Comparison of the expression of p53, p21, Bax and the induction of apoptosis between patients with basal cell carcinoma and normal controls in response to ultraviolet irradiation

AIM

Ultraviolet light (UV) is known to cause DNA damage in the epidermis. The damaged DNA is repaired or deleted by apoptosis to prevent the generation of cancer. It has been suggested that a deficient apoptotic mechanism may predispose individuals to skin cancer. Therefore, the response of normal controls and patients with basal cell carcinoma (BCC) to UV irradiation was investigated.

METHODS

The buttock skin from normal volunteers and patients with BCC was irradiated using solar simulated radiation (SSR). SSR mimics the effect of natural sunlight. Skin biopsies were excised and examined for p53, p21, and Bax protein expression and for the induction of apoptosis.

RESULTS

At 33 hours after UV irradiation, the induction of apoptosis was significantly higher (p = 0.04) in patients with BCC than in normal volunteers (Mann Whitney test). A trend towards higher p21 expression was found at 33 hours in patients with BCC (mean, 18.69 positive cells/field) than in normal volunteers (mean, 9.89), although this difference was not significant (p = 0.05 positive cells/field).

CONCLUSION

These results may imply that patients with BCC have enhanced sensitivity to UV irradiation or that there is some defect in the cell arrest or repair pathways, which results in damaged cells been pushed into apoptosis rather than repair.

Effects of black tea extract on transplantable and solid tumors in Swiss albino mice

The chemopreventive effects of green tea and its polyphenols are well documented in the literature. Epidemiological studies have suggested that green tea consumption might be effective in the prevention of certain human cancers. About 80% of the tea is consumed as black tea. Limited studies have been carried out to assess the usefulness of black tea as anti-carcinogen. The present set of investigations were initiated to study the anti-tumorigenic potential of aqueous black tea extract (ATE) in Swiss albino mice in in vivo animal bioassay, using 7, 12 dimethyl-benzanthracene (DMBA) as carcinogen. In the experimental group, 2% ATE was given orally as sole source of drinking water, while the control were allowed to drink normal water, ad lib. The results revealed that drinking of 2% ATE could effectively inhibit the onset of tumorigenesis, cumulative number of tumors and average number of tumors per mouse. In ATE drinking group 44% animals remained tumor free till the termination of experiment, i.e. 26 weeks. In the second set of experiment the preventive efficacy of 2% ATE of different cultivars of black tea, viz orthodox, CTC and dust were tested in Ehrlich Ascites (EA) tumor bearing mice. The preventive effects of ATE were observed in terms of increased life span (ILS). All the cultivars of tea showed more than 25% increase in life span of the animals. Cytotoxic effect of various doses of all three cultivars of black tea was also observed in vitro on EA cells.

Chemopreventive effects of black tea polyphenols in mouse skin model of carcinogenesis

In the present investigations, the antitumorigenic effect of black tea polyphenols (BTP) in two-stage mouse skin model of carcinogenesis was studied. The animals were initiated with a single "subcarcinogenic" topical dose (52 micrograms/200 microliters acetone) of 7, 12-dimethylbenzanthracene (DMBA). To evaluate the anti-tumour initiating activity, BTP was topically applied twice a week for three weeks prior to DMBA application, followed by topical treatment with 12-o-tetradecanoyl phorbol-13-acetate (TPA) (5 micrograms/200 microliters acetone, 2x/wk.) as promoter. For evaluation of antitumor promoting activity, BTP was applied prior to each treatment of TPA. BTP application showed marked inhibitory effect as antitumour initiator as well as antitumour promoter in mouse skin model of two-stage carcinogenesis. Since initiation involves genetic pathway and tumour promotion involves epigenetic pathway, it seems that BTP exerts its antitumorigenic effect by altering both genetic and epigenetic pathways.

Skin cancer chemopreventive effects of a flavonoid antioxidant silymarin are mediated via impairment of receptor tyrosine kinase signaling and perturbation in cell cycle progression

Enhanced tyrosine kinase activity due to aberrant or overexpression of receptor and/or non-receptor tyrosine kinases has been implicated in a variety of human malignancies including cutaneous neoplasms. Epidermal growth factor receptor (EGFR)-mediated tyrosine phosphorylation may be a primary indicator of signal transduction regulating cell growth and proliferation. Recent studies have shown that skin tumor promoters such as phorbol ester and ultraviolet B radiation activate EGFR in mouse skin as well as in cell culture. Similarly, oxidative stress, which is implicated in skin tumor promotion, also activates EGFR-mediated cell signaling. Since this signaling pathway has been suggested to be involved in skin tumor promotion, its impairment by antioxidants may lead to an efficient way for skin cancer prevention and therapy. Recently, we showed that silymarin, a flavonoid antioxidant, affords exceptionally high to complete protection against several skin tumor promoters caused tumor promotion in mouse skin. Employing human epidermoid carcinoma cells A431 that contain overexpressed EGFR, in this study, we assessed whether the anti-skin tumor promoting effects of silymarin are due to its inhibitory effect on EGFR activation and down stream signaling pathway leading to perturbations in cell cycle progression. Treatment of cells with silymarin resulted in a significant inhibition of ligand-induced activation of EGFR with no change in its protein levels. Silymarin treatment also resulted in a significant decrease in tyrosine phosphorylation of Shc, an immediate downstream target of EGFR, but no change in the protein levels of Shc. The inhibition of EGFR activation by silymarin was associated with a highly significant to complete inhibition of EGFR intrinsic kinase activity. Cells treated with silymarin also showed a significant G2-M arrest in cell cycle progression, and a highly significant inhibition of DNA synthesis and cell growth in a dose-dependent manner. Taken together, these results suggest that skin cancer chemopreventive effects of silymarin are mediated via impairment of EGFR signaling which ultimately leads to perturbation in cell cycle progression resulting in the inhibition of proliferation and induction of growth arrest.

Genetics of psoriasis: paternal inheritance and a locus on chromosome 6p

The pathogenesis of psoriasis is not fully understood, but population and twin studies suggest a large heritable component to the etiology. Several large population studies have also suggested a parental sex effect. Since 1994, three main genetic loci (on chromosomes 17q, 4q, and 6p) have been reported in genome scans. With a view to elucidating the genetic basis of psoriasis, we have carried out linkage analysis in a large number of families with well-characterized psoriasis. From a cohort of 1250 probands with psoriasis, 395 individuals (301 affected, 94 unaffected) in 103 families were recruited. Each subject was carefully examined by an experienced dermatologist and stringent diagnostic criteria applied. Genotypes were generated at 11 polymorphic loci on chromosomes 17q, 4q, and 6p and the results were analyzed parametrically and nonparametrically. In the population from which the probands were drawn, there was evidence of a parental sex effect, more probands having an affected father than an affected mother. Genetic anticipation was also apparent and most marked if the disease was inherited from the father. The loci on chromosomes 17 and 4 were not replicated but there was strong evidence for linkage to chromosome 6p (maximum two point LOD score 4.63 at D6S291). The evidence for linkage in sibling pair analysis was greatest when the allele was of paternal origin and was most significant in those families without psoriatic arthritis. These studies confirm the presence of a susceptibility gene on chromosome 6p. The available evidence suggests that a different genetic susceptibility may underlie psoriasis and psoriatic arthritis.

In vitro studies on the effect of linear alkyl benzene sulphonate on serum albumin

Synopsis Linear alkyl benzene sulphonate was found to influence the thermal and fluorescence profile of serum albumin in vitro, indicating the possibility of protein-detergent interaction in the skin irritancy of detergents.

Induction of epidermal NAD(P)H:quinone reductase by chemical carcinogens: a possible mechanism for the detoxification

NAD(P)H:quinone reductase, which plays an important role in the detoxification of carcinogenic metabolites as well as oxidative cellular damage, was found to be present in epidermal cytosol where its specific activity far exceeds (140-160%) the corresponding hepatic value. The effect of topical application of crude coal tar, 3-methylcholanthrene and polychlorinated biphenyl Aroclor 1254, on epidermal and hepatic cytosolic NAD(P)H:quinone reductase activities was investigated in neonatal rats, Sencar and athymic nude mice. A single topical application of each agent resulted in significant increases in epidermal (185%-389%) and hepatic (150-255%) enzyme activities. This inducible enzyme may play an important role in the detoxification of reactive quinone species during the course of malignant neoplasia and against oxidative cellular damage in skin.

Critical care problems in neonates. Colloid osmotic pressure in healthy and sick neonates

Clinical usefulness of colloid osmotic pressure (COP) measurements in adults has been well established. However, data in healthy and sick neonates are sparse. The present study established the COP changes in healthy term and preterm infants and in critically ill neonates. COP in healthy term (16.9 +/- 1.9 mm Hg) and preterm (15.4 +/- 1.3) infants was significantly lower than adults (21.6 +/- 3.6). Even in sick neonates, COP correlated with gestational age (n = 78, r = 0.63, p less than 0.001 , birth weight (r = 0.58, p less than 0.001) and total protein (n = 71, r = 0.58, p less than 0.001). Critically ill preterm infants with hyaline membrane disease had the lowest COP (11.5 +/- 1.2). Administration of 10% albumin failed to increase the COP significantly. In critically ill preterm infants who survived, the COP increased during the first postnatal week, whereas in nonsurvivors COP decreased significantly to less than 10 mm Hg.

Genetic and linkage analyses of dieldrin resistance in Anopheles culicifacies Giles

Genetic analysis indicates that dieldrin resistance in laboratory colonies of Anopheles culicifacies is under the control of codominant alleles of a locus in linkage group 3 (chromosome 3), approximately 31 map units from Acph (acid phosphatase).