To glean insights into the mechanism of their action, we assessed the effects of two flavonoids, ... more To glean insights into the mechanism of their action, we assessed the effects of two flavonoids, quercetin (Qu) and luteolin (Lu), on the growth and epidermal growth factor receptor (EGFR) tyrosine kinase activity of MiaPaCa-2 cancer cells. Exposure of these EGFR-expressing cells to 20 microM Qu or Lu resulted in concomitant decreases in cellular protein phosphorylation and growth. On the cellular level, Qu and Lu sensitivity correlated with EGFR levels and rapid cell proliferation, indicating the possibility of targeting those cells most prone to neoplastic progression. Cell treatment with the flavonoids markedly diminished the extent of cellular protein phosphorylation, by effectively modulating protein tyrosine kinase (PTK) activities, including that of EGFR. Immunocomplex kinase assay revealed that both Qu and Lu inhibited the PTK activities responsible for the autophosphorylation of EGFR as well as for the transphosphorylation of enolase. Treatment of the cells with Qu or Lu also reduced the phosphotyrosyl levels of 170-, 125-, 110-, 65-, 60-, 44-, 30- and 25-kDa proteins. We identified the 170-kDa phosphotyrosylprotein as EGFR. Qu and Lu exhibited a specific action in hampering the levels of phosphorylation of this and the aforementioned proteins, while having no discernible effect on their synthesis. A time-dependent attenuation of the phosphorylation of the above proteins was demonstrable. Treatment of the cells with Qu or Lu for 6 hours showed little inhibition, but prolonging the cell treatment for 24 hours caused the suppression of phosphorylation. Further continuation of the cell treatment culminated in the induction of apoptosis, characteristically exhibiting shrinkage of the cell morphology, DNA fragmentation and poly(ADP-ribose)polymerase (PARP) degradation. The onset of apoptosis and associated events occurred in a time-dependent fashion. The data clearly demonstrate that MiaPaCa-2 cells respond to Qu and Lu by a parallel reduction in cellular protein phosphorylation and cellular proliferation. The flavonoid-evoked attenuation of the phosphorylation of EFGR and of other proteins appeared to be transient, since removal of the flavonoid from the cell growth medium after 24 hours of incubation followed by exposure to 10 nm EGF, restored protein phosphorylation and cellular proliferation. Such an addition of EGF was also able to reverse Qu- or Lu-induced cell growth inhibition and diminish nuclear digestion evoked by 20 microM Qu or Lu. Both Qu and Lu were able to reverse the effect of EGF biochemically as well as functionally. Based on the evidence accrued, the above proteins could be implicated in growth signal transduction and the subtle changes in their phosphorylation, as effected by flavonoids, utilized as a reliable guide to predict growth response. The antiproliferative effect of flavonoids might result, at least in part, from the modulation of the EGF-mediated signaling pathway. The results indicate that the blockade of the EGFR-signaling pathway by the PTK inhibitors Qu and Lu significantly inhibits the growth of MiaPaCa-2 cells and induces apoptosis. The modulation of EGFR kinase appears to be a critically important, intrinsic component of Qu- and Lu-induced growth suppression, even though other mechanisms could also have contributed to the net effect.
The purpose of the present research was to determine the physiological roles of endogenous relaxi... more The purpose of the present research was to determine the physiological roles of endogenous relaxin in pregnant rats by passive immunization with a monoclonal antibody specific for rat relaxin (MCA1). Recently, Lao Guico-Lamm and Sherwood demonstrated that rats treated with MCA1 throughout the second half of pregnancy exhibited prolonged delivery and reduced pup survival at birth compared to controls.I first examined the hypothesis that the influence of endogenous relaxin on birth is attributable, at least partly, to its effects on the cervix. The initial study showed that cervices obtained on day 22 of pregnancy from rats treated with MCA1 throughout the second half of pregnancy were markedly smaller and less extensible than cervices from controls. The second study demonstrated that rats treated with MCA1 during only the last three days of pregnancy, the so-called antepartum period, exhibited prolonged delivery and reduced cervical growth and softening compared to controls. However, passive immunization of relaxin during the antepartum period has less profound effects on cervical growth and softening and litter delivery than did passive immunization of relaxin throughout the second half of pregnancy. Collectively, studies 1 and 2 provided strong support for the hypothesis that relaxin enables rapid and safe delivery of the pups, at least partly, by promoting growth and softening of the cervix.The second study also demonstrated that pups born of relaxin deficient rats exhibited reduced weight and postpartum survival rate. Accordingly, I examined the hypothesis that endogenous relaxin contributes to the development of the mammary apparatus and lactational performance. On day 22 rats treated with MCA1 throughout the second half of pregnancy exhibited smaller nipples and abnormal morphology of the mammary glands compared to controls. Furthermore, MCA1-treated rats, cesarean sectioned near term, showed poor lactational performance towards foster pups born of untreated intact rats as judged by pup growth and survival.In conclusion, the present research establishes two vital physiological needs for endogenous relaxin during pregnancy. Relaxin promotes not only the cervical growth and softening required for birth but also the development of the mammary apparatus essential for growth and survival of the young during lactation.U of I OnlyETDs are only available to UIUC Users without author permissio
Role of C1GALT1 in the phosphorylation of RTKs and downstream effectors mediated by galectin-4, E... more Role of C1GALT1 in the phosphorylation of RTKs and downstream effectors mediated by galectin-4, EGF, and heregulin.
Functional signaling by differential genes in 22Rv1-M3 versus 22Rv1 cells analyzed using a bioinf... more Functional signaling by differential genes in 22Rv1-M3 versus 22Rv1 cells analyzed using a bioinformatic approach and transcriptional analysis.
Galectin-4 expression regulates the induction of EMT-related genes and cell invasion in 22Rv1-M3 ... more Galectin-4 expression regulates the induction of EMT-related genes and cell invasion in 22Rv1-M3 cells.
Role of C1GALT1 in the phosphorylation of RTKs and downstream effectors mediated by galectin-4, E... more Role of C1GALT1 in the phosphorylation of RTKs and downstream effectors mediated by galectin-4, EGF, and heregulin.
Galectin-4 expression regulates the induction of EMT-related genes and cell invasion in 22Rv1-M3 ... more Galectin-4 expression regulates the induction of EMT-related genes and cell invasion in 22Rv1-M3 cells.
Functional signaling by differential genes in 22Rv1-M3 versus 22Rv1 cells analyzed using a bioinf... more Functional signaling by differential genes in 22Rv1-M3 versus 22Rv1 cells analyzed using a bioinformatic approach and transcriptional analysis.
To glean insights into the mechanism of their action, we assessed the effects of two flavonoids, ... more To glean insights into the mechanism of their action, we assessed the effects of two flavonoids, quercetin (Qu) and luteolin (Lu), on the growth and epidermal growth factor receptor (EGFR) tyrosine kinase activity of MiaPaCa-2 cancer cells. Exposure of these EGFR-expressing cells to 20 microM Qu or Lu resulted in concomitant decreases in cellular protein phosphorylation and growth. On the cellular level, Qu and Lu sensitivity correlated with EGFR levels and rapid cell proliferation, indicating the possibility of targeting those cells most prone to neoplastic progression. Cell treatment with the flavonoids markedly diminished the extent of cellular protein phosphorylation, by effectively modulating protein tyrosine kinase (PTK) activities, including that of EGFR. Immunocomplex kinase assay revealed that both Qu and Lu inhibited the PTK activities responsible for the autophosphorylation of EGFR as well as for the transphosphorylation of enolase. Treatment of the cells with Qu or Lu also reduced the phosphotyrosyl levels of 170-, 125-, 110-, 65-, 60-, 44-, 30- and 25-kDa proteins. We identified the 170-kDa phosphotyrosylprotein as EGFR. Qu and Lu exhibited a specific action in hampering the levels of phosphorylation of this and the aforementioned proteins, while having no discernible effect on their synthesis. A time-dependent attenuation of the phosphorylation of the above proteins was demonstrable. Treatment of the cells with Qu or Lu for 6 hours showed little inhibition, but prolonging the cell treatment for 24 hours caused the suppression of phosphorylation. Further continuation of the cell treatment culminated in the induction of apoptosis, characteristically exhibiting shrinkage of the cell morphology, DNA fragmentation and poly(ADP-ribose)polymerase (PARP) degradation. The onset of apoptosis and associated events occurred in a time-dependent fashion. The data clearly demonstrate that MiaPaCa-2 cells respond to Qu and Lu by a parallel reduction in cellular protein phosphorylation and cellular proliferation. The flavonoid-evoked attenuation of the phosphorylation of EFGR and of other proteins appeared to be transient, since removal of the flavonoid from the cell growth medium after 24 hours of incubation followed by exposure to 10 nm EGF, restored protein phosphorylation and cellular proliferation. Such an addition of EGF was also able to reverse Qu- or Lu-induced cell growth inhibition and diminish nuclear digestion evoked by 20 microM Qu or Lu. Both Qu and Lu were able to reverse the effect of EGF biochemically as well as functionally. Based on the evidence accrued, the above proteins could be implicated in growth signal transduction and the subtle changes in their phosphorylation, as effected by flavonoids, utilized as a reliable guide to predict growth response. The antiproliferative effect of flavonoids might result, at least in part, from the modulation of the EGF-mediated signaling pathway. The results indicate that the blockade of the EGFR-signaling pathway by the PTK inhibitors Qu and Lu significantly inhibits the growth of MiaPaCa-2 cells and induces apoptosis. The modulation of EGFR kinase appears to be a critically important, intrinsic component of Qu- and Lu-induced growth suppression, even though other mechanisms could also have contributed to the net effect.
The purpose of the present research was to determine the physiological roles of endogenous relaxi... more The purpose of the present research was to determine the physiological roles of endogenous relaxin in pregnant rats by passive immunization with a monoclonal antibody specific for rat relaxin (MCA1). Recently, Lao Guico-Lamm and Sherwood demonstrated that rats treated with MCA1 throughout the second half of pregnancy exhibited prolonged delivery and reduced pup survival at birth compared to controls.I first examined the hypothesis that the influence of endogenous relaxin on birth is attributable, at least partly, to its effects on the cervix. The initial study showed that cervices obtained on day 22 of pregnancy from rats treated with MCA1 throughout the second half of pregnancy were markedly smaller and less extensible than cervices from controls. The second study demonstrated that rats treated with MCA1 during only the last three days of pregnancy, the so-called antepartum period, exhibited prolonged delivery and reduced cervical growth and softening compared to controls. However, passive immunization of relaxin during the antepartum period has less profound effects on cervical growth and softening and litter delivery than did passive immunization of relaxin throughout the second half of pregnancy. Collectively, studies 1 and 2 provided strong support for the hypothesis that relaxin enables rapid and safe delivery of the pups, at least partly, by promoting growth and softening of the cervix.The second study also demonstrated that pups born of relaxin deficient rats exhibited reduced weight and postpartum survival rate. Accordingly, I examined the hypothesis that endogenous relaxin contributes to the development of the mammary apparatus and lactational performance. On day 22 rats treated with MCA1 throughout the second half of pregnancy exhibited smaller nipples and abnormal morphology of the mammary glands compared to controls. Furthermore, MCA1-treated rats, cesarean sectioned near term, showed poor lactational performance towards foster pups born of untreated intact rats as judged by pup growth and survival.In conclusion, the present research establishes two vital physiological needs for endogenous relaxin during pregnancy. Relaxin promotes not only the cervical growth and softening required for birth but also the development of the mammary apparatus essential for growth and survival of the young during lactation.U of I OnlyETDs are only available to UIUC Users without author permissio
Role of C1GALT1 in the phosphorylation of RTKs and downstream effectors mediated by galectin-4, E... more Role of C1GALT1 in the phosphorylation of RTKs and downstream effectors mediated by galectin-4, EGF, and heregulin.
Functional signaling by differential genes in 22Rv1-M3 versus 22Rv1 cells analyzed using a bioinf... more Functional signaling by differential genes in 22Rv1-M3 versus 22Rv1 cells analyzed using a bioinformatic approach and transcriptional analysis.
Galectin-4 expression regulates the induction of EMT-related genes and cell invasion in 22Rv1-M3 ... more Galectin-4 expression regulates the induction of EMT-related genes and cell invasion in 22Rv1-M3 cells.
Role of C1GALT1 in the phosphorylation of RTKs and downstream effectors mediated by galectin-4, E... more Role of C1GALT1 in the phosphorylation of RTKs and downstream effectors mediated by galectin-4, EGF, and heregulin.
Galectin-4 expression regulates the induction of EMT-related genes and cell invasion in 22Rv1-M3 ... more Galectin-4 expression regulates the induction of EMT-related genes and cell invasion in 22Rv1-M3 cells.
Functional signaling by differential genes in 22Rv1-M3 versus 22Rv1 cells analyzed using a bioinf... more Functional signaling by differential genes in 22Rv1-M3 versus 22Rv1 cells analyzed using a bioinformatic approach and transcriptional analysis.
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Papers by Jiuan-Jiuan Hwang