Nitric oxide-mediated activity in anti-cancer photodynamic therapy

Area of Science:

• Oncology
• Photochemistry
• Molecular Biology

Background:

• Cancer recurrence after photodynamic therapy (PDT) is a significant clinical challenge.
• Nitric oxide (NO) is increasingly recognized as a key modulator of PDT efficacy.
• NO influences cancer cell apoptosis via the NF-κB/Snail/RKIP signaling pathway.

Purpose of the Study:

• To investigate the role of nitric oxide (NO) in modulating pheophorbide a/PDT (Pba/PDT) efficacy.
• To determine if combining Pba/PDT with an NO donor enhances anti-cancer effects in melanoma cells and tumors.

Main Methods:

• B78-H1 murine melanoma cells were treated with varying doses of Pba/PDT and a nitric oxide donor (DETA/NO).
• Cell viability and growth were assessed using scratch-wound and clonogenic assays.
• Western blot analysis was performed to evaluate protein expression changes in key survival and apoptotic pathways.
• In vivo studies utilized C57BL/6 mice bearing B78-H1 melanoma, treated with pegylated Pba (mPEG-Pba) and DETA/NO, followed by photoactivation.

Main Results:

• Pba/PDT induced NO release in a dose-dependent manner, with low doses promoting survival and high doses inducing apoptosis.
• Combined treatment with low-dose Pba/PDT and DETA/NO inhibited cell growth and reduced anti-apoptotic proteins (NF-κB, Snail) while increasing pro-apoptotic RKIP.
• In vivo, the combination of mPEG-Pba and DETA/NO significantly delayed tumor growth compared to individual treatments.

Conclusions:

• Nitric oxide plays a dual role in modulating PDT-induced apoptosis, dependent on its concentration.
• Combining Pba/PDT with an NO donor enhances anti-cancer efficacy by promoting apoptosis through the NF-κB/Snail/RKIP pathway.
• This combination therapy represents a promising strategy to improve PDT outcomes and overcome cancer recurrence.