For positive control on cell death, most cancer cells are sensitive to 1 uM Staurosporine for 8 h or 40 uM of cisplatin for 48 h. You can see a nice caspase 3 cleaved band or cleaved PARP on Western blot. Cell death can also be minotored by ELISA---> Cell Death Detection ELISAPLUS by Roche. Good luck!
Treatment with inflammatory cytokine (TNF-alpha, IL-1beta, or IL-6) at the higher concentration than the physiological one is expected to the positive control for the necrotic cellular change.
I agree with Go J Yoshida and the best one seems to be TNF-alpha to induce necrosis in carcinoma cell line. Hoping your research will go forward, best wishes.
Try with H202 (pure) to concentrations of 50, 100 or 200 microM tacking account the final volume of culture medium just for 5 to 15 minutes, but you can play with this concentration-time...