CGRP increases the resistance of receptor positive human AML cell lines to drugs used in the treatment of AML. (a) Expression of CALCRL and RAMP1 in the human myeloid cell lines HNT-34, UKK-M7, U937, and HL-60 was determined by qRT-PCR. Normalization to β-2-microglobulin mRNA levels and calibration to HNT-34 was performed using the ΔΔCT method. n.d., not detectable. Means + SEM from 3 biological replicates. (b) Proliferation of HNT-34 and UKK-M7 cells in the absence or presence of 100 nM CGRP. Means +/− SEM from 3 biological replicates. (c,d) CGRP protects HNT-34 and UKK-M7 cells from araC- and daunorubicin (DNR)-induced apoptosis. Cells were pre-incubated with or without 100 nM CGRP for 1 h prior to addition of the indicated concentrations of cytostatic drugs. Means +/− SEM from 3–5 biological replicates. ns, not significant, * p < 0.05, ** p < 0.01, *** p < 0.001, paired Student’s two-tailed t-test. (c) CellTiter-Glo metabolic activity assay. (d) AnnexinV/DAPI assay.