**Acknowledgements**

VD3 and its analogs have been found to inhibit in vitro growth of primarily isolated fibroblasts and mast cells, but not Schwann cells. We also have found that growth of commercially available human epidermal melanocytes is efficiently inhibited by VD3 and its analogs. We used these human epidermal melanocytes in our study because it was difficult to obtain informed consent from patients to excise a large enough sample of a CALM to get the required number of melanocytes. Thus, whether the growth inhibition rate of primarily isolated melanocytes (NF1+/−) from NF1 patient CALMs is the same as that of the human epidermal

Given that we observed that the growth of Schwann cells was not affected by VD3 and its analogs, we extended our study further to whether an mTOR inhibitor (rapamycin) or Ras-MEK pathway inhibitor (lovastatin) could inhibit the growth of primary Schwann cells and fibroblasts isolated from NFs. It was found that these agents could inhibit growth of both Schwann cells and fibroblasts isolated from NFs. A combination of VD3 with rapamycin and/ or lovastatin did not increase the suppressive effects of either of these drugs on the growth of Schwann cells, but it did cause additive suppression of fibroblast growth. With regard to clinical use of VD3 or its analogs for NF1 patient skin lesions, our in vitro experimental results indicate a combination of rapamycin and/or lovastatin with VD3 should be more effective at suppressing NF growth in vivo. Although the tumorigenic cells in NFs are considered to be NF1−/− Schwann cells, supporting NF1+/− mast cells and/or fibroblasts are considered to be

We found definite inhibitory effects of 308-nm UVB irradiation (excimer light) on growth of all cells comprising the NF1 phenotype in vitro. We then studied whether NB-UVB irradiation brought about beneficial effects on skin lesions of patients with NF1. In addition, we measured changes in serum VD3 levels of these patients after long-term whole body NB-UVB irradiation. We observed that at least 6 months of irradiation significantly increased serum VD3 levels, which were accompanied by a lightening of generalized hyperpigmentation of the skin of most patients examined. Hyperpigmentation commonly resulting from UV or sun exposure, caused by induction of endothelin-1, was not detected with NB-UVB irradiation at doses of 0.2–

once weekly or biweekly, even if NB-UVB irradiation was continued for more than

Increases in NF1 patient serum VD3 levels by NB-UVB irradiation are in accord with a previous report suggesting NB-UVB irradiation for patients with either atopic dermatitis or psoriasis causes upregulation of serum 25-hydroxyvitamin D (calcidiol) [22]. Other reports suggest serum calcidiol levels in patients with NF1 are significantly lower than those of control subjects [23], and low levels of calcidiol have a negative correlation with severity of NF formation [24]. Also, reduced bone density and increased incidence of calcidiol deficiency in adults with NF1 have been reported [25]. Therefore, oral supply of VD3 and long-term NB-UVB irradiation could bring about benefits for both skin and internal lesions of NF1 patients; although, care should be taken to identify and minimize any adverse events caused by long-

To date, no evidence supports use of laser therapy for removal of CALMs. However, we experienced the virtual disappearance of a CALM on the nose of a young male patient with

melanocytes (NF1+/+) remains to be examined.

174 A Critical Evaluation of Vitamin D - Clinical Overview

essential for NF formation.

term NB-UVB irradiation.

0.5 J/cm2

3 years.

I thank Chiemi Sato and Tomoko Tsujita for their technical assistance.
