MAPK6 and lung carcinoma: Indeed, similar to knockdown of TDP2 (siTDP2), knockdown of ERK3 (siERK3) greatly increased H2AX phosphorylation (γ-H2AX, a marker of DNA damage) induced by either Etoposide (Figure 2A) or Teneposide (Figure 2B) in H460 lung cancer cells.