Why vitamin D for cancer patients?

Vitamin D signaling and melanoma: role of vitamin D and its receptors in melanoma progression and management

Ultraviolet B (UVB), in addition to having carcinogenic activity, is required for the production of vitamin D3 (D3) in the skin which supplies >90% of the body's requirement. Vitamin D is activated through hydroxylation by 25-hydroxylases (CYP2R1 or CYP27A1) and 1α-hydroxylase (CYP27B1) to produce 1,25(OH)₂D3, or through the action of CYP11A1 to produce mono-di- and trihydroxy-D3 products that can be further modified by CYP27B1, CYP27A1, and CYP24A1. The active forms of D3, in addition to regulating calcium metabolism, exert pleiotropic activities, which include anticarcinogenic and anti-melanoma effects in experimental models, with photoprotection against UVB-induced damage. These diverse effects are mediated through an interaction with the vitamin D receptor (VDR) and/or as most recently demonstrated through action on retinoic acid orphan receptors (ROR)α and RORγ. With respect to melanoma, low levels of 25(OH)D are associated with thicker tumors and reduced patient survival. Furthermore, single-nucleotide polymorphisms of VDR and the vitamin D-binding protein (VDP) genes affect melanomagenesis or disease outcome. Clinicopathological analyses have shown positive correlation between low or undetectable expression of VDR and/or CYP27B1 in melanoma with tumor progression and shorter overall (OS) and disease-free survival (DFS) times. Paradoxically, this correlation was reversed for CYP24A1 (inactivating 24-hydroxylase), indicating that this enzyme, while inactivating 1,25(OH)₂D3, can activate other forms of D3 that are products of the non-canonical pathway initiated by CYP11A1. An inverse correlation has been found between the levels of RORα and RORγ expression and melanoma progression and disease outcome. Therefore, we propose that defects in vitamin D signaling including D3 activation/inactivation, and the expression and activity of the corresponding receptors, affect melanoma progression and the outcome of the disease. The existence of multiple bioactive forms of D3 and alternative receptors affecting the behavior of melanoma should be taken into consideration when applying vitamin D management for melanoma therapy.

Sun exposure and melanoma prognostic factors

Previous studies have reported an association between sun exposure and the increased survival of patients with cutaneous melanoma (CM). The present study analyzed the association between ultraviolet (UV) light exposure and various prognostic factors in the Italian Clinical National Melanoma Registry. Clinical and sociodemographic features were collected, as well as information concerning sunbed exposure and holidays with sun exposure. Analyses were performed to investigate the association between exposure to UV and melanoma prognostic factors. Between December 2010 and December 2013, information was obtained on 2,738 melanoma patients from 38 geographically representative Italian sites. A total of 49% of the patients were >55 years old, 51% were men, 50% lived in the north of Italy and 57% possessed a high level of education (at least high school). A total of 8 patients had a family history of melanoma and 56% had a fair phenotype (Fitzpatrick skin type I or II). Of the total patients, 29% had been diagnosed with melanoma by a dermatologist; 29% of patients presented with a very thick melanoma (Breslow thickness, >2 mm) and 25% with an ulcerated melanoma. In total, 1% of patients had distant metastases and 13% exhibited lymph node involvement. Holidays with sun exposure 5 years prior to CM diagnosis were significantly associated with positive prognostic factors, including lower Breslow thickness (P<0.001) and absence of ulceration (P=0.009), following multiple adjustments for factors such as sociodemographic status, speciality of doctor performing the diagnosis and season of diagnosis. Sunbed exposure and sun exposure during peak hours of sunlight were not significantly associated with Breslow thickness and ulceration. Holidays with sun exposure were associated with favorable CM prognostic factors, whereas no association was identified between sunbed use and sun exposure during peak hours of sunlight with favorable CM prognostic factors. However, the results of the present study do not prove a direct causal effect of sun exposure on melanoma prognosis, as additional confounding factors, including vitamin D serum levels, may have a role.

Review of natural compounds for potential skin cancer treatment

Most anti-cancer drugs are derived from natural resources such as marine, microbial and botanical sources. Cutaneous malignant melanoma is the most aggressive form of skin cancer, with a high mortality rate. Various treatments for malignant melanoma are available, but due to the development of multi-drug resistance, current or emerging chemotherapies have a relatively low success rates. This emphasizes the importance of discovering new compounds that are both safe and effective against melanoma. In vitro testing of melanoma cell lines and murine melanoma models offers the opportunity for identifying mechanisms of action of plant derived compounds and extracts. Common anti-melanoma effects of natural compounds include potentiating apoptosis, inhibiting cell proliferation and inhibiting metastasis. There are different mechanisms and pathways responsible for anti-melanoma actions of medicinal compounds such as promotion of caspase activity, inhibition of angiogenesis and inhibition of the effects of tumor promoting proteins such as PI3-K, Bcl-2, STAT3 and MMPs. This review thus aims at providing an overview of anti-cancer compounds, derived from natural sources, that are currently used in cancer chemotherapies, or that have been reported to show anti-melanoma, or anti-skin cancer activities. Phytochemicals that are discussed in this review include flavonoids, carotenoids, terpenoids, vitamins, sulforaphane, some polyphenols and crude plant extracts.