MAPK13 and neoplasm: Consistently, histologic analysis of tumor tissue, revealed vast areas of tumor necrosis in p38delta MAPK-depleted tumors (sth/p38δ 50%; sth/p38δ + 5FU 57.5%) in spite of a smaller tumor volume, as compared to control sth/scr tumors (sth/scr 28.7%; sth/scr + 5FU 32.5%) (Fig. 6d and Supplementary Table 3).