Targeting pan-essential pathways in cancer with cytotoxic chemotherapy: challenges and opportunities

Nelarabine in T-cell acute lymphoblastic leukemia: intracellular metabolism and molecular mode-of-action

T-cell acute lymphoblastic leukemia (T-ALL) patients often have a poor 5-year event-free survival. The only T-ALL specific drug in clinical practice is nelarabine. A prodrug of the deoxyguanosine analog ara-G, nelarabine is a rationally designed agent selective for the treatment of T-cell malignancies. Originally approved for relapsed/refractory T-ALL, it is increasingly used in T-ALL therapy and is currently being evaluated in upfront treatment. Whilst the clinical use of nelarabine has been the topic of multiple review articles, a thorough overview of the preclinical data detailing the molecular underpinnings of its anti-leukemic activity is lacking, which is critical to inform mechanism-based use. Thus, in the present article we conducted a semi-systematic review of the literature and critically evaluated the preclinical knowledge on the molecular pharmacology of nelarabine. Whilst early studies identified ara-G triphosphate to be the principal active metabolite and nuclear DNA synthesis to be a key target, many fundamental questions remain that could inform upon future use of this therapy. These include the nature of nelarabine-induced DNA lesions and their repair, together with additional cellular targets of ara-G metabolites and their role in efficacy and toxicity. A critical avenue of research in need of development is investigation of nelarabine combination therapies, both in the context of current T-ALL chemotherapy regimens and with emerging anti-leukemic agents, and we highlight some areas to pursue. Altogether, we discuss what we can learn from the preclinical literature as a whole and present our view for future research regarding nelarabine treatment in T-ALL.

Refining the role of N6-methyladenosine in cancer

N6-methyladenosine (m6A) is the most abundant internal modification of eukaryotic mRNAs. m6A affects the fate of its targets in all aspects of the mRNA life cycle and has important roles in various physiological and pathophysiological processes. Aberrant m6A patterns have been observed in numerous cancers and appear closely linked to oncogenic phenotypes. However, most studies relied on antibody-dependent modification detection, which is known to suffer from important limitations. Novel, antibody-independent, quantitative approaches will be critical to investigate changes in the m6A landscape of cancers. Furthermore, pharmaceutical targeting of the m6A writer Methyltransferase-like 3 (METTL3) has demonstrated the potential to modulate cancer cell phenotypes. However, the enzyme also appears to be essential for the viability of healthy cells. Further refinement of therapeutic strategies is therefore needed to fully realize the potential of m6A-related cancer therapies.

Understanding the interplay between dNTP metabolism and genome stability in cancer

The size and composition of the intracellular DNA precursor pool is integral to the maintenance of genome stability, and this relationship is fundamental to our understanding of cancer. Key aspects of carcinogenesis, including elevated mutation rates and induction of certain types of DNA damage in cancer cells, can be linked to disturbances in deoxynucleoside triphosphate (dNTP) pools. Furthermore, our approaches to treat cancer heavily exploit the metabolic interplay between the DNA and the dNTP pool, with a long-standing example being the use of antimetabolite-based cancer therapies, and this strategy continues to show promise with the development of new targeted therapies. In this Review, we compile the current knowledge on both the causes and consequences of dNTP pool perturbations in cancer cells, together with their impact on genome stability. We outline several outstanding questions remaining in the field, such as the role of dNTP catabolism in genome stability and the consequences of dNTP pool expansion. Importantly, we detail how our mechanistic understanding of these processes can be utilised with the aim of providing better informed treatment options to patients with cancer.

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) methods for the therapeutic drug monitoring of cytotoxic anticancer drugs: An update

In the era of precision medicine, there is increasing evidence that conventional cytotoxic agents may be suitable candidates for therapeutic drug monitoring (TDM)- guided drug dosage adjustments and patient's tailored personalization of non-selective chemotherapies. To that end, many liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) assays have been developed for the quantification of conventional cytotoxic anticancer chemotherapies, that have been comprehensively and critically reviewed. The use of stable isotopically labelled internal standards (IS) of cytotoxic drugs was strikingly uncommon, accounting for only 48 % of the methods found, although their use could possible to suitably circumvent patients' samples matrix effects variability. Furthermore, this approach would increase the reliability of cytotoxic drug quantification in highly multi-mediated cancer patients with complex fluctuating pathophysiological and clinical conditions. LC-MS/MS assays can accommodate multiplexed analyses of cytotoxic drugs with optimal selectivity and specificity as well as short analytical times and, when using stable-isotopically labelled IS for quantification, provide concentrations measurements with a high degree of certainty. However, there are still organisational, pharmacological, and medical constraints to tackle before TDM of cytotoxic drugs can be more largely adopted in the clinics for contributing to our ever-lasting quest to improve cancer treatment outcomes.