Browsing by Subject "cell proliferation"
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Item Akt Isoforms: A Family Affair in Breast Cancer(MDPI, 2021-07-09) Basu, Alakananda; Lambring, Christoffer B.Akt, also known as protein kinase B (PKB), belongs to the AGC family of protein kinases. It acts downstream of the phosphatidylinositol 3-kinase (PI3K) and regulates diverse cellular processes, including cell proliferation, cell survival, metabolism, tumor growth and metastasis. The PI3K/Akt signaling pathway is frequently deregulated in breast cancer and plays an important role in the development and progression of breast cancer. There are three closely related members in the Akt family, namely Akt1(PKBalpha), Akt2(PKBbeta) and Akt3(PKBgamma). Although Akt isoforms share similar structures, they exhibit redundant, distinct as well as opposite functions. While the Akt signaling pathway is an important target for cancer therapy, an understanding of the isoform-specific function of Akt is critical to effectively target this pathway. However, our perception regarding how Akt isoforms contribute to the genesis and progression of breast cancer changes as we gain new knowledge. The purpose of this review article is to analyze current literatures on distinct functions of Akt isoforms in breast cancer.Item Characterization of Protein Kinase C in Cisplatin Sensitive and Resistant Human Cervical Cancer HeLa Cells(2000-12-01) Mohanty, Sanghamitra; Basu, Alakananda; Simecka, Jerry; Dimitrijevich, DanMohanty, S., Characterization of protein kinase C in cisplatin sensitive and resistant human cervical cancer HeLa cells. Master of Science (Microbiology and Immunology), December, 2000. 37 pp., 11 illustrations, bibliography, 27 titles. Signal transduction plays a crucial role in carcinogenesis. A defect in signaling, by evading cell death or promoting cell proliferation, may result in neoplastic transformation or protection of cells from the cytotoxicity of anticancer drugs. Therefore, in order to understand the complex mechanism of drug resistance, it is relevant to probe into the important signal transduction pathways. Protein kinase C, a key signal transducer, influences cisplatin sensitivity in many cell lines. We examined whether or not the PKC signal transduction pathway is affected during development of resistance to cisplatin by tumor cells. PKC activators increased cisplatin sensitivity in both parental and cisplatin-resistant cells. Western blot analysis showed a slight decrease in cPKCα and nPKCε, an evaluation in nPKCδ and no change in the abundance of PKCϚ in HeLa/CP cells compared to HeLa cells. Though TPA-induced translocation of PKC isoforms was identical in both cell lines, down regulation of PKCδ was defective in resistant cells. Therefore, a deregulation in PKCδ was associated with cisplatin resistance.Item Characterization of the Role of PKN in TGF-Beta 1-Mediated Differentiation of Vascular Smooth Muscle Cells(2004-05-01) Deaton, Rebecca Ann; Dillon, Glenn; Shepard, Allan; Mallet, Robert T.Rebecca Ann Deaton, Characterization of the role of PKN in TGF-beta 1-mediated differentiation of vascular smooth muscle cells. Doctor of Philosophy (Biomedical Sciences), May 2004, 178 pp, 5 tables, 34 illustrations, references, 197 titles. Differentiated vascular smooth cells (SMCs) exhibit a work phenotype characterized by expression of several well-documented contractile apparatus-associated proteins. However, when exposed to mitogens such as serum or growth factors. SMCs retain the ability to de-differentiate into an “immature” proliferative phenotype, in which they lack contractile myofilaments. Proliferation of SMCs is involved in the formation of atherosclerotic plaques as well as arterial restenosis following balloon angioplasty. Thus, understanding the mechanism involved in maintain SMC differentiation process is critical to the development of therapies and treatments for the abnormal growth seen in these disease states. In this study, the molecular mechanisms through which transforming growth factor-beta 1 (TGF-B1) induces differentiation of SMCs were examined. The data presented demonstrate that TGF-B1 stimulates actin re-organization, up-regulation of SM-specific marker gene expression and inhibition of cell proliferation of PAC-1 SMCs. These characteristics are indicative of the differentiated phenotype. The effects of TGF-B1 can be blocked by pretreatment of the cells with either HA1077 or Y-27632, which inhibit the functions of the kinases downstream of RhoA. Moreover, TGF-B1 induced differentiation is correlated with an increase in the activity of RhoA and its downstream target, PKN. Over-expression of active PKN alone is sufficient to increase the transcriptional activity of the SM a-actin, SM-MHC and SM22 promoters in PAC-1 cells. In addition, the activity of SRF-GATA and MEF2, three transcription factors that are known to regulate expression of SM-specific marker genes, are also increased by PKN. Finally, examination of MAPK signaling cascades demonstrates that TGF-B1 increases the activity of MKK3/6 and p38 MAPK and decreases the activity of ERK1/2 and JNK ½. Co-expression of dominant negative p38 MAPK is sufficient to abolish PNK-mediated activation of SRF, GATA and MEF2 as well as PKN-mediated activation of SMC marker gene promoters. Taken together, these results identify components of an important intracellular signaling pathway through which TGF-B1 activates RhoA and PKN to promote differentiation of SMCs.Item Endothelin-1-Induced Signaling Involved in Extracellular Matrix Remodeling(2006-12-01) He, Shaoqing; Thomas Yorio; Neeraj Agarwal; Peter KoulenET-1-Induced Signaling in ECM Remodeling in Astrocytes. Shaoqing He, Department of Pharmacology & Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107. ET-1 levels are elevated under pathophysiological conditions, including glaucoma, however, ET-1’s ocular functions are not fully documented. Therefore, ET-1-induced signaling and ECM remodeling in astrocytes and at the optic nerve head were determined in this study. Three signaling pathways, including ERK1/2, PKC, and P13 kinase, were involved in ET-1-medicated cell proliferation of U373MG astrocytoma cells. Blocking one of these pathways completely abolished cell proliferation. It appeared that ERK1/2 activation was involved, but was independent of PKC and P13 kinase activation by ET-1. It was also determined that the ETB receptor was the dominant receptor involved in ERK1/2 phosphorylation and cell proliferation. In addition, ERK1/2 phosphorylation was not transactivated by the EGF receptor by ET-1. The studies also indicated that there was no activation of c/nPKC, although PKC was involved in cell proliferation. In U373MG astrocytoma cells, MAPK-ERK, PKC and P13K pathways appear to exert their roles in parallel without a direct, apparent “cross-talk”. Based on the signaling pathways obtained from U373MG astrocytoma cells, the regulation of MMPs/TIMPs and fibronectin in ET-1-activated human optic nerve head astroctyes (hONAs) was also determined. ET-1 not only induced rapid phosphorylation of ERK1/2 and PKC βI/ βII/δ but also increased the activity of MMP-2 and the expression of TIMP=1 and 2. The activity of MMP-2 was enhanced in the presence of inhibitors of MAPK or PKC in hONAs, whereas the expression of TIMP-1 and 2 was abolished. ET-1 increased the soluble fibronectin (FN) expression as well as FN matrix formation, however, the expression and deposition of FN were MAPK- and PKC-independent, whereas expression and activity of MMps and TIMPs were MAPK- and PKC-dependent. Therefore, ET-1 shifted the balance of MMPs/TIMPs and substrates that altered the ECM composition and subsequently let to ECM remodeling in activated hONA cells. ET-1’s effects on ECM remodeling at the optic nerve head were also examined following intravitreal administration of ET-1 in rats. The increased expression of MMP-9 and collagen VI was detected in both ETB deficient rats and wildtype Wistar rats post ET-1 intravitreal injection for 2 and 14 days, whereas the deposition of FN and collagen IV was unchanged. There was no significant difference in staining of MMP-9 and collagen VI between ETB deficient rats and wildtype Wistar rats. In this study, ECM remodeling was demonstrated in rats injected with ET-1 into the vitreous. Such changes in the ECM seen in the current study provide additional insight into the mechanisms that might explain the glaucomatous changes observed in ET-1-injection or perfusion models. In summary, ET-1 not only activated several signaling pathways in cell proliferation of astrocytes, but also modulated the expression of ECM molecules in vitro and in vivo, indicating that ET-1 plays a regulatory role in ECM remodeling. These effects coupled with observations that ET-1 levels are elevated in glaucoma patients, suggests that ET-1 may be involved in glaucomatous optic neuropathy.Item Regulation of Nucleo-Cytoplasmic Trafficking of Human Annexin II(2005-12-01) Liu, Jie; Jamboor K. Vishwanatha; Myoung Kim; Jerry SimeckaAnnexin II is a molecule having diversified functions in the cell. It contains a specific N terminus and a C terminal core domain that is homologous with other molecules in annexin family. To date, whether annexin II is a tumor promoter or suppressor is still a question of controversy. So the study of the functions of annexin II according to the specific cancer is of utmost importance for further manipulating this molecule to achieve the control of cancer. Nuclear export signal (NES) was found in the N terminus of annexin II, and nuclear localization of annexin II is cell cycle dependent. In addition, nuclear annexin II was shown to be phosphorylated. Based on these observations along with the previous finding that anexin II is a subunit of primer recognition proteins (PRP), it was proposed that nucleo-cytoplasmic trafficking of annexin II is a phosphorylation-regulated process which is relevant to cancer cell growth. Annexin II-null LNCaP cell line was used as a model to study the intracellular localization of annexin II without the effects of background endogenous annexin II. The stable clones expressing GFP alone, GFP fused wild type annexin II and GFP fused NES mutant annexin II were established. We observed that consistent nuclear localizing of NES mutant annexin II resulted in a decreased proliferation rate of LNCaP cells, while expression of wild type annexin II had no effect on the cell proliferation. However, the expression of wild type annexin II changed the morphology and decreased matrigel migration of LNCaP cells. These observations suggest that annexin II play a role in regulating cell proliferation, and re-expression of this molecule in annexin II-null cells can decrease the malignancy of the parental LNCaP cells. In order to investigate the effect phosphorylation on the subcellular localization of annexin II, we used site directed mutagenesis to convert the putative phosphorylation sites on the N terminus of annexin II to other amino acid to resemble the unphosphorylated/phosphorylated status of the residues. We found that double mutation of serine 11 and 25, which mimics the double phosphorylation of these residues, resulted in inhibition of nuclear entry of annexin II. So, there might be other phosphorylation sites responsible for the nuclear retention of annexin II. In highly malignant cancer cells, we found that annexin II is usually over-expressed and present in both the nucleus and the cytoplasm, i.e. although there is NES, annexin II can not be exported from the nucleus by CRM1 mediated pathway. Hela, DU-145 and PC-3 cell lines also have the same pattern of annexin II distribution. We confirmed this observation by using immunocytochemistry, Western blotting and immunoprecipitation. Using different antibody recognizing different domains of annexin II, we found that C terminus is masked in the nucleus. In order to know the relationship between the masking of C terminus and the nuclear retention of annexin II, truncation mutation was used to delete the C terminal core domain of annexin II. After we expressed the truncated annexin II in Hela, Du-145 and PC-3, we found that C terminal masking is not responsible for the nuclear retention of annexin II. So, we proposed that there are other nuclear factors interacting with the N terminus that prevent the binding of CRM1 and nuclear export of annexin II.Item The Enigmatic Protein Kinase C-eta(MDPI, 2019-02-13) Basu, AlakanandaProtein kinase C (PKC), a multi-gene family, plays critical roles in signal transduction and cell regulation. Protein kinase C-eta (PKCeta) is a unique member of the PKC family since its regulation is distinct from other PKC isozymes. PKCeta was shown to regulate cell proliferation, differentiation and cell death. It was also shown to contribute to chemoresistance in several cancers. PKCeta has been associated with several cancers, including renal cell carcinoma, glioblastoma, breast cancer, non-small cell lung cancer, and acute myeloid leukemia. However, mice lacking PKCeta were more susceptible to tumor formation in a two-stage carcinogenesis model, and it is downregulated in hepatocellular carcinoma. Thus, the role of PKCeta in cancer remains controversial. The purpose of this review article is to discuss how PKCeta regulates various cellular processes that may contribute to its contrasting roles in cancer.