Glucocorticoid Receptor Status Is a Principal Determinant of Variability in the Sensitivity of Non–Small-Cell Lung Cancer Cells to Pemetrexed

Abstract

Introduction Pemetrexed is an S-phase targeted drug in front-line or maintenance therapy of advanced non-squamous non-small cell lung cancer (NSCLC) but methods are needed for predicting the drug response. Dexamethasone is typically administered the day before, the day of and the day after pemetrexed. As dexamethasone strongly regulates many genes including p53 through the glucocorticoid receptor (GR), we hypothesized that dexamethasone influences tumor response to pemetrexed. Methods Eight non-squamous NSCLC cell line models with varied p53 and GRα/GRβ status were used for gene expression and cell cycle analyses and for loss/gain-of-function experiments. Results In three cell lines dexamethasone profoundly, but reversibly, suppressed the fraction of S-phase cells. Dexamethasone also reversibly repressed expression of thymidylate synthase and dihydrofolate reductase which are primary targets of pemetrexed but are also quintessential S-phase enzymes as well as the S-phase dependent expression of thymidine kinase 1. Dexamethasone also decreased expression of the major pemetrexed transporters, the reduced folate carrier and the proton coupled folate transporter. Only cells expressing relatively high GRα showed these dexamethasone effects, regardless of p53 status. In cells expressing low GRα, the dexamethasone response was rescued by ectopic GRα. Further, depletion of p53 did not attenuate the dexamethasone effects. The presence of dexamethasone during pemetrexed treatment protected against pemetrexed cytotoxicity, in only the dexamethasone responsive cells. Conclusions The results predict that in non-squamous NSCLC tumors, reversible S-phase suppression by dexamethasone, possibly combined with a reduction in the drug transporters, attenuates responsiveness to pemetrexed and that GR status is a principal determinant of tumor variability of this response.

Glucocorticoid receptors in lung cancer: new perspectives

“…The importance of sufficient GR is highlighted as dexamethasone effects are not dependent on p53 but rather dependent on the GR status, as dexamethasone treatment did not influence pemetrexed effects on H1299 cells (which contain low levels of GRα) (Patki et al 2014). Lack of sensitivity to pemetrexed action was restored in H1299 cells transduced with exogenous GR and pretreated with dexamethasone for 48 h (Patki et al 2014). Dexamethasone pre-treatment for 24 h also decreased sensitivity towards cisplatin in GR-containing H460 NSCLC cells (Lu et al 2005).…”

“…In vitro studies using a variety of different NSCLC cell lines show that dexamethasone treatment affects sensitivity to pemetrexed or cisplatin chemotherapy (Herr et al 2003, Gassler et al 2005, Ge et al 2012, Patki et al 2014. The importance of sufficient GR is highlighted as dexamethasone effects are not dependent on p53 but rather dependent on the GR status, as dexamethasone treatment did not influence pemetrexed effects on H1299 cells (which contain low levels of GRα) (Patki et al 2014).…”

“…In p53-null H1299 cells (a lung adenocarcinoma cell line) that also express low levels of the GR, dexamethasone had no effect on cell proliferation; however, the inhibitory effects on proliferation were restored by restoring GR expression ectopically in these cells. High levels of GR in this context may, therefore, be sufficient to overcome the lack of p53 (Patki et al 2014).…”

Targeting Nonsquamous Nonsmall Cell Lung Cancer via the Proton-Coupled Folate Transporter with 6-Substituted Pyrrolo[2,3-d]Pyrimidine Thienoyl Antifolates

“…Thymidylate synthase (TS) is the primary intracellular enzyme target for PMX (Chattopadhyay et al, 2007) and TS levels have been implicated in some studies as an important determinant of PMX clinical response, such that tumors with highly elevated TS would be expected to show PMX resistance (Christoph et al, 2013;Liu et al, 2013). At least some of the variable responses to PMX seen clinically may reflect an impact of coadministering dexamethasone with PMX to alleviate possible side effects since dexamethasone attenuates PMX cytotoxicity in NS-NSCLC cells by reversibly blocking cell cycle progression, secondary to the presence of high levels of the glucocorticoid receptor a (Patki et al, 2014). Interestingly, dexamethasone treatment of NS-NSCLC cells in vitro also resulted in reduced expression of RFC and PCFT (Patki et al, 2014).…”

“…At least some of the variable responses to PMX seen clinically may reflect an impact of coadministering dexamethasone with PMX to alleviate possible side effects since dexamethasone attenuates PMX cytotoxicity in NS-NSCLC cells by reversibly blocking cell cycle progression, secondary to the presence of high levels of the glucocorticoid receptor a (Patki et al, 2014). Interestingly, dexamethasone treatment of NS-NSCLC cells in vitro also resulted in reduced expression of RFC and PCFT (Patki et al, 2014). PMX can inhibit folate-dependent enzymes other than TS, including glycinamide ribonucleotide formyltransferase (GARFTase) and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase in de novo purine nucleotide biosynthesis (Shih and Thornton, 1999;Racanelli et al, 2009).…”