CENP-50 is required for papilloma development in the two-stage skin carcinogenesis model.

CENP-50/U is a component of the CENP-O complex (CENP-O/P/Q/R/U) and localizes to the centromere throughout the cell cycle. Aberrant expression of CENP-50/U has been reported in many types of cancers. However, as Cenp-50/U-deficient mice die during early embryogenesis, its functions remain poorly understood in vivo. To investigate the role of Cenp-50/U in skin carcinogenesis, we generated Cenp-50/U conditional knockout (K14CreER -Cenp-50/Ufl/fl ) mice and subjected them to the 7,12-dimethylbenz(a)anthracene (DMBA)/terephthalic acid (TPA) chemical carcinogenesis protocol. As a result, early-stage papillomas decreased in Cenp-50/U-deficient mice. In contrast, Cenp-50/U-deficient mice demonstrated almost the same carcinoma incidence as control mice. Furthermore, mRNA expression analysis using DMBA/TPA-induced papillomas and carcinomas revealed that Cenp-50/U expression levels in papillomas were significantly higher than in carcinomas. These results suggest that Cenp-50/U functions mainly in early papilloma development and it has little effect on malignant conversion.

The parathyroid hormone regulates skin tumour susceptibility in mice.

Using a forward genetics approach to map loci in a mouse skin cancer model, we previously identified a genetic locus, Skin tumour modifier of MSM 1 (Stmm1) on chromosome 7, conferring strong tumour resistance. Sub-congenic mapping localized Parathyroid hormone (Pth) in Stmm1b. Here, we report that serum intact-PTH (iPTH) and a genetic polymorphism in Pth are important for skin tumour resistance. We identified higher iPTH levels in sera from cancer-resistant MSM/Ms mice compared with susceptible FVB/NJ mice. Therefore, we performed skin carcinogenesis experiments with MSM-BAC transgenic mice (Pth MSM-Tg) and Pth knockout heterozygous mice (Pth +/-). As a result, the higher amounts of iPTH in sera conferred stronger resistance to skin tumours. Furthermore, we found that the coding SNP (rs51104087, Val28Met) localizes in the mouse Pro-PTH encoding region, which is linked to processing efficacy and increased PTH secretion. Finally, we report that PTH increases intracellular calcium in keratinocytes and promotes their terminal differentiation. Taken together, our data suggest that Pth is one of the genes responsible for Stmm1, and serum iPTH could serve as a prevention marker of skin cancer and a target for new therapies.

CENP-R acts bilaterally as a tumor suppressor and as an oncogene in the two-stage skin carcinogenesis model.

CENP-R is a component of the CENP-O complex, including CENP-O, CENP-P, CENP-Q, CENP-R, and CENP-U and is constitutively localized to kinetochores throughout the cell cycle in vertebrates. CENP-R-deficient chicken DT40 cells are viable and show a very minor effect on mitosis. To investigate the functional roles of CENP-R in vivo, we generated CENP-R-deficient mice (Cenp-r-/- ). Mice heterozygous or homozygous for Cenp-r null mutation are viable and healthy, with no apparent defect in growth and morphology, indicating Cenp-r is not essential for normal development. Accordingly, to investigate the role of the Cenp-r gene in skin carcinogenesis, we subjected Cenp-r-/- mice to the 7,12-dimethylbenz(a)anthracene (DMBA)/TPA chemical carcinogenesis protocol and monitored tumor development. As a result, Cenp-r-/- mice initially developed significantly more papillomas than control wild-type mice. However, papillomas in Cenp-r-/- mice showed a decrease of proliferative cells and an increase of apoptotic cells. As a result, they did not grow bigger and some papillomas showed substantial regression. Furthermore, papillomas in Cenp-r-/- mice showed lower frequency of malignant conversion to squamous cell carcinomas. These results indicate Cenp-r functions bilaterally in cancer development: during early developmental stages, Cenp-r functions as a tumor suppressor, but during the expansion and progression of papillomas it functions as a tumor-promoting factor.

Studies on the interactions between drug and estrogen. II. On the inhibitory effect of 29 drugs reported to induce gynecomastia on the oxidation of estradiol at C-2 or C-17.

A study was investigated on the inhibitory effect of 29 drugs that have been reported to induce gynecomastia on the 2-hydroxylation of estradiol (E2) by recombinant P450 CYP3A4 and on the 17-oxidation of E2 by hepatic microsomal type II 17beta-hydroxysteroid dehydrogenase (17beta-HSD) of human male. The IC(50) values were determined for each drug relative to the 2-hydroxylation of E2 (catalytic activity: 1.54 nmol/nmol P450/min), and the inhibition constants (K(i)) were determined for 13 drugs of which IC(50) values were 100 microM or less. Ketoconazole exhibited the lowest inhibitory concentration, and IC(50) and K(i) values of 0.007 and 0.01 microM, respectively, were obtained. The IC(50) and K(i) values for each of the 12 remaining drugs were as follows: cyclosporin A (IC(50): 0.064, K(i): 0.30), nicardipine hydrochloride (0.55, 0.29), tacrolimus (0.64, 0.88), mandipine hydrochloride (3.9, 2.6), nisoldipine (10, 3.3), verapamil hydrochloride (10, 20), domperidone (13, 7.2), haloperidol (14, 55), nitrendipine (14, 2.5), chlormadinone acetate (16, 10), flutamide (30, 39) and omeprazole (49, 47). With the exception of cyclosporin A that exhibited a competitive inhibition, the inhibition mechanisms of these drugs were all non-competitive. Next, the percentage inhibition of the above 29 drugs relative to the 17-oxidation of E2 (catalytic activity: 0.47 nmol/mg protein/min) was investigated at the approximate therapeutic concentration (1 microM) and at the non-clinical overdose concentration (100 microM). Although none of the drugs investigated exhibited inhibitory effects at a concentration of 1 microM, spironolactone and ketoconazole at 100 microM demonstrated percentage inhibitions of 96% and 77%, respectively. When the K(i) values were determined for these two drugs, the former had a K(i) value of 2.4 microM and the latter, 41 microM, and both of their inhibition mechanisms were non-competitive. On the basis of the above results, a total of 14 drugs consisting of the above 13 drugs plus spironolactone were found to inhibit the 2-hydroxylation or 17-oxidation of E2 in the liver, and this is presumed to act as a trigger that causes as increase in the estradiol pool, followed by induction of gynecomastia.