Melanoma and Other Skin Cancers

Silymarin in Skin Cancer

Overview

Silymarin, a polyphenolic flavonoid complex extracted from milk thistle (Silybum marianum), has demonstrated significant anticancer and chemopreventive activity in skin-cancer preclinical models.

Research indicates its potential to inhibit tumour proliferation, induce apoptosis and cell cycle arrest, suppress angiogenesis, modulate immune responses, protect against ultraviolet (UV)-induced DNA damage, and reduce metastasis.

Studies investigate both melanoma and non-melanoma skin cancers (NMSCs), positioning silymarin as a promising adjunctive agent worthy of further clinical investigation.

How Silymarin May Work in Skin Cancer

Silymarin exerts its effects through multiple interconnected mechanisms. Key pathways identified in laboratory studies include:

• Inducing apoptosis via upregulation of Fas-associated death domain protein (FADD), cleavage of procaspase 8, and activation of caspase cascades—increasing pro-apoptotic Bax and decreasing anti-apoptotic Bcl-2 and Bcl-xL

• Promoting G1 or G2-M phase cell cycle arrest depending on cell type, with corresponding alterations in cyclins and cyclin-dependent kinases

• Inhibiting tumour cellular growth and angiogenesis by reducing vascular endothelial growth factor (VEGF) expression

• Modifying cellular immune response towards cancer through anti-inflammatory and immunomodulatory effects

• Inhibiting dermal gelatinolytic activity (matrix metalloproteinase activity) without impairing cell growth and viability

• Protecting against UVB-induced photodamage by modulating p53 and GADD45α levels, enhancing DNA repair, and reducing cyclobutane pyrimidine dimer (CPD) formation

• Targeting aberrant signalling pathways in non-melanoma skin cancers (NMSCs), including p53, MAPK, PI3K-Akt, and other survival pathways

• Inducing stress-activated protein kinase/jun NH₂-terminal kinase (SAPK/JNK) and p38 mitogen-activated protein kinase (p38 MAPK) activation in human epidermoid carcinoma cells

• Demonstrating strong antioxidant potential via reversal of reactive oxygen species (ROS)-induced cellular damages and upregulation of antioxidant enzymes (glutathione-S-transferase, quinine reductase, superoxide dismutase, catalase, GPX)

Findings by Skin Cancer Type

Melanoma

In human melanoma cell lines (A375 BRAF-mutated and Hs294t non-BRAF-mutated highly metastatic), silymarin has demonstrated:

• Dose-dependent reduction in cell viability in both in vitro and in vivo models

• Enhancement of either G0/G1 (in A375) or G2-M (in Hs294t) phase cell cycle arrest with corresponding alterations in cyclins and cyclin-dependent kinases

• Induction of apoptosis associated with reduced anti-apoptotic proteins (Bcl-2 and Bcl-xl), increased pro-apoptotic Bax, and caspase activation

• Significant inhibition (60%, P < 0.01) of BRAF-mutated A375 melanoma tumour xenograft growth with oral administration (500 mg/kg body weight twice weekly)

• Associated inhibition of cell proliferation, induction of apoptosis of tumour cells, alterations in cell cycle regulatory proteins, and reduced expression of tumour angiogenic biomarkers in xenograft tissues

• Induction of cell cycle arrest and inhibition of growth in human melanoma SK-MEL-5 and SK-MEL-28 cells in the G1 phase by blocking MEK1/2-RSK2 signalling

• Decrease in activation of transcriptional regulators of proliferation genes in melanoma, such as nuclear factor-kappaB, activator protein-1, and signal transduction and transcriptional activator 3

Non-Melanoma Skin Cancers (NMSCs)

In human epidermoid carcinoma A431 cells and mouse epidermis models, silymarin and its active component silibinin have shown:

• Growth inhibition of 30–74% (P < 0.01–0.001) and cell death of 7–42% in A431 cells at physiologically achievable concentrations (12.5–50 μM silibinin) in a dose- and time-dependent manner

• Apoptosis is the primary cell death response, with activation of stress-activated protein kinase/jun NH₂-terminal kinase (SAPK/JNK1/2) and p38 mitogen-activated protein kinase (p38 MAPK)

• Strong anticancer effect against established skin tumours, accompanied by tumour regression associated with decreased proliferation index and inhibition of MAPK/ERK1/2 signalling

• Significant inhibition of ornithine decarboxylase activity and mRNA expression, as well as TNF-α mRNA expression, was induced by structurally different tumour promoters (including free radical-generating compounds)

• Protection against UVB radiation-induced tumour initiation, tumour promotion, and complete carcinogenesis in SKH-1 hairless mouse skin

• Inhibition of TPA-caused induction of cyclooxygenase (COX) 2 and interleukin-1α expression in SENCAR mouse epidermis

• Impairment of epidermal growth factor receptor (EGFR)-mediated signalling as part of the skin cancer preventive mechanism

• Strong efficacy against all stages of photocarcinogenesis in NMSCs, including protection against UVB-induced genomic instability, tumour growth, and progression

• Enhancement of UVB-induced DNA damage repair by activating p53-dependent GADD45α in SKH-1 mouse skin and nucleotide excision repair (NER) pathway in normal human dermal fibroblasts

• Reduction of cellular levels of survivin (an important anti-apoptotic molecule) in UVB-induced skin tumours

• Protective effect against skin tumour-promoting agent benzoyl peroxide (BPO)-induced depletion of antioxidant enzymes such as superoxide dismutase (SOD), catalase, and GPX activity

• Potential to increase skin cellular levels of other antioxidant enzymes (glutathione-S-transferase and quinine reductase) involved in the removal of cellular reactive species

Cancer Stem Cell Targeting

While specific cancer stem cell (CSC) studies for silymarin in skin cancer are limited, mechanistic evidence supports potential effects:

• Silymarin’s inhibition of epithelial-to-mesenchymal transition (EMT) through modulation of β-catenin, ZEB1, and related pathways may impact cancer stem cell properties

• By suppressing gelatinolytic and metastatic activity (via MMP inhibition), silymarin may target stem-like cells responsible for invasion and metastasis

• The compound’s ability to induce apoptosis through multiple pathways (Fas/FasL, mitochondrial, p53-dependent) may overcome resistance mechanisms in cancer stem cell populations

• Silibinin’s effects on p53 and DNA repair pathways may target stem-like properties associated with treatment resistance and UV-induced damage

• In melanoma contexts, silymarin’s modulation of MEK/ERK and SAPK/JNK pathways may influence cancer stem cell-like phenotypes

Chemosensitisation and Combination Therapy

Silymarin demonstrates potential synergy with conventional skin cancer therapies:

• Silymarin’s antioxidant and anti-inflammatory properties may protect normal skin from chemotherapy-induced oxidative damage and inflammation

• By inhibiting angiogenesis and metastasis, silymarin may enhance the efficacy of standard therapies targeting primary tumour growth

• The compound’s immunomodulatory effects may enhance antitumor immune responses following chemotherapy-induced antigen release

• Silymarin-loaded inclusion complex-based gel systems have been developed as potential delivery systems for enhanced skin cancer treatment

• Combinations with other natural compounds (e.g., curcumin) have shown synergistic anti-proliferative effects in colorectal cancer models, suggesting potential for similar interactions in skin cancer

• Selenium combined with silybin has been shown to enhance therapeutic effects in other cancer models, warranting investigation in skin cancer contexts

Radiotherapy and Phototherapy Support

Silymarin shows particular promise in the context of UV and phototherapy:

• Silymarin’s protective efficacy against UVB-induced photodamage is well-established through p53 and GADD45α modulation, DNA repair enhancement, and antioxidant effects

• The compound prevents UVB-induced accumulation of cells in the S phase of the cell cycle, allowing time for DNA repair before replication

• In p53-sufficient cells, silibinin pretreatment significantly enhances the protective effect against UVB-induced apoptosis, while this effect is diminished in p53-deficient contexts

• Silymarin dramatically reduces cyclobutane pyrimidine dimer (CPD) formation in UVB-exposed epidermis (60% reduction with pretreatment, 43% with post-treatment)

• By activating p53-dependent GADD45α and nucleotide excision repair (NER) pathways, silymarin enhances the repair of UVB-induced DNA damage in normal skinin

• The compound’s ability to kill UVA-mutated keratinocytes while protecting normal cells suggests potential for selective removal of photo-aged and premalignant cells

• Silymarin’s anti-inflammatory effects may mitigate radiation-induced dermatitis in radiotherapy settings

• Clinical trials evaluating topical or oral silymarin during skin cancer radiotherapy or photodynamic therapy are warranted, given its safety profile and mechanistic plausibility

Practical Interpretation for Patients

Silymarin is not a treatment for skin cancer, but research suggests it may offer many supportive benefits as an adjunct:

• It may inhibit tumour proliferation and induce apoptosis in both melanoma and non-melanoma skin cancer cells through multiple pathways

• It shows potential to arrest cell cycle progression and reduce angiogenic and metastatic potential

• It appears to protect against UV-induced DNA damage and enhance repair mechanisms, particularly relevant for prevention and adjunctive use

• It has demonstrated favourable safety profiles in preclinical and clinical studies, with no significant liver or kidney toxicity observed at therapeutic doses

• Any consideration should involve discussion with oncology or dermatology professionals regarding timing (e.g., avoiding high-dose antioxidants during radiotherapy if pro-oxidant tumour effects are desired) and formulation (standardised extracts vs. nanoparticles vs. topical gels)

• Silymarin is best understood as a potential complement to conventional care, used in discussion with your treating team, with particular relevance for UV protection and chemoprevention strategies

References for Silymarin in Skin Cancer

Exploring the multifaceted effects of silymarin on melanoma (2024): https://www.sciencedirect.com/science/article/abs/pii/S1773224724006191

Silymarin: a promising modulator of apoptosis and survival signaling ... (2025): https://pmc.ncbi.nlm.nih.gov/articles/PMC11751200/

Formulation and Evaluation of a Silymarin Inclusion Complex-Based ... (2025): https://pubs.acs.org/doi/abs/10.1021/acsomega.4c09614

Silymarin inhibits growth and causes regression of established skin ... (2002): https://academic.oup.com/carcin/article/23/3/499/2390222

Natural products as therapeutics for malignant melanoma - PMC (2025): https://pmc.ncbi.nlm.nih.gov/articles/PMC12417409/

Mechanisms and preclinical efficacy of silibinin in preventing skin ... (2005): https://pubmed.ncbi.nlm.nih.gov/16084079/

Silibinin, found in milk thistle, protects against UV-induced skin cancer (2013): https://ecancer.org/en/news/3765-silibinin-found-in-milk-thistle-protects-against-uv-induced-skin-cancer

Silibinin and non-melanoma skin cancers - PMC (2020): https://pmc.ncbi.nlm.nih.gov/articles/PMC7340873/

Complementary and Alternative Approaches to Skin Cancer (2025): https://www.jintegrativederm.org/doi/10.64550/joid.r82q4h22

Engineering SnO₂ nanoparticles for effective silymarin ... (2025): https://www.sciencedirect.com/science/article/pii/S294982952500186X

Silibinin, found in milk thistle, protects against UV-induced skin cancer (2026): https://www.sciencedaily.com/releases/2013/01/130130143636.htm

Silymarin inhibits melanoma cell growth both in vitro and in ... (2015): https://pubmed.ncbi.nlm.nih.gov/25174976/

Silibinin prevents ultraviolet B radiation-induced epidermal ... (2011): https://pmc.ncbi.nlm.nih.gov/articles/PMC3384068/

Protective Effects of Silymarin Against Photocarcinogenesis in ... (2011): https://academic.oup.com/jnci/article/89/8/556/2526883

Silymarin Protects Epidermal Keratinocytes from Ultraviolet ... (2011): https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0021410

Silibinin treatment protects human skin cells from UVB ... (2021): https://www.sciencedirect.com/science/article/abs/pii/S1011134421000257

Formulation and Evaluation of a Silymarin Inclusion Complex ... (2025): https://pubs.acs.org/doi/10.1021/acsomega.4c09614

Silymarin inhibits dermal gelatinolytic activity and reduces ... (2023): https://www.tandfonline.com/doi/full/10.1080/14786419.2024.2347452

Insights into its clinical impact in various types of cancer (2019): https://research.uees.edu.ec/en/publications/silymarin-antiproliferative-and-apoptotic-effects-insights-into-i-2/

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