Combined effects of laser-ICG photothermotherapy and doxorubicin chemotherapy on ovarian cancer cells

Doxorubicin (DOX) is an anthracycline antibiotic widely used in cancer chemotherapy. Its use is limited by cardiac toxicity and drug resistance. Hyperthermia can aid the functionality of DOX, but current hyperthermia delivery methods are hard to apply selectively and locally. The slow temperature increase associated with the external heating may lead to thermal tolerance in cancer cells. The FDA approved dye indocynine green (ICG) has been demonstrated to absorb near-infrared (NIR) light at 808 nm (ideal for tissue penetration) and emit the energy as heat, making it an ideal agent for localized hyperthermia with a rapid rate of temperature increase. The purpose of this study was to investigate the in vitro cytotoxic effect of combined chemotherapy and hyperthermia to a DOX resistant ovarian cancer cell line (SKOV-3). The effect of two different heating methods, ICG induced rapid rate heating and an incubator induced slow rate heating, were compared. All the experiments were conducted in 96-well plates. Cells were subjected to different concentrations of DOX and 60 min 43 °C incubation or 5 μM of ICG with 1 min 808 nm NIR laser. SRB assay was used to measure cell proliferation. ICG itself without laser irradiation was not toxic to SKOV-3 cells. The two types of hyperthermia individually produced similar cytotoxicity. DOX by itself was toxic with an IC 50 value of about 5 μM. Hyperthermia in combination with DOX achieved significantly greater cell killing/growth inhibition at all DOX concentrations compared to DOX alone. A subadditive cytotoxic effect was observed by combining DOX and 60 min 43 °C incubation which lead to a lowered DOX IC 50 value of about 1 μM. This value was even lower with 1 min laser-ICG photothermotherapy (0.1 μM) and, though not statistically significant, a synergistic effect may exist between DOX and laser-ICG photothermotherapy. The rate of heating may have an effect on chemotherapy–hyperthermia interaction. In conclusion, the combination of photothermal therapy and chemotherapy may provide a valuable tool for cancer treatment with minimized side effect.