Low-Dose Naltrexone as an Adjuvant in Combined Anticancer Therapy.

Simple Summary: This review aims to present current evidence on the potential use of low-dose naltrexone (LDN) in cancer therapy. Low-dose naltrexone exhibits an inhibitory effect on cancer cell proliferation by blocking the opioid growth factor–receptor axis and enhancing the immune response against cancer cells. Data from existing studies indicate that low-dose naltrexone has a high anti-cancer potential, especially as an adjuvant in conventional chemotherapy and immunotherapy schemes. Naltrexone (NTX) is a non-selective antagonist of opioid receptors, primarily used in the therapy of opioid and alcohol dependence. Low-dose naltrexone (LDN) exhibits antagonistic action against the opioid growth factor receptor (OGFr), whose signaling is associated with the survival, proliferation, and invasion of cancer cells. The mechanism of action of LDN depends on the dose and duration of the OGFr blockade, leading to a compensatory increase in the synthesis of the opioid growth factor (OGF), which has an inhibitory effect on carcinogenesis. Numerous studies on in vitro and in vivo models provide evidence of LDN's positive impact on inhibiting the OGF–OGFr axis in cancers. LDN's unique mechanism of action on cancer cells, lack of direct cytotoxic effect, and immunomodulating action form the basis for its use as an adjuvant in chemotherapy and immunotherapy of cancerous lesions. [ABSTRACT FROM AUTHOR]