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Biomedical subjects

K V Patel

Publications and source records attributed to K V Patel.

16 recordsLinked to original sources
PubMed2000

The relationship between human papillomavirus and p53 gene in conjunctival squamous cell carcinoma.

PURPOSE: The p53 tumor-suppressor gene has been documented to exist in mutated forms in many types of squamous cell carcinoma in the body. Also in conjunctival squamous cell carcinoma, human papillomavirus (HPV) is accepted as an oncogenic factor. The objective of our study was to establish a correlation between p53 overexpression and the presence of HPV infection within tumor tissues from patients with conjunctival squamous cell carcinoma. METHODS: Tissue sections obtained from paraffin-embedded conjunctival squamous cell carcinoma specimens from 23 patients were examined with light microscopy, polymerase chain reaction (PCR), and immunohistochemistry. RESULTS: Seventy-eight percent of tumors were positive for p53, whereas 22% were positive for HPV. The proportion of patients positive for both p53 and HPV was 17%, whereas another 17% of the patients were negative for both p53 and HPV. Therefore no significant disproportion was found in the distribution of patients' HPV status and p53 status (p = 1.00). No significant correlation or linear association was found between the HPV status and p53 status (r = 0.022; p = 0.920). CONCLUSION: We could not show any statistical association between abnormal p53 gene-product expression by immunohistochemistry in conjunctival squamous cell carcinomas and HPV infection by PCR detection techniques.

Antibodies, Neoplasm↗
PubMed1997

Stimulation or endothelin-1 secretion by human breast cancer cells through protein kinase A activation: a possible novel paracrine loop involving breast fibroblast-derived prostaglandin E2.

Breast cancer cells secrete endothelin-1 (ET-1), which may act as a paracrine mitogen in breast tumours. The paracrine factors and signal transduction pathways responsible for regulating ET-1 production in breast cancer are unknown. In this study we have examined the involvement of the protein kinase A (PKA) signalling pathway in the control of ET-1 secretion in the human breast cancer cell line MCF-7. Treatment of MCF-7 cells with various agents that activate protein kinase A (PKA) through increases in intracellular cAMP levels including forskolin, cholera toxin (ChT), the cAMP analogue 8-Br-cAMP, or the cAMP phosphodiesterase inhibitor, 3-isobutyl-1-methyl-xanthine (IBMX) all markedly increased ET-1 release. Prostaglandin E2 (PGE2) while stimulating cAMP production, but not inositol lipid hydrolysis also significantly stimulated ET-1 release. Activation of PKC by 2-O-tetradecanoyl phorbol 13-acetate (TPA) also stimulated ET-1 secretion in MCF-7 cells. The PKA inhibitor H-89 attenuated the ET-1 response to PGE2, forskolin and ChT, but not that due to the PKC agonist TPA. The possibility that human breast fibroblasts (HBFs) are a target for ET-1 action with regard to PGE2 production was also investigated, and revealed that while HBFs were unresponsive to ET-1 alone, pretreatment with the cytokine IL-beta greatly potentiated PGE2 release in response to ET-1. In conclusion our results show that activation of either the PKA or PKC signalling pathways in human breast cancer cells increases ET-1 secretion. We also found that HBFs release PGE2 after treatment with ET-1 and that PGE2 itself stimulates ET-1 production in MCF-7 cells. The implication of this potential novel paracrine loop may be significant in view of the high levels of PGE2 and ET-1 found in malignant breast tissues.

Breast Neoplasms↗
PubMed1995

Prostaglandin E2 production and metabolism in human breast cancer cells and breast fibroblasts. Regulation by inflammatory mediators.

Malignant human breast tumours contain high levels of prostaglandin E2 (PGE2). However, the mechanisms controlling PGE2 production in breast cancer are unknown. This in vitro study investigates the capacity for PGE2 synthesis and metabolism in several human breast cancer cell lines and early passage human breast fibroblasts and seeks to identify potential regulatory factors which may control these pathways. Basal PGE2 production rose up to 30-fold in breast fibroblast lines on addition of exogenous arachidonic acid (10 microM), whereas no such changes were observed in six out of seven cancer cell lines, with the exception of modest increases in MDA-MB-231 cells. Interleukin 1 beta (IL-1 beta) also induced PGE2 production in breast fibroblasts in the presence of excess substrate, consistent with cyclo-oxygenase induction by the cytokine. Under these conditions only Hs578T cells and MDA-MB-231 cells demonstrated large increases in PGE2 in response to IL-1 beta or phorbol ester; no such responses were seen in MCF-7, T47-D, ZR-75-1, BT-20 or CLF-90-1 cells. In the absence of added arachidonate, bradykinin (BK) and endothelin-1 (ET-1), potentiated PGE2 production in IL-1 beta-treated fibroblasts, possibly by mobilising endogenous substrate. PGE2 also stimulated ET-1 production by breast cancer cells. In co-cultures with T47-D cells both basal and stimulated PGE2 production by breast fibroblasts was greatly reduced. This appeared to be due to metabolic inactivation by the cancer cell since T47-D cells readily converted PGE2 to 15-keto-PGE2. This apparent 15-hydroxy-PG dehydrogenase activity was stimulated by TPA and inhibited by cycloheximide. In conclusion, breast fibroblasts, particularly under the influence of inflammatory mediators, provide a potentially rich source for PGE2 production in breast tumours, whereas significant contributions from the epithelial tumour component may be restricted to cancer cells exhibiting an invasive phenotype. Metabolic inactivation by the cancer cells may also play an important role in the regulation of breast tumour PGE2 levels.

Arachidonic Acid↗
PubMed1995

Human breast cancer cells contain a phosphoramidon-sensitive metalloproteinase which can process exogenous big endothelin-1 to endothelin-1: a proposed mitogen for human breast fibroblasts.

Endothelin-1 (ET-1) levels are elevated in human breast tumours compared with normal and benign tissues, and in the presence of insulin-like growth factor 1 (IGF-I) ET-1 is a potent mitogen for human breast fibroblasts. In this study we have examined the ability of intact human breast cancer cell lines to process exogenously added big ET-1 (1-38) to the active mature ET-1 peptide by using a specific radioimmunometric assay. In both hormome-dependent (MCF-7, T47-D) and hormone-independent (MDA-MB-231) breast cancer cell lines the putative endothelin-converting enzyme (ECE) exhibited apparent Michaelis-Menten kinetics when converting added big ET-1 to ET-1. Both basal ET-1 production and exogenously added big ET-1 to ET-1 conversion were greatly reduced in all three cell lines in response to the metalloproteinase inhibitor phosphoramidon but were insensitive to other classes of protease inhibitors. Inhibition was also observed when cells were incubated in the presence of the divalent cation chelators 1,10-phenanthroline and EDTA. In MCF-7 cells the optimal pH for the ECE activity using a saponin cell permeabilisation procedure was found to residue within a narrow range of 6.2-7.26. Our results indicate that human breast cancer cells contain a neutral phosphoramidon-sensitive metalloproteinase which can process big ET-1 to ET-1. In the breast this conversion could contribute substantially to the local extracellular levels of this proposed paracrine breast fibroblast mitogen.

Aspartic Acid Endopeptidases↗
PubMed1992

Heterologous regulation of inositol lipid hydrolysis in human breast cancer cells by oestradiol 17 beta, bombesin and fluoroaluminate.

Inositol lipid turnover has been implicated in the action of oestradiol 17 beta and bombesin-related peptides on the human breast cancer cell line MCF-7. In the present study, in addition to measuring inositol lipid turnover as indicated by inositol monophosphate (IP) accumulation, we have also monitored the effect of oestradiol on the incorporation of both 3H-inositol and 14C-glycerol into MCF-7 cell phospholipids. Pre-treatment of MCF-7 cells with oestradiol (10 nM) for 48 hr stimulated a 4.3-fold increase in IP production. This was similarly accompanied by a 3.4-fold increase in the incorporation of 3H-inositol into total phosphoinositides and a 40% increase in cell growth. The oestrogen antagonist LYI 17018 completely attenuated these effects. Oestradiol also stimulated 14C-glycerol incorporation into phosphatidyl inositol, -choline and -ethanolamine by 97%, 82% and 99%, respectively. IP production in response to bombesin was potentiated by oestradiol in a dose-dependent fashion. Fluoroaluminate (AlF4-) stimulated a dose-dependent increase in IP production and oestradiol pre-treatment increased the sensitivity of this IP response to AlF4-. Medroxyprogesterone acetate inhibited bombesin-stimulated IP production but had no effect on the response to AlF4-. Our data suggest that the oestrogenic action on basal IP production in MCF-7 cells may reflect an effect on inositol lipid synthesis rather than turnover. However, the potentiation by oestradiol of both bombesin- and AlF4(-)-stimulated inositol lipid hydrolysis suggests the operation of a post-receptor regulatory mechanism(s) which is independent of the inositol lipid pool size.

Aluminum↗
PubMed1992

Bombesin and glucocorticoids stimulate human breast cancer cells to produce endothelin, a paracrine mitogen for breast stromal cells.

Human breast cancer cells have been recently reported to produce endothelin (ET) 1. To investigate the potential regulation of ET production in breast cancer cells, we have measured the release of ET-like immunoreactivity from the T47D cell line in response to various paracrine/endocrine factors. Bombesin (0.1 microM) and cortisol (1 microM) stimulated maximal respective increases in IR-ET release to 580 and 369% of basal values after 6 h. The responses to cortisol and bombesin were additive. The response to bombesin was dose dependent with a median effective dose around 1 nM and was inhibited by the receptor antagonist [Leu13-psi-CH2NH-Leu14]bombesin. Pretreatment of T47D cells with pertussis toxin had no effect on bombesin-induced inositol lipid hydrolysis but inhibited ET-like immunoreactivity release in response to bombesin in the presence of glucocorticoid, by 56%. ET-1 (10 nM) and insulin-like growth factor (10 ng/ml) stimulated modest separate increases in DNA synthesis in human breast fibroblasts of 35 and 71%, respectively, but together exhibited a strong synergistic response to 905% of control values. This in vitro study demonstrates the potential for bombesin and glucocorticoid to regulate ET production in human breast cancer cells, which may in turn have a paracrine influence on neighboring stromal cell function.

Bombesin↗
PubMed1992

Inhibition of DNA synthesis and growth in human breast stromal cells by bradykinin: evidence for independent roles of B1 and B2 receptors in the respective control of cell growth and phospholipid hydrolysis.

The paracrine and intracellular mechanisms controlling stromal cell growth in the normal or neoplastic breast are unknown. This in vitro study uses human breast fibroblasts to investigate a potential role for the inflammatory peptide mediator bradykinin (BK) in the regulation of DNA synthesis and signal transduction in these cells. Bradykinin stimulated a dose-dependent increase in inositol lipid hydrolysis and cytosolic Ca2+ levels in serum-starved fibroblasts derived from both normal and breast tumor tissue. Bradykinin also caused a dose-dependent decrease in cell growth and [3H]thymidine incorporation into DNA in breast fibroblasts. Epidermal growth factor (EGF) and insulin-like growth factor 1 both stimulated DNA synthesis in breast fibroblasts. Bradykinin inhibited this mitogenic effect of EGF but not that due to insulin-like growth factor 1. The binding of 125I-labeled EGF to fibroblasts was also inhibited by BK. Prostaglandin E2 also inhibited fibroblast DNA synthesis, and the cyclooxygenase inhibitor indomethacin partially reversed the inhibitory action of BK on DNA synthesis. Studies with BK receptor antagonists and agonists indicate that inositol lipid signalling and arachidonic acid mobilization in response to BK are B2 receptor-mediated pathways, whereas the inhibition of DNA synthesis appears to be via B1 receptors. Although these data support a role for prostaglandins and EGF receptor down-modulation in the inhibitory action of BK on DNA synthesis in breast fibroblasts, a B1 receptor-mediated pathway is also implicated. This study highlights a potential pathophysiological role for BK as a negative regulator of breast stromal cell growth.

Arachidonic Acid↗
PubMed1992

Evidence for a role for protein kinase C in the modulation of bombesin-activated cellular signalling in human breast cancer cells.

The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) is a potent activator of protein kinase C (PKC) and is known to affect a variety of biochemical processes in human breast cancer cells. In the present study we have employed MCF-7 cells to investigate the effects of TPA on inositol lipid signalling, the putative pathway leading to PKC activation and intracellular Ca2+ mobilization. Phosphoinositide hydrolysis in MCF-7 cells was stimulated by bombesin (BN) as evidenced by increases in both inositol phosphate production and cytidine diphosphate diacylglycerol (CDP-DG) accumulation. Pretreatment of MCF-7 cells with TPA caused attenuation of both these BN-induced responses. This inhibitory action of TPA on inositol phosphate production was mimicked by diacylglycerol analogues and was reversed by staurosporine, H-7 and tamoxifen, all known inhibitors of PKC. Furthermore, putative down-regulation of PKC by prolonged TPA pretreatment also reversed the inhibitory action of TPA and enhanced BN-induced phosphoinositide hydrolysis. TPA also inhibited BN-induced increases in cytosolic Ca2+ concentration ([Ca2+]i) and caused a dose-dependent inhibition of epidermal growth factor (EGF) binding in MCF-7 cells. However, EGF receptor occupancy was unaffected by BN. These data support an inhibitory role for PKC in the regulation of phosphoinositide hydrolysis and [Ca2+]i in breast cancer cells and provide a potential mechanism for feedback regulation of this signalling pathway in these cells.

Bombesin↗
PubMed1991

Modulation of inositol lipid hydrolysis in human breast cancer cells by two classes of bombesin antagonist.

Inositol lipid hydrolysis was monitored in the human breast cancer cell line MCF-7 in response to various bombesin (BN) and substance P (SP) analogues. Both members of the BN family of peptides, i.e. BN and gastrin-releasing peptide (GRP), stimulated a dose-related increase in total inositol phosphate production, with a similar half-maximal effective dose (ED50) around 1 nM. The BN receptor antagonist [Leu13-psi-CH2NH-Leu14]-BN (LLBN) at 1 microM was devoid of agonist activity and displaced the BN dose-response to the right, resulting in a tenfold increase in the ED50 for BN. BN also stimulated a dose-related increase in 45Ca2+ efflux which was also inhibited by LLBN. Two SP analogues [DArg1,D-Pro2,D-Trp7,9,Leu11]-SP and [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-SP ([APheTL]-SP), both antagonized BN-stimulated inositol lipid hydrolysis. [APheTL]-SP (60 and 80 microM) alone also exhibited considerable agonist activity which was not antagonized by LLBN. Indeed, a sub-threshold dose of [APheTL]-SP (40 microM) in the presence of LLBN (10 microM) potentiated the inositol lipid hydrolysis response. BN, GRP, LLBN and [APheTL]-SP all inhibited binding of 125I-labelled GRP to MCF-7 cells, to 50% of that occurring in the absence of the peptides, at concentrations of 150 pM, 150 pM, 150 nM and 600 nM respectively. These data are consistent with the presence of separate but interacting receptors or binding sites for BN and SP analogues, which are coupled to a common signal transduction pathway in human breast cancer cells.

Binding Sites↗
PubMed1990

Mitogenic peptides in breast cyst fluid: relationship with intracystic electrolyte ratios.

Women with palpable breast cysts which are lined with apocrine epithelium may be at higher risk of developing breast cancer than women with breast cysts which are lined with flattened epithelium, the former group being characterized by intracystic sodium to potassium ratios below 3, while the latter group has intracystic sodium to potassium ratios above 3. In this study the distribution of intracystic concentrations of the mitogenic peptides, epidermal growth factor, endothelin and gastrin-releasing peptide in the 2 groups of breast cysts were compared to see whether differences in concentrations between the 2 cyst groups might provide an explanation for the higher risk of breast cancer observed in women with "apocrine" breast cysts. The concentrations of epidermal growth factor and gastrin-releasing peptide were significantly higher in the low electrolyte ratio group (p less than 0.001). There was no difference in endothelin concentrations between the 2 groups. Negative correlations were found between epidermal growth factor concentrations and Na+/K+ and between gastrin-releasing peptide concentrations and Na+/K+ (p less than 0.001). A positive correlation was found between gastrin-releasing peptide and epidermal growth factor concentrations in breast cyst fluid (p less than 0.001). The significantly higher intracystic concentrations of both epidermal growth factor and gastrin-releasing peptide in the low-electrolyte-ratio group may provide an explanation for the higher risk of breast cancer which has been observed in women with "apocrine" breast cysts.

Endothelins↗
PubMed1990

Activation of inositol phospholipid signaling and Ca2+ efflux in human breast cancer cells by bombesin.

Members of the bombesin-related family of peptides (BRPs) are mitogenic for a variety of cell types; however, a role for these peptides has not been previously described in human breast cancer. Early membrane receptor signal transduction mechanisms associated with bombesin action include phospholipase C-mediated inositol phospholipid hydrolysis and the elevation of cytosolic Ca2+ levels. We have investigated a potential role for BRPs in breast cancer by studying their effect on phospholipid hydrolysis, 45Ca2+ efflux, and cell growth in the human breast cancer cell line MCF-7. Bombesin stimulated a dose-dependent increase in the hydrolysis product inositol monophosphate during 1 h with a half-maximal effect around 1 nM. A transient increase in inositol trisphosphate in response to bombesin was also apparent at 2 min. Two distinct bombesin receptor antagonists inhibited this bombesin-induced phospholipid hydrolysis. Both bombesin- and gastrin-releasing peptide also stimulated a dose-related increase in inositol phosphate production in T47D cells, a different human breast cancer cell line. The efflux of 45Ca2+ from prelabeled MCF-7 cells was also stimulated by bombesin. This apparent cellular Ca2+ mobilization was partly dependent on extracellular Ca2+ and was inhibited by Ni2+. Despite this activation of putative mitogenic signaling pathways, bombesin had no effect on either proliferation or DNA synthesis in MCF-7 cells. These data implicate a functional role for BRPs in human breast cancer.

Bombesin↗
PubMed1990

Abnormal osteocalcin binding in rheumatoid arthritis.

Studies of osteocalcin in the serum and synovial fluid of patients with rheumatoid arthritis (RA) and osteoarthritis (OA) showed the presence of significant amounts of osteocalcin in synovial fluid and that the values in RA synovial fluid were significantly lower than in OA synovial fluid. In addition, the osteocalcin in OA synovial fluid bound almost completely to hydroxyapatite, whereas a significant proportion of the osteocalcin in RA synovial fluid did not. These studies suggest that patients with severe RA produce low amounts of active osteocalcin and higher than expected amounts of inactive osteocalcin in the synovial fluid. They provide some evidence that osteoblast function may be abnormal in the osteoporosis of RA.

Arthritis, Rheumatoid↗
PubMed1987

Vitamin A and D status of black South African women and their babies.

Knowledge of the vitamin D status of pregnant and lactating women in developing countries is very limited. An elective visit to the Transkei therefore provided us with the opportunity to study the relationship between the vitamin A and D status of dark-skinned mothers and babies resident in an environment of high sunshine exposure. 25-hydroxyvitamin D, retinol and retinol binding protein (RBP) were measured in serum samples collected from 43 black South African women and their babies, shortly after delivery. The results were compared with values obtained on sera from pregnant white and black women resident in the UK. The values for serum retinol in the Transkei mothers and babies were low. This accords with the poor nutrition and consequent high childhood mortality observed in this population. In contrast, the serum 25-OHD values were normal. This suggests that in these malnourished black South African mothers, normal vitamin D status is maintained by actinic synthesis.

Adult↗
PubMedDate not supplied

Studies in release behavior of diltiazem HCl from matrix tablets containing (hydroxypropyl)methyl cellulose and xanthan gum.

(Hydroxypropyl)methyl cellulose and xanthan gum were used as hydrophilic matrixing agents for preparing modified release tablets of diltiazem HCl. The amount of (Hydroxypropyl)methyl cellulose and xanthan gum exhibited significant effect on drug release from the tablets prepared by direct compression technique. Xanthan gum showed a higher ability to retard the drug release than (Hydroxypropyl)methyl cellulose. A 2(2) + 1 factorial design was adopted to study the effect of amount of (Hydroxypropyl)methyl cellulose and xanthan gum on percent drug released in first hour (Y60) and the time required for 90% drug dissolution (t90). A response surface plot is generated for investigating the effect of the independent variables on t90. The tablets containing 90 mg diltiazem HCl, 45 mg (Hydroxypropyl)methyl cellulose and 45 mg xanthan gum showed drug release upto 12 h. The value of similarity factor, f2, for the selected batch was found to be 85.1 when the dissolution study was carried out in water or simulated gastric fluid, indicating pH independent drug dissolution. The selected batch also showed a comparable release profile with a market product (f2 = 60.2). Linear relationship was observed between percent drug released and degree of swelling. The kinetics of the drug release fitted well to the Hixson-Crowell equation. It can be concluded that by using a suitable blend of (Hydroxypropyl)methyl cellulose and xanthan gum desired modified drug release can be achieved.

Antihypertensive Agents↗