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While the effect of amplification-induced oncogene expression in cancer is known, the impact of copy-number gains on "bystander" genes is less understood. We create a comprehensive map of dosage compensation in cancer by integrating expression and copy number profiles from over 8000 tumors in The Cancer Genome Atlas and cell lines from the Cancer Cell Line Encyclopedia. Additionally, we analyze 17 cancer open reading frame screens to identify genes toxic to cancer cells when overexpressed. Combining these approaches, we propose a class of 'Amplification-Related Gain Of Sensitivity' (ARGOS) genes located in commonly amplified regions, yet expressed at lower levels than expected by their copy number, and toxic when overexpressed. We validate RBM14 as an ARGOS gene in lung and breast cancer cells, and suggest a toxicity mechanism involving altered DNA damage response and STING signaling. We additionally observe increased patient survival in a radiation-treated cancer cohort with RBM14 amplification.

Inhibitors of murine double minute homolog 2 (MDM2) represent a promising therapeutic approach for the treatment of TP53 wild-type glioblastomas (GBMs), reactivating p53 signaling to induce cancer cell death. We conducted a surgical window-of-opportunity trial (NCT03107780) of the MDM2 inhibitor navtemadlin (KRT-232) in 21 patients with TP53 wild-type recurrent GBM to determine achievable drug concentrations within tumor tissues and biological mechanisms of response and resistance. Participants received navtemadlin at 120 mg (n = 10) or 240 mg (n = 11) for 2 days before surgical resection and after surgery until progression or unacceptable toxicity. Both 120 and 240 mg daily dosing achieved a pharmacodynamic impact, but median progression-free survival was 3.1 months. DNA sequencing of three recurrent tumors revealed an absence of TP53-inactivating mutations, indicating alternative mechanisms of resistance. To understand the mechanisms of response and resistance associated with navtemadlin, we conducted functional and spatial analyses of human tissue and patient-derived GBM neurosphere models. Navtemadlin induced partial tumor cell death as monotherapy, and combination with temozolomide enhanced apoptosis in GBM neurospheres while sparing normal bone marrow cells in vitro. We also observed up-regulation of oligodendrocyte differentiation genes with navtemadlin treatment and enrichment of oligodendrocyte transcription factor 2 (OLIG2)–positive cells at relapse, suggesting an unexplored mechanism of navtemadlin tolerance in GBM. Overall, these results indicated that clinically achievable doses of navtemadlin exert pharmacodynamic effects on GBM and suggest that combined treatment with temozolomide may be a route to more durable survival benefits.

The Arylamine-N-acetyltransferase-2 (NAT2) enzyme is involved in metabolism of commonly used drugs driving differences in efficacy and tolerability of treatments. To bridge the current knowledge gap on metabolism of cytotoxic drugs by NAT2, and identify anticancer agents whose effects depend on NAT2 activity, we assessed 147 clinically used drugs. Hit compounds were evaluated for metabolic conversion by acetylation in presence of recombinant NAT2. Among those 147 drugs we found doxorubicin, daunorubicin, epirubicin, valrubicin, teniposide, afatinib, carmustine, vincristine, panobinostat, and vorinostat to have increased toxicity to cancer cells expressing the rapid NAT2 allele. Additionally, we report NAT2-mediated acetylation of idarubicin, daunorubicin, doxorubicin, vorinostat, and CUDC-101. These findings have implications for pharmacogenomics and cancer precision medicine using conventional chemotherapeutic drugs, as improving their efficacy and safety may affect >4 million cancer patients worldwide that receive these drugs as standard of care.

Glioblastoma (GBM) is a highly malignant brain tumor with extensive cellular heterogeneity and plasticity. Bone morphogenetic protein 4 (BMP4) has shown potential as a therapeutic agent by promoting differentiation, but its effects are complex and context dependent. While BMP4's role in differentiation is well established, its impact on senescence remains unclear. This study investigates BMP4's ability to induce senescence in GBM cells. Primary GBM cultures were treated with BMP4 and analyzed for senescence markers, including cell enlargement, p21 expression, senescence-related gene enrichment, and senescence-associated-beta-galactosidase activity. A p21 knockout model was used to determine its role in BMP4-induced senescence, and sensitivity to the senolytic agent navitoclax was evaluated. BMP4 induced senescence in the GBM cultures, particularly in mesenchymal (MES)-like GBM cells with high baseline p21 levels. The knockout of p21 nearly abolished BMP4-induced senescence, maintaining cell size and proliferation. Furthermore, navitoclax effectively eliminated BMP4-induced senescent cells through apoptosis, while sparing cells with normal p21 expression. Our findings highlight BMP4 as an inducer of p21-dependent senescence in GBM, particularly in MES-like cells. This study clarifies BMP4's dual roles in differentiation and senescence, emphasizing their context dependence. Given the strong link between MES-like cells and therapy resistance, their heightened susceptibility to senescence may aid in developing targeted therapies for GBM and potentially other cancers with similar cellular dynamics.

Recent work by the ICGC-PCAWG consortium identified recurrent focal deletions in the BRD4 gene, decreasing expression despite increased copy number. We show that these focal deletions occur in the context of cyclin E1 amplification in breast, ovarian, and endometrial cancers, and serve to disrupt BRD4 regulatory regions and gene expression across isoforms. We analyze open reading frame screen data and find that overexpression of BRD4 long (BRD4-L) and short isoform BRD4-S(a) impairs cell growth across cell lines. We confirm these results in OVSAHO ovarian cancer cells, where the overexpression of BRD4 isoforms significantly reduces tumor growth. Next, we mimic BRD4 focal deletions using CRISPR-Cas9 technology and show that these focal deletions rescue ovarian cancer cells from toxicity associated with BRD4 overexpression, suggesting that BRD4 levels must be fine-tuned for cancer cell proliferation. Our study provides experimental evidence for the first recurrent deletion reducing toxicity in cancer, expanding the landscape of cancer progression mechanisms.

Functional precision medicine (FPM) aims to optimize patient-specific drug selection based on the unique characteristics of their cancer cells. Recent advancements in high throughput ex vivo drug profiling have accelerated interest in FPM. Here, we present a proof-of-concept study for an integrated experimental system that incorporates ex vivo treatment response with a single-cell gene expression output enabling barcoding of several drug conditions in one single-cell sequencing experiment. We demonstrate this through a proof-of-concept investigation focusing on the glucocorticoid-resistant acute lymphoblastic leukemia (ALL) E/R+ Reh cell line. Three different single-cell transcriptome sequencing (scRNA-seq) approaches were evaluated, each exhibiting high cell recovery and accurate tagging of distinct drug conditions. Notably, our comprehensive analysis revealed variations in library complexity, sensitivity (gene detection), and differential gene expression detection across the methods. Despite these differences, we identified a substantial transcriptional response to fludarabine, a highly relevant drug for treating high-risk ALL, which was consistently recapitulated by all three methods. These findings highlight the potential of our integrated approach for studying drug responses at the single-cell level and emphasize the importance of method selection in scRNA-seq studies. Finally, our data encompassing 27 327 cells are freely available to extend to future scRNA-seq methodological comparisons.

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.

Background: Genes in the Ras pathway have somatic mutations in at least 60 % of colorectal cancers. Despite activating the same pathway, the BRAF V600E mutation and the prevalent mutations in codon 12 and 13 of KRAS have all been linked to different clinical outcomes, but the molecular mechanisms behind these differences largely remain to be clarified.

Methods: To characterize the similarities and differences between common activating KRAS mutations and between KRAS and BRAF mutations, we used genome editing to engineer KRAS G12C/D/V and G13D mutations in colorectal cancer cells that had their mutant BRAF V600E allele removed and subjected them to transcriptome sequencing, global proteomics and metabolomics analyses.

Results: By intersecting differentially expressed genes, proteins and metabolites, we uncovered (i) two-fold more regulated genes and proteins when comparing KRAS to BRAF mutant cells to those lacking Ras pathway mutation, (ii) five differentially expressed proteins in KRAS mutants compared to cells lacking Ras pathway mutation (IFI16, S100A10, CD44, GLRX and AHNAK2) and 6 (CRABP2, FLNA, NXN, LCP1, S100A10 and S100A2) compared to BRAF mutant cells, (iii) 19 proteins expressed differentially in a KRAS mutation specific manner versus BRAF V600E cells, (iv) regulation of the Integrin Linked Kinase pathway by KRAS but not BRAF mutation, (v) regulation of amino acid metabolism, particularly of the tyrosine, histidine, arginine and proline pathways, the urea cycle and purine metabolism by Ras pathway mutations, (vi) increased free carnitine in KRAS and BRAF mutant RKO cells.

Conclusions: This comprehensive integrative -omics analysis confirms known and adds novel genes, proteins and metabolic pathways regulated by mutant KRAS and BRAF signaling in colorectal cancer. The results from the new model systems presented here can inform future development of diagnostic and therapeutic approaches targeting tumors with KRAS and BRAF mutations.

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 similar to 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.

Allelic losses occurring in cancer cells have been suggested as potential targets for therapy. Here, the authors show how recurring loss of heterozygosity of a drug metabolic gene in colorectal cancers can be exploited using a low molecular weight compound. Cancer chemotherapy targeting frequent loss of heterozygosity events is an attractive concept, since tumor cells may lack enzymatic activities present in normal constitutional cells. To find exploitable targets, we map prevalent genetic polymorphisms to protein structures and identify 45 nsSNVs (non-synonymous small nucleotide variations) near the catalytic sites of 17 enzymes frequently lost in cancer. For proof of concept, we select the gastrointestinal drug metabolic enzyme NAT2 at 8p22, which is frequently lost in colorectal cancers and has a common variant with 10-fold reduced activity. Small molecule screening results in a cytotoxic kinase inhibitor that impairs growth of cells with slow NAT2 and decreases the growth of tumors with slow NAT2 by half as compared to those with wild-type NAT2. Most of the patient-derived CRC cells expressing slow NAT2 also show sensitivity to 6-(4-aminophenyl)-N-(3,4,5-trimethoxyphenyl)pyrazin-2-amine (APA) treatment. These findings indicate that the therapeutic index of anti-cancer drugs can be altered by bystander mutations affecting drug metabolic genes.