Translational issues with phototherapy of cancer

Cancer is one of the most common and deadly diseases which has challenged human knowledge since its discovery. There are a variety of therapies, such as radiotherapy, chemotherapy, palliative surgery, medicine, and gene therapy, used for patients suffering from cancer, all of which represent, to some extent, a kind of failure. However, a number of novel strategies based on nanotechnology (including, photodynamic therapy [PDT] and photothermal therapy [PTT]) have been introduced in recent years, which appear to have the ability to be used as an auxiliary treatment for chemotherapy and radiotherapy in the future. Interestingly, cancer cells, in response to various therapeutic factors, can utilize certain cellular mechanisms and processes for their survival and growth. For example, macro autophagy/autophagy, can alter the cancer cell fate, from autophagic cell death to dormancy (as a key factor in tumor recurrence). Nonetheless, there have been conflicting conclusions regarding the interactions of phototherapy methods with cells as well as their wanted or unwanted impacts on these cells. In addition, there are complicated and controversial associations among the most common cell death mechanisms such as apoptosis, autophagy, and necrosis as well as tumor treatment and recurrence. The present review aims to describe various responses of cancer cells to photo-based therapy, which can control cell death or dormancy. Moreover, we discuss whether the incorrect application of various phototherapy parameters not only fails to treat and eradicate cancerous tumors, but also mediates the entry of tumor cells into the dormancy phase or even promotes a cancer flare up.