An in vitro and in vivo study of combination therapy with Photogem®-mediated photodynamic therapy and cisplatin on mouse cancer cells (CT-26).

Objective: This study was designed to evaluate the anticancer effect of cisplatin and photodynamic therapy (PDT) combined in vitro and in vivo.

Background Data: PDT, these days, is a promising modality for the treatment of cancer and infections. In order to optimize the treatment, cisplatin is often combined with other chemotherapeutic agents.

Methods: Colon cancer cells were incubated with cisplatin (0.1, 1, and 6 μg/ml), followed by photosensitization with Photogem® and irradiation with a 632 nm diode laser at an energy density of 3.2 J/cm(2). An MTT assay was then used to measure cell viability. For in vivo studies, established tumors were treated with cisplatin (3 mg/kg) alone or with PDT (5 mg/kg of Photogem®, 600 J/cm(2)). The sizes of the tumors were continuously measured to note the effects.

Results: The cell viability of the combined therapy group was 19.88 ± 0.41, corresponding to a 9% increase compared with that of the cisplatin- or PDT-only groups. In vivo, the tumors treated with PDT or combination therapy disappeared completely three days after each treatment, but on the 14th day, the recurrence rate was significantly lower in the combination therapy group than in the PDT group.

Conclusions: Combination therapy results in an enhanced anticancer effect, presenting the possibility of minimizing the administration dosage of Photogem® and cisplatin.