Identification of MEK2 and CBX7 as Top Steroid Resistant Genes in Airway ILC2s and Lymphocytes from Asthma

We reported that BAL ILC2s and lymphocytes (abbreviated as lymphoid cells) from asthmatic patients were steroid resistant in a TSLP-dependent manner. The mechanism of this steroid resistance is poorly understood. The induction of steroid resistant genes was studied by real-time PCR and flow cytometry. Interaction of MEK2 and CBX7 was studied by immunofluorescence staining and co-immunoprecipitation. Lymphoid cells were isolated from blood and BAL obtained from asthmatic patients, and from human lungs obtained from transplant-rejected donors. Using a genome-wide gene knockdown approach an earlier study identified about 50 steroid resistant genes in leukemic cells. We selected top 17 steroid resistant genes from this screen and examined their Dexamethasone (Dex) sensitivity in TSLP and IL33-stimulated lymphoid cells. Three of these 17 genes—CBX7 (a polycomb group repressor/co-activator), MEK2 and TLR2 were resistant to Dex. Unexpectedly, their induction by TSLP but not by IL33 was further augmented by Dex. TSLP induced MEK2, which translocated to the nucleus and physically interacted with CBX7. MEK2 and CBX7 cross-regulated each other’s expression indicating a positive feedback regulation. BAL lymphoid cells from refractory asthmatic patients showed increased expression of MEK2 and CBX7 as compared to disease controls. BAL lymphoid cell type 2 cytokine (IL5 and IL13) production in refractory asthma was resistant to Dex, which was reversed by Trametinib and MS37452, inhibitors of MEK2 and CBX7, respectively. We identified MEK2 and CBX7 as top steroid resistant genes in lymphoid cells from refractory asthma. MEK2 and CBX7 inhibitors are likely to benefit steroid-resistant asthma.