) [ 9 , 10 ]. Platinum-induced DNA adducts are mainly repaired by nucleotide excision repair (NER), homologous recombination (HR) and mismatch repair (MMR), and the dysregulation of these pathways has been associated with DDP resistance [ 11 ].…”

Trends in volume-regulated anion channel (VRAC) research: visualization and bibliometric analysis from 2014 to 2022

“…Interestingly, when either LRRC8A or LRRC8D is knocked out, cancer cells exhibit a higher tolerance towards these platinum-based medications ( Planells-Cases et al, 2015 ). LRRC8 genes have been implicated in drug resistance and prognosis in various cancer types ( Sørensen et al, 2016 ; Xu et al, 2020 ; Siemer et al, 2021 ; Widmer et al, 2022 ; Xu et al, 2022 ).…”