Some studies have suggested that nitric oxide may make resistant cancer cells more sensitive to chemotherapy, and that because of its importance to immunity, nitric oxide may strengthen anti-cancer resistance
On the other hand, several other studies suggest a negative effect.
For example, it is known that patients with lung cancer have high levels of nitric oxide within the tumor; higher levels are associated with advanced stages of cancer and poor survival.
Nitric oxide is also elevated with other tumors, including glioblastomas, breast cancers, and melanomas, and appears to increase the cancers’ aggressiveness.
Most impressive was the discovery that nitric oxide stimulated cancer stem cells and made tumors more aggressive.
The reason this is so important is that cancer stem cells are the source of tumor growth, invasion, recurrence, and metastasis — that is, everything that makes cancer deadly.
These special cells are also resistant to almost all forms of chemotherapy and radiation.
Other factors leading to increased cancer growth, invasion, and metastasis are also stimulated by higher levels of nitric oxide.
As you can see from this discussion, the answer is not always easy to discern. In some instances nitric oxide is beneficial, and other instances it can be quite harmful.
In fact, there are millions of people who have conditions that would be harmed by excess nitric oxide and an equal number who may benefit.
The key to whether or not a person may benefit from nitric oxide seems to be whether her or she is deficient to begin with.