Biomedical subjects

Sanjay Katiyar

Publications and source records attributed to Sanjay Katiyar.

8 recordsLinked to original sources

PubMed2006

Somatic excision demonstrates that c-Jun induces cellular migration and invasion through induction of stem cell factor.

Cancer cells arise through sequential acquisition of mutations in tumor suppressors and oncogenes. c-Jun, a critical component of the AP-1 complex, is frequently overexpressed in diverse tumor types and has been implicated in promoting cellular proliferation, migration, and angiogenesis. Functional analysis of candidate genetic targets using germ line deletion in murine models can be compromised through compensatory mechanisms. As germ line deletion of c-jun induces embryonic lethality, somatic deletion of the c-jun gene was conducted using floxed c-jun (c-jun(f/f)) conditional knockout mice. c-jun-deleted cells showed increased cellular adhesion, stress fiber formation, and reduced cellular migration. The reduced migratory velocity and migratory directionality was rescued by either c-Jun reintroduction or addition of secreted factors from wild-type cells. An unbiased analysis of cytokines and growth factors, differentially expressed and showing loss of secretion upon c-jun deletion, identified stem cell factor (SCF) as a c-Jun target gene. Immunoneutralizing antibody to SCF reduced migration of wild-type cells. SCF addition rescued the defect in cellular adhesion, cellular velocity, directional migration, transwell migration, and cellular invasion of c-jun(-/-) cells. c-Jun induced SCF protein, mRNA, and promoter activity. Induction of the SCF promoter required the c-Jun DNA-binding domain. c-Jun bound to the SCF promoter in chromatin immunoprecipitation assays. Mutation of the c-Jun binding site abolished c-Jun-mediated induction of the SCF promoter. These studies demonstrate an essential role of c-Jun in cellular migration through induction of SCF.

Animals↗

PubMed2006

Cyclin D1 induction of cellular migration requires p27(KIP1).

The cyclin D1 gene is amplified and overexpressed in human breast cancer, functioning as a collaborative oncogene. As the regulatory subunit of a holoenzyme phosphorylating Rb, cyclin D1 promotes cell cycle progression and a noncatalytic function has been described to sequester the cyclin-dependent kinase inhibitor protein p27. Cyclin D1 overexpression correlates with tumor metastasis and cyclin D1-deficient fibroblasts are defective in migration. The genetic mechanism by which cyclin D1 promotes migration and movement is poorly understood. Herein, cyclin D1 promoted cellular migration and cytokinesis of mammary epithelial cells. Cyclin D1 enhanced cellular migratory velocity. The induction of migration by cyclin D1 was abolished by mutation of K112 or deletion of NH(2)-terminal residues 46 to 90. These mutations of cyclin D1 abrogated physical interaction with p27(KIP1). Cyclin D1(-/-) cells were p27(KIP1) deficient and the defect in migration was rescued by p27(KIP1) reintroduction. Conversely, the cyclin D1 rescue of cyclin D1(-/-) cellular migration was reversed by p27(KIP1) small interfering RNA. Cyclin D1 regulated p27(KIP1) abundance at the posttranslational level, inhibiting the Skp2 promoter, Skp2 abundance, and induced p27(KIP1) phosphorylation at Ser(10). Together, these studies show cyclin D1 promotes mammary epithelial cell migration. p27(KIP1) is required for cyclin D1-mediated cellular migration.

Actins↗

PubMed2006

p27Kip1 repression of ErbB2-induced mammary tumor growth in transgenic mice involves Skp2 and Wnt/beta-catenin signaling.

Expression of the cyclin-dependent kinase (Cdk) inhibitor (p27(Kip1)) is frequently reduced in human tumors, often correlating with poor prognosis. p27(Kip1) functions as a haploinsufficient tumor suppressor; however, the mechanism by which one allele of p27(Kip1) regulates oncogenic signaling in vivo is not well understood. We therefore investigated the mechanisms by which p27(Kip1) inhibits mammary tumor onset. Using the common background strain of FVB, p27(Kip1) heterozygosity (p27(+/-)) accelerated ErbB2-induced mammary tumorigenesis. We conducted microarray analyses of mammary tumors developing in mice with genetic haploinsufficiency for p27(Kip1) expressing a mammary-targeted ErbB2 oncogene. Global gene expression profiling and Western blot analysis of ErbB2/p27(+/-) tumors showed that the loss of p27(Kip1) induced genes promoting lymphangiogenesis, cellular proliferation, and collaborative oncogenic signaling (Wnt/beta-catenin/Tcf, Cdc25a, Smad7, and Skp2). Skp2 expression was induced by ErbB2 and repressed by p27(Kip1). Degradation of p27(Kip1) involves an SCF-type E3 ubiquitin ligase, including Skp2. The Skp2 component of the SCF(SKP2) complex that degrades p27(Kip1) was increased in ErbB2 tumors correlating with earlier tumor onset. In both murine and human ErbB2-overexpressing breast cancers, p27(Kip1) levels correlated inversely with Skp2. p27(Kip1) haploinsufficiency activated Wnt/beta-catenin/hedgehog signaling. Reintroduction of p27(Kip1) inhibited beta-catenin induction of Tcf-responsive genes (Siamosis, c-Myc, and Smad7). p27(Kip1) is haploinsufficient for ErbB2 mammary tumor suppression in vivo and functions to repress collaborative oncogenic signals including Skp2 and Wnt/beta-catenin signaling.

Animals↗

PubMed2006

Cyclin D1 repression of nuclear respiratory factor 1 integrates nuclear DNA synthesis and mitochondrial function.

Cyclin D1 promotes nuclear DNA synthesis through phosphorylation and inactivation of the pRb tumor suppressor. Herein, cyclin D1 deficiency increased mitochondrial size and activity that was rescued by cyclin D1 in a Cdk-dependent manner. Nuclear respiratory factor 1 (NRF-1), which induces nuclear-encoded mitochondrial genes, was repressed in expression and activity by cyclin D1. Cyclin D1-dependent kinase phosphorylates NRF-1 at S47. Cyclin D1 abundance thus coordinates nuclear DNA synthesis and mitochondrial function.

Amino Acid Sequence↗

PubMed2006

Cyclin D1 determines mitochondrial function in vivo.

The cyclin D1 gene encodes a regulatory subunit of the holoenzyme that phosphorylates and inactivates the pRb tumor suppressor to promote nuclear DNA synthesis. cyclin D1 is overexpressed in human breast cancers and is sufficient for the development of murine mammary tumors. Herein, cyclin D1 is shown to perform a novel function, inhibiting mitochondrial function and size. Mitochondrial activity was enhanced by genetic deletion or antisense or small interfering RNA to cyclin D1. Global gene expression profiling and functional analysis of mammary epithelial cell-targeted cyclin D1 antisense transgenics demonstrated that cyclin D1 inhibits mitochondrial activity and aerobic glycolysis in vivo. Reciprocal regulation of these genes was observed in cyclin D1-induced mammary tumors. Cyclin D1 thus integrates nuclear DNA synthesis and mitochondrial function.

Animals↗

PubMed2005

p53 gene mutation and human papillomavirus (HPV) infection in esophageal carcinoma from three different endemic geographic regions of India.

Infection of high-risk human papillomaviruses (HPVs), particularly the HPV types 16 and 18 and mutation or aberrant expression of the p53 tumour suppressor gene, has strongly been implicated in human esophageal carcinoma, which shows a great variation in geographic distribution. Neither the reason(s) for such a variation nor the etiopathogenesis of the disease is clearly understood. The present study has been carried out to determine prevalence of high-risk HPV types 16 and 18 and the p53 gene mutation in patients from three distinctly different endemic geographic regions of India, viz. Kashmir, Dibrugarh, and New Delhi where esophageal cancer is most prevalent. The people from each of these regions differ considerably in their food, drinking, smoking and chewing habits (tobacco and betel nut) and ethnic background. While PCR was employed to detect high-risk HPV types 16 and 18 DNA sequences, PCR-SSCP and direct nucleotide sequencing was used for analysis of p53 mutation. Out of a total of 101 biopsy specimens of carcinoma esophagus analysed, the frequency of HPV was found to be the highest 14/32 (44%) in Dibrugarh followed by 33% (11/33) in Kashmir, but, interestingly, no high-risk HPV could be detected in New Delhi patients who showed the highest frequency (30.6%) of p53 mutation as against only 12.5% in Dibrugarh and 6.1% in Kashmir. The difference in the frequency of p53 mutation between the three regions was statistically highly significant (0.018). Out of a total of 21 nucleotide alterations observed, 12 missense, five frameshift and four were silent changes. The p53 exon 7 appears to be the 'hot-spot' for esophageal cancer as it alone was responsible for more than 76% (13/17) of mutations and more than 95% (20/21) of the patients with p53 mutation were smokers. The results demonstrate differential distribution of HPV infection and p53 mutation in esophageal cancer from different geographic regions of India and this could be due to variation in diet, drinking, and tobacco habit, including ethnic, socio-cultural and genetic variation.

Adult↗

PubMed2003

Polymorphism of the p53 codon 72 Arg/Pro and the risk of HPV type 16/18-associated cervical and oral cancer in India.

Infection of high risk human papillomaviruses (HPVs) specifically the types 16 and 18 has been strongly implicated in the development of cervical cancer. The E6 oncoproteins of these high risk HPVs are known to bind and induce degradation of p53 tumour suppressor protein through the ubiquitin pathways. This degradation is controlled by a common polymorphism of the p53 gene encoding either a proline or an arginine at its codon 72 in exon 4. Recently, it has been demonstrated that the presence of homozygous arginine at codon 72 renders p53 about seven times more susceptible to E6-mediated proteolytic degradation as well as to cervical cancer than those with proline homozygotes or proline/arginine heterozygotes. In India, prevalence of HPV as well as cancers of the uterine cervix and the oral cavity are highest in the world. We have examined this allele-specific predisposition in cervical and oral cancer which is associated with HPV as well as in a non-HPV-linked cancer of the breast. We have carried out investigation in women comprising whole spectrum of cervical lesions with 128 HPV 16/18 positive and 35 HPV negative invasive cervical carcinomas and 34 cases of HPV (16/18) positive and 16 HPV negative cervical dysplasias (mild, moderate and severe) and 104 age-group-matched healthy women as controls. Additionally, we have analysed p53Arg-Pro polymorphism in 13 high risk HPV positive and 31 HPV negative oral cancers along with 20 normal controls and 77 breast cancers with 41 age-matched healthy controls. We observed more than two fold higher risk for homozygous arginine (chi2 = 6.3, df = 2, p = 0.04; OR = 2.3; 95% CI: 1.08-5.16) for HPV 16/18-positive cervical carcinomas when comparison was made only between HPV positive cervical cancers and normal controls but most interestingly, no significant association either in the frequency of homozygous arginine or proline alleles or their heterozygotes could be observed when all the three groups i.e. HPV-positive, HPV-negative cervical cancers and controls were considered simultaneously. No difference was also observed for either arginine or proline polymorphism between women with precancerous lesions of the uterine cervix carrying HPV 16/18 infection and controls. Similarly, increased risk of oral or breast cancer could not be correlated with the polymorphism of arginine/proline allele. Thus the interaction between HPV oncoproteins and the p53 gene polymorphism specifically, homozygous arginine at codon 72 appears to play no role in the development of either cervical or oral cancer and also it can not serve as a biomarker for early identification of cervical, oral or breast cancer.

Adult↗

PubMed2002

Toremifene prevents prostate cancer in the transgenic adenocarcinoma of mouse prostate model.

The chemopreventive efficacy of toremifene, an antiestrogen, was evaluated in the transgenic adenocarcinoma of mouse prostate (TRAMP) model. TRAMP mice were segregated into three groups: (a) the low-dose toremifene group (6.6 mg/kg/day); (b) the high-dose toremifene group (33 mg/kg/day); and (c) the control placebo group. Efficacy of treatment was measured by the absence of palpable tumor. To extend these studies using more sensitive techniques, TRAMP mice were then treated with placebo, flutamide (an antiandrogen; 33 mg/kg/day), or toremifene (10 mg/kg/day). Animals from each treatment group were sacrificed at 7, 10, 15, 20, 25, and 30 weeks of age, and prostate tissues and seminal vesicles were harvested. Tissues from animals (n = 5) in each group were evaluated by wholemount dissections of genitourinary tracts, histology, immunohistochemistry, and Western blot analyses. Blood was pooled per group to measure estradiol and testosterone hormonal levels. Tumors formed at week 17 in the placebo group (n = 10), at week 21 in the high-dose toremifene group (n = 12), and at week 29 in the low-dose toremifene group (n = 12). This represents an increased tumor latency of up to 12 weeks. By 33 weeks, all animals in the placebo group had tumors compared with only 35% of the animals treated with toremifene. Although both flutamide and toremifene decreased tumor incidence compared with the placebo, toremifene was more effective than flutamide. High-grade prostatic intraepithelial neoplasia was observed in animals in the placebo group, but not in animals treated with toremifene. Moreover, toremifene-treated animals had prolonged survival compared with placebo-treated animals. By 33 weeks of age, 100% of the placebo-treated animals had developed palpable tumors and died, whereas 60% of the toremifene-treated animals were tumor free. T antigen levels in the prostate of toremifene-treated animals were similar to those of placebo-treated, age-matched animals. Whereas serum estradiol levels remained unchanged, the total and free testosterone levels were elevated in the toremifene-treated group. Toremifene treatment did not affect androgen receptor levels. Because toremifene prevented prostate cancer in a milieu of elevated blood free testosterone levels with no change in prostate androgen receptor expression, the mechanism of toremifene's chemopreventive activity may be through nonandrogenic pathways, such as estrogen receptor signaling.

Adenocarcinoma↗