Role of Silymarin in Cancer Treatment: Facts, Hypotheses, and Questions

Abstract

The flavonoid silymarin extracted from the seeds of Sylibum marianum is a mixture of 6 flavolignan isomers. The 3 more important isomers are silybin (or silibinin), silydianin, and silychristin. Silybin is functionally the most active of these compounds. This group of flavonoids has been extensively studied and they have been used as hepato-protective substances for the mushroom Amanita phalloides intoxication and mainly chronic liver diseases such as alcoholic cirrhosis and nonalcoholic fatty liver. Hepatitis C progression is not, or slightly, modified by silymarin. Recently, it has also been proposed for SARS COVID-19 infection therapy. The biochemical and molecular mechanisms of action of these substances in cancer are subjects of ongoing research. Paradoxically, many of its identified actions such as antioxidant, promoter of ribosomal synthesis, and mitochondrial membrane stabilization, may seem protumoral at first sight, however, silymarin compounds have clear anticancer effects. Some of them are: decreasing migration through multiple targeting, decreasing hypoxia inducible factor-1α expression, inducing apoptosis in some malignant cells, and inhibiting promitotic signaling among others. Interestingly, the antitumoral activity of silymarin compounds is limited to malignant cells while the nonmalignant cells seem not to be affected. Furthermore, there is a long history of silymarin use in human diseases without toxicity after prolonged administration. The ample distribution and easy accessibility to milk thistle—the source of silymarin compounds, its over the counter availability, the fact that it is a weed, some controversial issues regarding bioavailability, and being a nutraceutical rather than a drug, has somehow led medical professionals to view its anticancer effects with skepticism. This is a fundamental reason why it never achieved bedside status in cancer treatment. However, in spite of all the antitumoral effects, silymarin actually has dual effects and in some cases such as pancreatic cancer it can promote stemness. This review deals with recent investigations to elucidate the molecular actions of this flavonoid in cancer, and to consider the possibility of repurposing it. Particular attention is dedicated to silymarin's dual role in cancer and to some controversies of its real effectiveness.

Silymarin Based Complexes – a mini review

“…To increase bioavailability and solubility of silymarin were developed complexes with cyclodextrins and phospholipids, microemulsions, nanoemulsions, liposomes, polymer nanocarriers, solid-lipid nanoparticles, nanostructured lipid carriers, and polymer-based nanocarriers [22,23]. In the following we will discuss some of these complexes.…”

The use of flavonoids in skin cancer prevention and treatment

“…Topical application of this compound to the skin of hairless SKH-1 mice greatly reduced the frequency and mean volume of UVBinduced tumours, compared to mice not treated with silymarin. Silymarin effectively protects the skin from all stages of photocarcinogenesis [23]. When applied topically, silibinin, the main component of Silymarin, induces MAPK cascades in UVB-induced skin cancers, thereby enhancing apoptotic death of the skin cancer cells [24].…”

Synthesis and application of polyethyleneimine and polyethylene glycol grafted on CoFe2O4/single‐walled carbon nanotubes as a delivery platform for silibinin: Loading experiments, modeling, and in‐vitro release studies

“…In‐vitro and in‐vivo studies with SB and its derivatives have revealed its remarkable inhibitory effects on various tumors, including the skin, triple‐negative breast, lung, colorectal, prostate, bladder, kidney, and liver 20 . This flavonoid imposes its anti‐neoplasm effects by inducing apoptosis, strengthening tumor suppressor factors, and stopping the cell cycle, as well as attenuating growth factors and mediators that promote proliferation and cell division of tumors 21 …”

“…20 This flavonoid imposes its antineoplasm effects by inducing apoptosis, strengthening tumor suppressor factors, and stopping the cell cycle, as well as attenuating growth factors and mediators that promote proliferation and cell division of tumors. 21 This study aims to prepare an SB-loaded CoFe 2 O 4 / SWCNT-PEI-PEG carrier to improve the water solubility of SB and its targeted delivery to the tumor. The affecting factors on the drug loading were systematically optimized.…”