Loss of heterozygosity of CYP2D6 enhances the sensitivity of hepatocellular carcinomas to talazoparib.

BACKGROUND: Loss of heterozygosity (LOH) diminishes genetic diversity within cancer genomes. A tumour arising in an individual heterozygous for a functional and a loss-of-function (LoF) allele of a gene occasionally retain only the LoF allele. This can result in deficiency of specific protein activities in cancer cells, creating unique differences between tumour cells and normal cells of the individual. Such differences may constitute vulnerabilities that can be exploited through allele-specific therapies. METHODS: To discover frequently lost genes with prevalent LoF alleles, we mined the 1000 Genomes dataset for SNVs causing protein truncation through base substitution, indels or splice site disruptions, resulting in 60 LoF variants in 60 genes. From these, the variant rs3892097 in the liver enzyme CYP2D6 was selected because it is located within a genomic region that frequently undergoes LOH in several tumor types including hepatocellular cancers. To evaluate the relationship between CYP2D6 activity and the toxicities of anticancer agents, we screened 525 compounds currently in clinical use or undergoing clinical trials using cell model systems with or without CYP2D6 activity. FINDINGS: We identified 12 compounds, AZD-3463, CYC-116, etoposide, everolimus, GDC-0349, lenvatinib, MK-8776, PHA-680632, talazoparib, tyrphostin 9, VX-702, and WZ-3146, using an engineered HEK293T cell model. Of these, talazoparib and MK-8776 demonstrated consistently heightened cytotoxic effects against cells with compromised CYP2D6 activity in engineered hepatocellular cancer cell models. Moreover, talazoparib displayed CYP2D6 genotype dependent effects on primary hepatocellular carcinoma organoids. INTERPRETATION: Exploiting the loss of drug-metabolizing enzyme gene activity in tumor cells following loss of heterozygosity could present a promising therapeutic strategy for targeted cancer treatment. FUNDING: This work was funded by Barncancerfonden (T.S, PR2022-0099 and PR2020-0171, X.Z, TJ2021-0111), Cancerfonden (T.S, 211719Pj and D.G, 222449Pj), Vetenskapsrådet (T.S, 2020-02371 and D.G, 2020-04707), and the Erling Persson Foundation (T.S, 2020-0037 and T.S, 2023-0113).

Next generation pan-cancer blood proteome profiling using proximity extension assay.

A comprehensive characterization of blood proteome profiles in cancer patients can contribute to a better understanding of the disease etiology, resulting in earlier diagnosis, risk stratification and better monitoring of the different cancer subtypes. Here, we describe the use of next generation protein profiling to explore the proteome signature in blood across patients representing many of the major cancer types. Plasma profiles of 1463 proteins from more than 1400 cancer patients are measured in minute amounts of blood collected at the time of diagnosis and before treatment. An open access Disease Blood Atlas resource allows the exploration of the individual protein profiles in blood collected from the individual cancer patients. We also present studies in which classification models based on machine learning have been used for the identification of a set of proteins associated with each of the analyzed cancers. The implication for cancer precision medicine of next generation plasma profiling is discussed.

Enhanced cytotoxicity of a novel family of ATPase inhibitors in colorectal cancer cells with high NAT2 activity.

Loss of heterozygosity (LOH) is a hallmark feature of cancer genomes that reduces allelic variation, thereby creating tumor specific vulnerabilities which could be exploited for therapeutic purposes. We previously reported that loss of drug metabolic arylamine N-acetyltransferase 2 (NAT2) activity following LOH at 8p22 could be targeted for collateral lethality anticancer therapy in colorectal cancer (CRC). Here, we report a novel compound CBK034026C that exhibits specific toxicity towards CRC cells with high NAT2 activity. Connectivity Map analysis revealed that CBK034026C elicited a response pattern related to ATPase inhibitors. Similar to ouabain, a potent inhibitor of the Na+/K+-ATPase, CBK034026C activated the Nf-kB pathway. Further metabolomic profiling revealed downregulation of pathways associated with antioxidant defense and mitochondrial metabolism in CRC cells with high NAT2 activity, thereby weakening the protective response to oxidative stress induced by CBK034026C. The identification of a small molecule targeting metabolic vulnerabilities caused by NAT2 activity provides novel avenues for development of anticancer agents.

Defining eligible patients for allele-selective chemotherapies targeting NAT2 in colorectal cancer.

Therapies targeting somatic bystander genetic events represent a new avenue for cancer treatment. We recently identified a subset of colorectal cancer (CRC) patients who are heterozygous for a wild-type and a low activity allele (NAT2*6) but lack the wild-type allele in their tumors due to loss of heterozygosity (LOH) at 8p22. These tumors were sensitive to treatment with a cytotoxic substrate of NAT2 (6-(4-aminophenyl)-N-(3,4,5-trimethoxyphenyl)pyrazin-2-amine, APA), and pointed to NAT2 loss being a therapeutically exploitable vulnerability of CRC tumors. To better estimate the total number of treatable CRC patients, we here determined whether tumor cells retaining also other NAT2 low activity variants after LOH respond to APA treatment. The prevalent low activity alleles NAT2*5 and NAT2*14, but not NAT2*7, were found to be low metabolizers with high sensitivity to APA. By analysis of two different CRC patient cohorts, we detected heterozygosity for NAT2 alleles targetable by APA, along with allelic imbalances pointing to LOH, in ~ 24% of tumors. Finally, to haplotype the NAT2 locus in tumor and patient-matched normal samples in a clinical setting, we develop and demonstrate a long-read sequencing based assay. In total, > 79.000 CRC patients per year fulfil genetic criteria for high sensitivity to a NAT2 LOH therapy and their eligibility can be assessed by clinical sequencing.