Geographic patterns of prostate cancer mortality. Evidence for a protective effect of ultraviolet radiation.

BACKGROUND. Prostate cancer is the most prevalent nonskin cancer among men in the United States and is the second leading cause of cancer deaths in men. The cause of prostate cancer remains obscure. Recently it was hypothesized that low levels of vitamin D, a hormone with potent antitumor properties, may increase the risk for clinical prostate cancer. METHODS. Because the major source of vitamin D is casual exposure to ultraviolet (UV) radiation, the authors examined the geographic distributions of UV radiation and prostate cancer mortality in 3073 counties of the contiguous United States using linear regression and trend surface analyses. RESULTS. The geographic distributions of UV radiation and prostate cancer mortality are correlated inversely (P < 0.0001). Prostate cancer mortality exhibits a significant north-south trend, with lower rates in the South. These geographic patterns are not readily explicable by other known risk factors for prostate cancer. CONCLUSIONS. These data lend support to the hypothesis that UV radiation may protect against clinical prostate cancer. Viewed in conjunction with other recent data, including those demonstrating a differentiating effect of vitamin D on human prostate cancer cells, these findings suggest that vitamin D may have an important role in the natural history of prostate cancer.     

Oral Rehabilitation of a Patient With Amelogenesis Imperfecta

A patient with Type I hypoplastic patterned amelogenesis imperfecta, subtype D, presented for prosthodontic evaluation. This article describes the developmental and pathophysiological background of this disease. A clinical report describing the diagnosis, treatment planning, and dental rehabilitation of the patient is reviewed.     

Vitamin E stimulates proliferation of experimental oral carcinoma cells in vitro

Vitamin E was found to have a stimulatory effect on the growth in culture of an epidermoid carcinoma cell line derived from chemically induced tumors of hamster buccal pouch. This effect was found to be dose related, with a maximum stimulatory effect at 10 microM. At a concentration of 100 microM, there was an inhibitory effect on both cell turnover and colony formation.     

Optimizing Suicide Gene Therapy for Head and Neck Cancer

An effective “suicide gene” therapy strategy in experimental studies has been the use of the herpes simplex virus thymidine kinase gene(HSV-tk) to sensitize tumors to the cytotoxic effects of ganciclovir administration. Previous studies using this model have focused on utilizing maximal viral titers and high levels of ganciclovir that are not compatible with human dosing. Because of the high ganciclovir doses and the maximal viral titers, this strategy has limited application to actual clinical scenarios. In the following studies the authors investigate tumor regression in an oral squamous cell carcinoma animal model as a function of variable adenoviral titers and more physiologic ganciclovir dosing. Using adenoviral titers ranging from 1 × 10⁸ to 2 × 10⁹ plaque forming units(pfu) to treat oral tumors, they found no statistical difference in tumor regression among the different viral doses, despite differences in mitotic activity. Each treatment group, however, demonstrated a significant effect on tumor regression when compared with controls. Furthermore, the authors were able to reduce the level of ganciclovir administration to 10 mg/kg twice daily from established levels of 100 to 150 mg/kg twice daily while maintaining significant tumor responses to the HSV-tk therapy. Mean survival of animals treated with this lower ganciclovir dose was significantly higher than in controls and was equal to established means based on previous studies using higher ganciclovir doses. The optimization of this suicide gene therapy strategy is imperative in order to minimize theoretical and known viral and ganciclovir toxicities while establishing a foundation upon which to design appropriate and effective clinical trials.     

Using the polymerase chain reaction to maintain DNA probe inventories in clinical and diagnostic laboratories

Clinical and diagnostic DNA laboratories must maintain a large inventory of DNA probes for use in hybridization studies. The preparation of plasmid DNA and isolation of DNA fragments for use as probes in both expensive and time consuming. We present here a rapid and relatively inexpensive method of producing large amounts of DNA fragments from stocks, using the polymerase chain reaction (PCR). Our experience over the past year using this technique has been very positive and we believe many laboratories could benefit by employing such a labor-saving approach to maintaining DNA probes. The technique uses the bacteriophage M13 DNA sequencing primers to amplify cloned inserts contained in commonly used plasmid vectors. As examples, we illustrate the use of DNA produced in this manner as probes for linkage analysis of the fragile X syndrome and for detection of deletions in the Duchenne muscular dystrophy gene. We have also found that at least two probes can be amplified in the same PCR reaction, allowing the detection of two different restriction fragment length polymorphisms (RFLP) simultaneously. It should be possible for laboratories to devise strategies particular to their individual needs using more than one DNA probe produced in the same PCR reaction to detect RFLP's. Such strategies would need only to consider that the predicted alleles of the multiple polymorphisms do not migrate to the same position during electrophoresis. Stocks of single or multiple probes produced by the PCR could then be maintained for more rapid Southern analyses.