Table 2.

The results of using LDN in polytherapy with cytostatics and other drugs with potential antitumor mechanisms.

Co-Treatments	Cancer	Mechanism/Results	References
LDN (10–5 mol/L), Taxol (10–9 or 10–10 mol/L), Cisplatin (0.01 or 0.001 µg/mL)	In vitro studies conducted on human ovarian cancer cell line SKOV-3	The number of cells exposed short-term to LDN and taxol was 36–61% lower compared to cells exposed only to LDN, and 19–31% lower compared to cells exposed only to taxol. The number of cells exposed to the short-term effects of LDN and cisplatin was reduced by 21–42% compared to cells exposed only to cisplatin.	[44]
Methylnaltrexone (1 µM) 5-Fluorouracil (10 µM)	In vitro studies conducted on human colorectal cancer cell lines SW-480, human breast cancer MCF-7, and non-small cell lung cancer cells	Inhibition of growth and proliferation by 63.5% in SW-480 cells, 58.3% in MCF-7 cells, and 81.3% in non-small cell lung cancer cells compared to groups treated only with 5FU.	[100]
MNTX (100 nmol/L), 5-FU (5 μmol/L), Bevacizumab (25 ng/mL)	In vitro studies conducted on human pulmonary microvascular EC (HPMVEC)	Methylnaltrexone (MNTX), synergistically with 5-FU and bevacizumab, inhibited vascular endothelial growth factor (VEGF)-induced human pulmonary microvascular endothelial cell (EC) proliferation and migration. MNTX inhibited EC proliferation with an IC(50) of approximately 100 nmol/L. The addition of MNTX to EC shifted the IC(50) of 5-FU from approximately 5 micromol/L to approximately 7 nmol/L. The addition of 50 MNTX shifted the IC(50) of bevacizumab in inhibiting EC migration from approximately 25 to approximately 6 ng/mL. RPTPμ activation inhibits VEGF-induced Src activation (target of bevacizumab). MNTX-induced Src inactivation results in activation of p190 RhoGAP and inhibition of active RhoA, which prevents reorganization of the actin cytoskeleton (targeted by 5-FU) and the resulting EC proliferation (targeted by 5-FU) and migration.	[101]
Naltrexone (10 nM–10 µM) Cannabidiol (CBD) (1 µM)	A549 (human lung cancer) and HCT116 (human colorectal cancer) cells	LDN and CBD reduced the number of cells. There was a 35% reduction in cell numbers when using LDN before CBD compared to a 22% reduction when using CBD before LDN.	[104]
LDN (0.1 mg/kg daily), Taxol (3 mg/kg, days 0, 7, 14, 21, 28, 35), Cisplatin (4 mg/kg days 0 and 7) intraperitoneal injections	Human ovarian cancer xenografts in female nude mice	Administration of NTX for six hours every two days, but not continuously, reduced DNA synthesis and cell replication compared to the control group. The combination of LDN with cisplatin, but not taxol, resulted in an additive inhibitory effect on tumorigenesis with enhanced depression of DNA synthesis and angiogenesis.	[44]
LDN (0.1 mg/kg), 5FU (20 mg/kg) subcutaneous injection	Human ovarian cancer xenografts in nude mice	A decrease in tumor mass and volume and an increase in the number of splenocytes, with a tendency to decrease the number of MDSC cells were observed. LDN led to an increase in OGFr both alone and in combination with 5FU, increased serum IFN-γ levels, but decreased when combined with 5-FU. The use of LDN and 5FU increased the expression of p21 and decreased Bcl2.	[99]
Low-Dose Methylnaltrexone (0.3 mg/kg) Docetaxel (Doc) (0.5 mg/kg)	60As6 human gastric cancer xenograft in female C.B17/Icr-scid mice	The growth of cells obtained from mice treated with a low-dose MNTX and Doc was significantly lower compared to mice treated with Doc only (Doc: 65.3 ± 6.6%, Doc/MNTX: 40.5 ± 7.1%). The use of Doc and low-dose MNTX polytherapy significantly extended life and alleviated cancer-related pain compared to mice treated with Doc only.	[102]
LDN (1.2 µg/mouse), CBD (35 µg/mouse), Gemcitabine (9 µg/mouse)	HCT116 colon cancer xenograft in athymic nu/nu BALB/c mice	The use of both compounds enhanced the effects of gemcitabine, without toxic effects.	[104]
NTX (0.001 µM to 200 µM) Propranolol (PRO) (0.001 µM to 200 µM)	Human breast cancer cells MDA-MB-231, MDA-MB-468, and T47D MDA-MB-231 xenograft in nude rat	Antitumor effects were observed due to the arrest of cell growth. NTX promoted PRO effects on expanded NK cells from the spleens and PBMCs of tumor xenografted animals. PRO and NTX increased the levels of NK cell-modulating cytokines while decreasing the levels of Th1 inflammatory cytokines.	[105]
LDN (0.1 mg/kg dose every 24 h for 24 weeks) orally, Carboplatin (300 mg/m2) intravenously	60 female dogs with mammary neoplasia	The higher serum concentrations of beta-endorphin and met-enkephalin, fewer chemotherapy-related side effects, and better quality of life and survival rates in the LDN-treated groups than in LDN-untreated groups. Evaluation of clinical and pathological parameters indicated a significant association between the use of LDN and prolonged survival, as well as enhanced quality of life.	[53]
NTX (100 mg) orally IL-2 (6 million lU/day subcutaneously for 6 days/week for 4 weeks)	14 consecutive untreatable metastatic solid tumor patients	The concomitant administration of NTX induced a significantly higher increase in lymphocyte mean number than that achieved with IL-2 plus MLT alone.	[44]
LDN (4.5 mg) α-Lipoic Acid (ALA) (300–600 mg)	64-year-old male patient diagnosed with metastatic renal cell carcinoma (RCC)	ALA could inhibit cancer cell growth by inhibiting the pro-inflammatory transcription factor, nuclear factor κ light chain enhancer of activated B cells (NF-κB). ALA, by inhibiting pyruvate dehydrogenase kinase (PDK), increases the activity of pyruvate dehydrogenase (PDHC), i.e., enzymes in the Warburg effect, inhibiting tumor development. Short-term opioid receptor blockade caused by LDN increases the production of enkephalin peptide, which, upon binding to OGFr, inhibits the proliferation of cancer cells.	[108]
LDN (3 mg) Vitamin D (10,000 IU daily)	58-year-old patient suffering from tonsillar-cystic tongue cancer without metastases	The patient has achieved nearly a four-year remission of his cancer based on his clinical status and the last MRI scan. LDN increases levels of the endogenous opioid methionine-enkephalin, which regulates cell proliferation and may inhibit the growth of cancer cells.	[107]