Effects of Zinc Protoporphyrin (Znpp) with Radiotherapy on Melanoma Tumor Growth in C57BL6 Mice

Decrease in Heme Oxygenase-1 gene expression is associated with fewer amounts of reoccurrence and better final response to treatment in some cancers. The aim of this study was to analyze the effect of Zinc Protoporphyrin (Znpp), as Heme Oxygenase-1 (HO-1) inhibitor, and radiotherapy on melanoma cells in mice.

In this experimental study, 24 mice were randomly divided to 4 groups. On the first day of the study, melanoma cells were injected and the mice were treated for 16 days. First and second groups received 2000 mg/kg of Znpp every other day. Third and forth groups were injected diluted liquid of Znpp. The first and third groups received 12 gray of radiotherapy on 8th day. The mice were examined each day for any palpable tumors and size was measured. The tumors were extracted on the 16th day. The effect of HO-1 on growth of cancer cells was studied using mitotic index and the size of tumors were measured on 8th and 16th days.

Size of tumor and mitotic index in mice treated with Znpp and radiotherapy was significantly smaller than in control groups (P < 0.05). Size of tumor in mice treated by radiotherapy and Znpp was less than group only treated with radiotherapy (P < 0.05).

The HO-1 inhibitor with radiotherapy may have therapeutic effects and it may be more effective in reducing the tumor’s growth than using radiotherapy alone.