A Transient Metabolic State In Melanoma Persister Cells Mediated By Chemotherapeutic Treatments

Abstract

Persister cells are defined as the small fraction of quiescent cells in a bulk cancer cell population that can tolerate unusually high levels of drugs. Persistence is a transient state that poses an important health concern in cancer therapy. The mechanisms associated with persister phenotypes are highly diverse and complex, and many aspects of persister cell physiology remain to be explored. We applied a melanoma cell line and panel of chemotherapeutic agents to show that melanoma persister cells are not necessarily preexisting dormant cells or stem cells; in fact, they may be induced by cancer chemotherapeutics. Our metabolomics analysis and phenotype microarray assays further demonstrated that the levels of Krebs cycle molecules are significantly lower in the melanoma persister subpopulation than in the untreated bulk cell population due to increased utilization rates in persisters. Our data indicate that this observed metabolic remodeling is transient, as the consumption rates of Krebs cycle metabolites are significantly reduced in the progenies of persisters. Given that the mitochondrial electron transport chain (ETC) is more active in the persister subpopulation than in the bulk cancer cell population, we also verified that targeting ETC activity can reduce melanoma persistence. The reported metabolic remodeling feature seems to be a conserved characteristic of melanoma persistence, as it has been observed in various melanoma persister subpopulations derived from a diverse range of chemotherapeutics. Elucidating a global metabolic mechanism that contributes to persister survival and reversible switching will ultimately foster the development of novel cancer therapeutic strategies.

BRAF-Inhibitor-Induced Metabolic Alterations in A375 Melanoma Cells

“…We first treated A375 cells with different concentrations of VEM for 3 days to generate a kill curve (survival ratio vs. VEM concentration) (Figure 1a). The data show that the half maximal inhibitory concentration (IC 50 ) of VEM for A375 cells was ~100 nM and a treatment concentration higher than 10 × IC 50 did not significantly affect the persister ratio (i.e., cell survival ratio) [17]. As persisters survive high concentrations of drugs, persister cells were isolated by treating A375 cells with VEM at 100 × IC 50 concentration for 3 days, consistent with previous studies [17,19,20].…”

“…The data show that the half maximal inhibitory concentration (IC 50 ) of VEM for A375 cells was ~100 nM and a treatment concentration higher than 10 × IC 50 did not significantly affect the persister ratio (i.e., cell survival ratio) [17]. As persisters survive high concentrations of drugs, persister cells were isolated by treating A375 cells with VEM at 100 × IC 50 concentration for 3 days, consistent with previous studies [17,19,20]. After treatment, the cells were cultured in a fresh, drug-free growth medium for 24 h to remove dead/apoptotic cells.…”

“…In addition, studies have demonstrated that BRAF-inhibitor-tolerant cells shift their metabolic activity away from aerobic glycolysis and toward oxidative phosphorylation, which is mediated via fatty acid oxidation [16]. In our previous study, we explored the impacts of conventional chemotherapeutics (cytotoxic medications) on persister metabolism and found that chemotherapeutics induce a transient shift from aerobic glycolysis to oxidative phosphorylation [17]. When it comes to targeted therapeutics, melanoma persister cells are generally derived by co-treatment with BRAF/MEK inhibitors [16], making it unclear how persister metabolism is affected by each drug, individually.…”

Systems-level network modeling deciphers the master regulators of phenotypic plasticity and heterogeneity in melanoma

“…While shorter duration of BRAF and RAF/MEK inhibition gives rise to NCSC phenotype (NGFR+ cells), prolonged exposure facilitates undifferentiated cells ( Fallahi-Sichani et al., 2017 ; Su et al., 2017 ). How does adaptation at different time scales contribute to emergence and maintenance of drug-tolerant persisters ( Shaffer et al., 2017 ; Ahmed and Haass, 2018 ; Schuh et al., 2020 ), and the role of reversible cellular reprogramming ( Roesch et al., 2010 ; Karki et al., 2021 ) in enabling such persisters requires further careful investigation. Understanding the dynamics and trajectories of phenotypic switching in these scenarios can help guide better combinatorial ( Boshuizen et al., 2018 ; Luo et al., 2018 ) and/or sequential ( Goldman et al., 2015 ) therapies that can target vulnerabilities of diverse phenotypes.…”

Cancer: More Than a Geneticist’s Pandora’s Box

“…DTPs adapt to environmental fluctuations through epigenomic, transcriptional and metabolic reprogramming events, and are capable of expanding into a colony (Shen et al, 2020b). Initially reported in lung cancer (Sharma et al, 2010), persisters have been reported in other cancer types as well such as melanoma and colorectal cancer (Hangauer et al, 2017;Karki et al, 2021;Mikubo et al, 2021;Oren et al, 2021;Rehman et al, 2021;Shen et al, 2020a). Intriguingly, DTPs can act as a reservoir subpopulation through which genetically mutated cells can emerge to stabilize diverse drug-resistance mechanisms at a longer time-scale (Ramirez et al, 2016).…”