Evaluation of a Ultraviolet B Light Emitting Diode (LED) for Producing Vitamin D3 in Human Skin

AIM

A commercially available light emitting diode (LED) that transmitted narrow band ultraviolet B (UVB) radiation was evaluated for its efficacy and efficiency to produce vitamin D₃ in human skin.

MATERIALS AND METHODS

Human skin samples were obtained from surgical procedures. The LED had peak emission wavelength of 295 nm. Skin samples were exposed to the UVB-LED for varying times and then were analyzed by high-pressure liquid chromatography (HPLC) to determine the vitamin D₃ content.

RESULTS

There was a statistically significant time- and dose-dependent increase in the percent of 7-dehydrocholesterol that was converted to vitamin D₃ in the skin type II samples; 1.3%±0.5, 2.3%±0.6 and 4.5%±1.67 after exposure to 0.75 (11.7 mJ/cm²), 1.5 (23.4 mJ/cm²) and 3 (46.8 mJ/cm²) minimal erythemal doses (MEDs), respectively.

CONCLUSION

The UVB-LED was effective and efficient in generating vitamin D₃ in human skin, in vitro. The amount of vitamin D₃ production increased in a dose-dependent fashion with increased UVB energy. UVB-LEDs can be developed for devices that can efficiently produce vitamin D₃ in human skin.

Evaluation of Effectiveness of Ultraviolet Emitting Lamps on the Cutaneous Production of Vitamin D3: Relationship of the Lamps Vitamin D3 Producing Potential to the Production of 8-Hydroxy-2'-Deoxyguanosine and Nitric Oxide

BACKGROUND/AIM

To assess the effectiveness of three UV emitting lamps on the cutaneous production of vitamin D₃, a marker of DNA damage and nitric oxide production in human skin.

MATERIALS AND METHODS

Human skin samples (skin types II, III and IV) obtained from surgery were exposed to three different UV emitting lamps for varying times and then extracted and chromatographed to determine the vitamin D₃ content. The skin samples exposed to the 3 UV emitting lamps were also evaluated for 8-hydroxy-2'-deoxyguanosine (a marker of DNA damage) and nitric oxide production.

RESULTS

It was observed that the spectral output of the 3 lamps had different effects on the cutaneous production of vitamin D₃, 8-hydroxy-2'-deoxyguanosine and nitric oxide production. One lamp demonstrated optimal production of vitamin D₃ with the least amount of DNA damage and intermediate production of nitric oxide suggesting that it could be developed into a device for treating vitamin D deficiency.

CONCLUSION

The spectral output of the experimental UVB emitting lamps significantly influenced the cutaneous production of vitamin D₃ 8-hydroxy-2'-deoxyguanosine and nitric oxide.

Effect of dietary vitamin D and calcium on the growth of androgen-insensitive human prostate tumor in a murine model

Vitamin D deficiency has been associated with increased risk of prostate cancer (PC) in epidemiologic and prospective studies. An association has also been made between high dietary calcium and increased PC risk. In this study, we evaluated the effect of dietary vitamin D and calcium on the growth of human androgen-insensitive prostate tumor in an athymic mouse model. We observed highest tumor growth in the normal calcium - vitamin D-deficient group, while tumor growth between the normal calcium - vitamin D-sufficient, high calcium - vitamin D-sufficient and high calcium - vitamin D-deficient diet-groups did not significantly differ but was significantly lower than that in the normal calcium - vitamin D-deficient group. Our results suggest an important role of dietary vitamin D as a preventive agent in androgen-insensitive PC.

Abstract A41: Effect of dietary vitamin D3 and calcium on the growth of androgeninsensitive human prostate tumor in a murine model

Vitamin D deficiency has been associated with increased risk of prostate cancer in epidemiologic and prospective studies. An association has also been made between high dietary calcium and increased prostate cancer risk. Previous studies have demonstrated that normal prostate cells and some prostate cancer cells have the ability to convert 25(OH)D to 1α,25(OH)2D. This ability along with epidemiological evidence correlating an inverse relationship between serum 25(OH)D levels and prostate cancer risk suggests that vitamin D may be important for prostate cancer prevention. The effect of dietary vitamin D and calcium on the growth of human androgen-insensitive prostate tumor in an athymic mouse model was evaluated. Three factors were considered in evaluating the role of dietary calcium and vitamin D on prostate tumor in our mice model: tumor-growth, elevation of serum calcium and overall growth of the animals (body weight). Immunohistochemical staining and Real Time PCR analysis were performed on tumors to elucidate the molecular mechanism(s) involved in vitamin D regulation of prostate cancer. Tumor-growth was highest in normal calcium, vitamin D deficient diet group (381±59 mm3) while growth in normal calcium, vitamin D sufficient (179±36 mm3), high calcium, vitamin D sufficient (199±25 mm3) and deficient (204±43 mm3) diets were not significantly different from one another. The normal calcium, vitamin D deficient diet had mice that were normo-calcemic compared to the other diet groups though there was no significant difference between groups for the weights of the animals. Proliferative (Ki67) and apoptotic (Caspase 3) staining revealed no significant difference between vitamin D sufficient and deficient diet groups. Additional staining for p21 did not show any difference among the diet groups. Gene analysis for p21, p27 and p53 did not demonstrate altered transcriptional activity in vitamin D sufficient groups. Bax and bcl-2 mRNA expression were both increased in the high calcium, vitamin D deficient diet group. The difference in tumor growth between the normal calcium, vitamin D deficient diet and the other diets suggest an important role of dietary vitamin D as a preventive agent in androgen-insensitive prostate cancer. More in vivo studies are needed to understand the molecular mechanism(s) behind vitamin D's antitumorigenic effects.

Citation Format: Rahul Ray, Mara Banks, Hilal Abuzahra, Kelly S. Persons, Vikram J. Eddy, James R. Lambert, Michael F. Holick. Effect of dietary vitamin D3 and calcium on the growth of androgeninsensitive human prostate tumor in a murine model [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr A41.

Internalization of a C17α-alkynylestradiol-porphyrin conjugate into estrogen receptor positive MCF-7 breast cancer cells

We hypothesized that expression of nuclear estrogen receptor (ER) in hormone-sensitive breast cancer cells could be harnessed synergistically with the tumor-accumulating effect of porphyrins to selectively deliver estrogen-porphyrin conjugates into breast tumor cells, and preferentially kill tumor cells upon exposure to visible light. In this study we synthesized a conjugate of C(17α)-alkynylestradiol and pyropheophorbide and demonstrated that this conjugate is internalized by ER-positive MCF-7 cells while pyropheophorbide did not, suggesting an ER-mediated uptake and internalization of the conjugate by incipient nuclear ER in MCF-7 cells. This study is a direct demonstration of our hypothesis about ER-mediated internalization of estrogen-porphyrin conjugates.

A vitamin D receptor-alkylating derivative of 1α,25-dihydroxyvitamin D3 inhibits growth of human kidney cancer cells and suppresses tumor growth

1,25-Dihydroxyvitamin D₃ [1,25(OH)₂D₃] has shown strong promise as an antiproliferative agent in several malignancies, yet its therapeutic use has been limited by its toxicity leading to search for analogues with antitumor property and low toxicity. In this study, we evaluated the in vitro and in vivo properties of 1,25-dihydroxyvitamin D₃-3-bromoacetate [1,25(OH)₂D₃-3-BE], an alkylating derivative of 1,25(OH)₂D₃, as a potential therapeutic agent for renal cancer. Dose response of 1,25(OH)₂D₃-3-BE in 2 kidney cancer cell lines was evaluated for its antiproliferative and apoptotic properties, and mechanisms were evaluated by Western blot and FACS analyses. Therapeutic potential of 1,25(OH)₂D₃-3-BE was assessed both by determining its stability in human serum and by evaluating its efficacy in a mouse xenograft model of human renal tumor. We observed that 1,25(OH)₂D₃-3-BE is significantly more potent than an equivalent concentration of 1,25(OH)₂D₃ in inhibiting growth of A498 and Caki 1 human kidney cancer cells. 1,25(OH)₂D₃-3-BE-mediated growth inhibition was promoted through inhibition of cell-cycle progression by downregulating cyclin A and induction of apoptosis by stimulating caspase activity. Moreover, 1,25(OH)₂D₃-3-BE strongly inhibited Akt phosphorylation and phosphorylation of its downstream target, caspase-9. 1,25(OH)₂D₃-3-BE seemed to be stable in human serum. In xenograft mouse model of human renal tumor, 1,25(OH)₂D₃-3-BE was more potent at reducing tumor size than 1,25(OH)₂D₃, which was accompanied by an increase in apopotosis and reduction of cyclin A staining in the tumors. These results suggest a translational potential of this compound as a therapeutic agent in renal cell carcinoma. Data from this study and extensive studies of vitamin D for the prevention of many malignancies support the potential of 1,25(OH)₂D₃-3-BE for preventing renal cancer and the development of relevant in vivo prevention models for assessing this potential, which do not exist at present.

Anti-growth effect of 1,25-dihydroxyvitamin D3-3-bromoacetate alone or in combination with 5-amino-imidazole-4-carboxamide-1-beta-4-ribofuranoside in pancreatic cancer cells

1,25-Dihydroxyvitamin D(3)-3-bromoacetate (1,25(OH)(2)D(3)-3-BE) is a vitamin D receptor-alkylating derivative of 1,25(OH)(2)D(3). The strong dose-dependent antiproliferative and apoptotic effects of this compound in androgen-sensitive and androgen-insensitive prostate cancer cells have been reported. In this communication, it is reported that 1,25(OH)(2)D(3)-3-BE strongly inhibits the growth of several pancreatic cancer cell lines. This effect is further accentuated by combination with 5-amino-imidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR), an activator of AMP-activated protein kinase (AMPK)/acetyl-Co-enzyme A carboxylase (ACC) phosphorylation pathways and an inhibitor of Akt phosphorylation. It was observed that the anti-growth property of 1,25(OH)(2)D(3)-3-BE, either alone or in combination with AICAR resulted in the inhibition of Akt phosphorylation in BxPC-3 cells. In conclusion, 1,25(OH)(2)D(3)-3-BE displays a strong therapeutic potential, alone and in combination with AICAR, in pancreatic cancer.

Abstract 5533: Anti-proliferative and anti-tumor effects of a novel vitamin D derivative, either alone or in a liposomal formulation in malignancies of kidney, pancreas and prostate

1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has well-known potential in cancer-therapy; but such a potential is marred by its severe toxicity in pharmacological doses. 1α,25-dihydroxyvitamin D3-3-bromoacetate (1,25(OH)2D3-3-BE) is a novel derivative of 1,25(OH)2D3 which enables covalent attachment of 1,25(OH)2D3 inside the ligand-binding pocket of nuclear vitamin D receptor, thus increasing the half-life of 1,25(OH)2D3 and potentially reducing its therapeutic dose with less toxicity. We have observed that 1,25(OH)2D3-3-BE strongly hinders the growth of cells representing malignancies of prostate (androgen-sensitive and androgen-insensitive), pancreas and kidney. However, growth of normal kidney and prostate cells is not affected by this compound. Inhibition of cell-growth by 1,25(OH)2D3-3-BE involves hindrance to cell-cycling, and enhancement of apoptosis and autophagy; and includes several mechanisms involving VDR-mediated nuclear pathway and inhibition of Akt-phophorylation. We have also observed that 1,25(OH)2D3-3-BE strongly inhibits the growth of prostate and renal tumors in mouse xenograft models. In anticipation of its therapeutic potential we prepared a liposomal formulation of 1,25(OH)2D3-3-BE to enhance its efficacy further by potentially preventing its premature degradation and tumor-targeting. We report that liposomal 1,25(OH)2D3-3-BE is a significantly stronger growth-inhibiting compound than naked 1,25(OH)2D3-3-BE in prostate, kidney and pancreatic cancer cells. This property is also manifested in a mouse xenograft model of androgen-insensitive prostate tumor. In summary, 1,25(OH)2D3-3-BE and its liposomal formulation demonstrate a strong translational therapeutic potential in cancers of kidney, pancreas and prostate.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5533.

Fish oil enhances the antiproliferative effect of 1alpha,25-dihydroxyvitamin D3 on liver cancer cells

BACKGROUND

Laboratory and epidemiological studies have indicated that 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and dietary omega 3 (omega3)-polyunsaturated fatty acids (PUFAs) are capable of inhibiting the proliferation of various cancer cells.

MATERIALS AND METHODS

Human hepatoblastoma cells (HepG2) were treated with 1alpha,25(OH)2D3 and fish oil alone and in combination. Cell proliferation was measured either by the uptake of [3H]-thymidine into DNA or by counting the cell numbers using a hemocytometer.

RESULTS

The HepG2 cell proliferation was inhibited by 1alpha,25(OH)2D3 and fish oil in a dose-dependent manner. The lowest effective concentration of 1alpha,25(OH)2D3 was 10(-7) M and 10(-8) M using the [3H]-thymidine incorporation method and the cell counting method, respectively. Fish oil also caused a significant inhibition in HepG2 cell proliferation at 25 microg/mL. When HepG2 cells were treated with 1alpha,25(OH)2D3 in combination with fish oil, it was found that fish oil increased the antiproliferative effect of 1alpha,25(OH)2D3 on HepG2 cell growth compared to treatment with 1alpha,25(OH)2D3 alone.

CONCLUSION

1alpha,25(OH)2D3 could be used to treat hepatocellular carcinoma (HCC). However, the major side-effect of hypercalcemia limits its use. An enhanced 1alpha,25(OH)2D3-induced inhibition of HepG2 cell proliferation in the presence of PUFAs in the form of fish oil suggests that a lower concentration of 1alpha,25(OH)2D3 could be used to treat hepatocellular carcinoma in the presence of PUFAs to decrease the risk of hypercalcemia caused by high concentrations of 1alpha,25(OH)2D3.

Evaluation of 19-nor-2alpha-(3-hydroxypropyl)-1alpha,25-dihydroxyvitamin D3 as a therapeutic agent for androgen-dependent prostate cancer

The high incidence of prostate cancer and lack of an effective, long-term treatment for metastatic disease highlights the need for more potent non-calcemic vitamin D analogs as potential alternative or combinational prostate cancer therapies. Among the analogs, 19-nor-1alpha,25-dihydroxyvitamin D2 (19-nor-1alpha,25(OH)2D2) known as paricalcitol or Zempler, has less calcemic effects and an equipotential activity as 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) in several in vivo and in vitro systems. It was recently demonstrated that a modified analog of paricalcitol, 19-nor-2alpha-(3-hydroxypropyl)-1alpha,25-dihydroxyvitamin D3 (MART-10) compared to 1alpha,25(OH)2D3 was more effective in inhibiting proliferation of an immortalized normal prostate cell line (PZ-HPV-7) (1,000-fold) and invasion of PC-3 prostate cancer cells (10-fold). In this study, the effects of MART-10 and 1alpha,25(OH)2D3 on proliferation, vitamin D receptor transactivation, vitamin D-binding protein (DBP) binding, CYP24A1 (24-OHase) substrate hydroxylation kinetics, and induction of CYP24A1 gene expression were compared in an androgen-dependent prostate cancer cell model, LNCaP. The results demonstrated that MART-10 was 1,000-fold more active than 1alpha,25(OH)2D3 in inhibiting LNCaP cell proliferation. MART-10 was more active than 1alpha,25(OH)2D3 in up-regulating a vitamin D receptor-responsive Luciferase construct and inducing CYP24A1 gene expression in LNCaP prostate cancer cells. In addition, MART-10 has a lower affinity for DBP and less substrate degradation by CYP24A1 compared to 1alpha,25(OH)2D3, indicating that MART-10 has more bioavailability and a longer half-life. Thus, these data suggest that MART-10 may be a potential candidate as a therapeutic agent for prostate cancer, especially for patients who fail in conventional therapies.

Covalent labeling of nuclear vitamin D receptor with affinity labeling reagents containing a cross-linking probe at three different positions of the parent ligand: structural and biochemical implications

Structure-functional characterization of vitamin D receptor (VDR) requires identification of structurally distinct areas of VDR-ligand-binding domain (VDR-LBD) important for biological properties of 1alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)). We hypothesized that covalent attachment of the ligand into VDR-LBD might alter 'surface structure' of that area influencing biological activity of the ligand. We compared anti-proliferative activity of three affinity alkylating derivatives of 1,25(OH)(2)D(3) containing an alkylating probe at 1,3 and 11 positions. These compounds possessed high-affinity binding for VDR; and affinity labeled VDR-LBD. But, only the analog with probe at 3-position significantly altered growth in keratinocytes, compared with 1,25(OH)(2)D(3). Molecular models of these analogs, docked inside VDR-LBD tentatively identified Ser237 (helix-3: 1,25(OH)(2)D(3)-1-BE), Cys288 (beta-hairpin region: 1,25(OH)(2)D(3)-3-BE,) and Tyr295 (helix-6: 1,25(OH)(2)D(3)-11-BE,) as amino acids that are potentially modified by these reagents. Therefore, we conclude that the beta-hairpin region (modified by 1,25(OH)(2)D(3)-3-BE) is most important for growth inhibition by 1,25(OH)(2)D(3), while helices 3 and 6 are less important for such activity.

Prostate 25-hydroxyvitamin D-1alpha-hydroxylase is up-regulated by suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor

Prostatic 25-hydroxyvitamin D-1alpha-hydroxylase (1alpha-OHase) is up-regulated by epidermal growth factor (EGF) and down-regulated by 1alpha,25-dihydroxyvitamin D [1alpha,25(OH)2D] at the promoter level in an autocrine/paracrine fashion, suggesting that local production of 1alpha,25(OH)2D could provide an important cell growth regulatory mechanism. Gene expressions depend on the acetylation status of the histone tails of chromatin, which is regulated by histone acetyltransferases and histone deacetylases (HDAC). A number of HDAC inhibitors, including suberolylanilide hydroxamic acid (SAHA), can inhibit tumor growth in vitro and in vivo. Moreover, SAHA increases the expression of genes which modulate cell cycle progression, tumor suppression, differentiation and apoptosis. Therefore, whether SAHA might also regulate 1alpha-OHase activity in PZ-HPV-7 prostate cells was investigated. SAHA at 10 microM up-regulated 1alpha-OHase activity approximately two-fold as analyzed by the formation of 3H-1alpha,25(OH)2D3 from 3H-25-hydroxyvitamin D3 using high performance liquid chromatography. SAHA (10 microM) also stimulated 1alpha-OHase mRNA expression as measured by real-time polymerase chair reaction, and promoter activity determined by luciferase reporter gene assay. The findings suggest that another important action of SAHA may be to up-regulate the expression of the 1alpha-OHase gene that controls the synthesis of 1alpha,25(OH)2D which in turn regulates prostate growth and differentiation in an autocrine/paracrine fashion.

Mechanistic and pharmacodynamic studies of a 25-hydroxyvitamin D3 derivative in prostate cancer cells

1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), the biologically active form of vitamin D has strong antiproliferative effects in cancer cells. But it is highly toxic at therapeutic doses. We have observed that 25-hydroxyvitamin D(3)-3-bromoacetate (25-OH-D(3)-3-BE), a derivative of 25-hydroxyvitamin D(3), the pro-hormonal form of 1,25(OH)(2)D(3) has strong growth-inhibitory and proapoptotic properties in hormone-sensitive and hormone-refractory prostate cancer cells. In the present investigation we demonstrate that the antiproliferative effect of 25-OH-D(3)-3-BE is predominantly mediated by VDR in ALVA-31 prostate cancer cells. In other mechanistic studies we show that the proapoptotic property of 25-OH-D(3)-3-BE is related to the inhibition of phosphorylation of Akt, a pro-survival protein. Furthermore, we carried out cellular uptake and serum stability studies of 25-OH-D(3)-3-BE to demonstrate potential therapeutic applicability of 25-OH-D(3)-3-BE in hormone-sensitive and hormone-insensitive prostate cancer.

Evaluation of C-2-substituted 19-nor-1alpha,25-dihydroxyvitamin D3 analogs as therapeutic agents for prostate cancer

1alpha,25-Dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) is known to inhibit the proliferation and invasiveness of prostate cancer cells. However, 1alpha,25(OH)(2)D(3) can cause hypercalcemia and is not suitable as a therapeutic agent. 19-Nor-vitamin D derivatives are known to be less calcemic when administered systemically. In order to develop more potent anti-cancer agents with less calcemic side effect, we therefore utilized (3)H-thymidine incorporation as an index for cell proliferation and examined the antiproliferative activities of nine C-2-substituted 19-nor-1alpha,25(OH)(2)D(3) analogs in the immortalized PZ-HPV-7 normal prostate cell line. Among the nine analogs we observed that the substitution with 2alpha- or 2beta-hydroxypropyl group produced two analogs having antiproliferative potency that is approximately 500- to 1000-fold higher than 1alpha,25(OH)(2)D(3). The (3)H-thymidine incorporation data were supported by the cell counting data after cells were treated with 1alpha,25(OH)(2)D(3), 19-nor-2alpha-(3-hydroxypropyl)-1alpha,25(OH)(2)D(3) or 19-nor-2beta-(3-hydroxypropyl)-1alpha,25(OH)(2)D(3) for 7 days. 19-Nor-2alpha-(3-hydroxypropyl)-1alpha,25(OH)(2)D(3) and 19-nor-2beta-(3-hydroxypropyl)-1alpha,25(OH)(2)D(3) were also shown to be about 10-fold more active than 1alpha,25(OH)(2)D(3) in cell invasion studies using prostate cancer cells. In conclusion, a substitution at the C-2 position of 19-nor-1alpha,25(OH)(2)D(3) molecule with a hydroxypropyl group greatly increased the antiproliferative and anti-invasion potencies. Thus, these two analogs could be developed to be effective therapeutic agents for treating early and late stages of prostate cancer.

An evaluation of the vitamin D3 content in fish: Is the vitamin D content adequate to satisfy the dietary requirement for vitamin D?

It has been suggested that the major source of vitamin D should come from dietary sources and not sun exposure. However, the major fortified dietary source of vitamin D is milk which often does not contain at least 80% of what is stated on the label. Fish has been touted as an excellent source of vitamin D especially oily fish including salmon and mackerel. Little is known about the effect of various cooking conditions on the vitamin D content in fish. We initiated a study and evaluated the vitamin D content in several species of fish and also evaluated the effect of baking and frying on the vitamin D content. Surprisingly, farmed salmon had approximately 25% of the vitamin D content as wild salmon had. The vitamin D content in fish varied widely even within species. These data suggest that the tables that list the vitamin D content are out-of-date and need to be re-evaluated.

Vitamin D metabolism in human prostate cells: implications for prostate cancer chemoprevention by vitamin D

BACKGROUND

Prostate cells can produce 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) from 25-hydroxyvitamin D3 (25(OH)D3) to regulate their own growth. Here, the questions of whether prostate cells express vitamin D-25-hydroxylase (25-OHase) and can convert vitamin D3 to 1alpha,25(OH)2D3 were investigated.

MATERIALS AND METHODS

Protein and receptor binding assays were used to determine 25(OH)D3 and 1alpha,25(OH)2D3, respectively. Measurements of proliferation by 3H-thymidine incorporation, and 1alpha,25(OH)2D-responsive gene expression by real-time qPCR and by Western blot were used as functional assays for the presence of 25-OHase activity.

RESULTS

Prostate cells metabolized vitamin D3 to 1alpha,25(OH)2D3. Vitamin D3 up-regulated 25(OH)D-24R-hydroxylase and IGFBP3, two 1alpha,25(OH)2D-responsive genes, in prostate cells. CYP2R1 was the major form of 25-OHase expressed in normal and cancerous prostate cells as determined by qPCR.

CONCLUSION

The autocrine synthesis of 1alpha,25(OH)2D3 from vitamin D3 suggests that maintaining adequate levels of serum vitamin D could be a safe and effective chemo-preventive measure to decrease the risk of prostate cancer.

1alpha,25-Dihydroxyvitamin D3-3beta-(2)-bromoacetate, an affinity labeling derivative of 1alpha,25-dihydroxyvitamin D3 displays strong antiproliferative and cytotoxic behavior in prostate cancer cells

In this report we describe that 1,25(OH)(2)D(3)-3-BE, a VDR-affinity labeling analog of 1,25(OH)(2)D(3), showed strong and dose-dependent growth-inhibitory effect in several epithelial cells, i.e., keratinocytes (primary cells), MCF-7 breast cancer, PC-3, and LNCaP prostate cancer and PZ-HPV-7 immortalized normal prostate cell-lines. Furthermore, 10(-6) M of 1,25(OH)(2)D(3)-3-BE induced apoptosis specifically in LNCaP and PC-3 cells; and the effect was much less pronounced at lower doses. We also showed that the effect (of 1,25(OH)(2)D(3)-3-BE) was not due to probable degradation (hydrolysis) of 1,25(OH)(2)D(3)-3-BE or random interaction of this molecule with cellular proteins. Tissue- or cell-specific action of 1,25(OH)(2)D(3) and its mimics is not common due to the ubiquitous nature of VDR. Furthermore, variable effects of 1,25(OH)(2)D(3) and its analogs in various cell-lines potentially limits their application as anticancer agents. We showed that 1,25(OH)(2)D(3)-3-BE displayed similar growth-inhibitory and cytotoxic activities towards androgen sensitive LNCaP and androgen-independent PC-3 cell-lines. Therefore, these results raise the possibility that 1,25(OH)(2)D(3)-3-BE or similar VDR-cross linking analogs of 1,25(OH)(2)D(3) might be considered for further development as potential candidates for prostate cancer.

An evaluation of the biologic activity and vitamin D receptor binding affinity of the photoisomers of vitamin D3 and previtamin D3

Skin is in the site of previtamin D3 and vitamin D3 synthesis and their isomerization in response to ultraviolet irradiation. At present, little is known about the function of the photoisomers of previtamin D3 and the vitamin D3 in skin cells. In this study we investigated the antiproliferative activity of the major photoisomers and their metabolites in the cultured human keratinocytes by determining their influence on 3H-thymidine incorporation into DNA. Our results demonstrated at both 10(-8) and 10(-6) M in a dose-dependent manner. Lumisterol, tachysterol3, 5,6-trans-vitamin D3, and 25-hydroxy-5,6-trans-vitamin D3 only induced significant inhibition at 10(-6) M. 25-Hydroxytachysterol3 was approximately 10- to 100-fold more active than tachysterol3. 7-Dehydrocholesterol was not active even at 10(-6) M. The dissociation constants of vitamin D receptor (VDR) for 25-hydroxytachysterol3, 25-hydroxy-5,6-trans-vitamin D3, and 5,6-trans-vitamin D3 were 22, 58, and 560 nM, respectively. The dissociation constants for 7-dehydrocholesterol, tachysterol, and lumisterol were greater than 20 microM. In conclusion, vitamin D3, its photoisomers and the photoisomers of previtamin D3 have antiproliferative activity in cultured human keratinocytes. However, the antiproliferative activity did not correlate with their binding affinity for VDR. The results suggest that some of the photoproducts may be metabolized to their 25-hydroxylated and 1 alpha,25-dihydroxylated counterparts before acting on VDR. Alternatively, a different receptor may recognize these photoproducts or another mechanism may be involved in modulating the antiproliferative activity of the photoisomers examined.

Increased PKC activity in cultured human keratinocytes and fibroblasts after treatment with 1 alpha, 25-dihydroxyvitamin D3

1 alpha,25-Dihydroxyvitamin D3 (10(-12) M to 10(-8) M) caused a dose dependent increase in PKC activity in the solubilized membrane fractions of cultured human keratinocytes and in the cytosolic fractions of cultured human fibroblasts. Maximum activity was induced by 1 alpha,25-dihydroxyvitamin D3 at 24 h. Sphingosine, which is believed to inhibit PKC mediated biological responses, blunted 1 alpha,25(OH)2D3's inducement of PKC activity in both keratinocytes and fibroblasts. Identical hormone treatment of vitamin D receptor deficient fibroblasts did not increase PKC activity. Treatment of keratinocytes and fibroblasts with 1 beta,25-dihydroxyvitamin D3, which is believed to be ineffective in inducing genomic responses, did not induce PKC activity.

A parathyroid hormone antagonist stimulates epidermal proliferation and hair growth in mice

The biologic action of parathyroid hormone (PTH)-related peptide (PTHrP) in normal skin was investigated in cultured human keratinocytes and in SKH-1 hairless mice. The results indicate that the PTHrP agonists human PTHrP-(1-34) and PTH(1-34) are potent inhibitors of epidermal cell proliferation. [Nle8,18,Tyr34]bovine PTH-(7-34)-amide, an antagonist of the PTH/PTHrP receptor, blocked the inhibitory effect of PTH-(1-34) in cultured keratinocytes. In the SKH-1 mice, PTH-(7-34) caused a 244% increase of [3H]thymidine incorporation into isolated epidermal DNA and 246% and 180% increases in the number and length of hair shafts, respectively. Thus, PTH and PTHrP may play an important role in the normal physiology of skin, and their agonists and antagonists have potentially wide therapeutic applications in the treatment of hyperproliferative skin disorders and aging skin and could also be effective in stimulating and maintaining hair growth.

The mRNA expression of the human 1,25-dihydroxyvitamin D3 receptor and the c-myc protooncogene in cultured human keratinocytes

The human vitamin D receptor mRNA expression in preconfluent human cultured keratinocytes was upregulated by treatment of these cells with 10(-8) M 1,25(OH)2D3 for 24 hours. Additionally, human c-myc mRNA expression was decreased in a dose dependent manner by 1,25(OH)2D3 in both preconfluent and confluent cultured human keratinocytes.