Role of cAMP and protein kinase C signaling pathways in up-regulation of MAP-2. SK-MEL-19 melanoma cells were treated with 5 mmol/L of HMBA, 2.5 nmol/L of CT, 10 ng/ml TPA, or a combination of HMBA and CT or HMBA and TPA for 6, 24, and 48 hours. Ten μg of total RNA/lane was electrophoresed and blotted for Northern analysis. Blots were probed sequentially with 32P-labeled MAP-2, TYRP1, and GAPDH probes.