Helicobacter hepaticus is a new bacterial species that is homologous to Helicobacter pylori, a hu... more Helicobacter hepaticus is a new bacterial species that is homologous to Helicobacter pylori, a human gastric carcinogen. H. hepaticus causes chronic active hepatitis, with progression to hepatocellular tumors. We hypothesized that chronic up-regulation of epidermal growth factor (EGF), transforming growth factor-alpha, and nuclear oncogenes (cyclin D1 and c-Myc), all known to transform by overexpression, might contribute to tumorigenesis. Livers from mice that were 6-18 months old were analyzed, including nonneoplastic and preneoplastic tissues and tumors, along with age-matched controls, by immunohistochemistry and immunoblotting. EGF and transforming growth factor-alpha were increased at the earliest stage, with a further increase in EGF in tumors. Cyclin D1, cyclin-dependent kinase 4, and c-Myc were strongly increased in all infected livers, with even greater increases in tumors. An increase in cyclin D1/cyclin-dependent kinase 4 complex was also demonstrated in tumors, and its functionality was confirmed by an increase in the hyperphosphorylated:hypophosphorylated retinoblastoma protein ratio. Our findings suggest a possible cooperation of growth factors, cell cycle proteins, and transcription factors during the development of H. hepaticus-associated liver tumors and may have relevance to human cancers associated with bacterial, viral, or parasitic infections.
Growth factors bind to membrane receptor tyrosine kinases, resulting in autophosphorylation and s... more Growth factors bind to membrane receptor tyrosine kinases, resulting in autophosphorylation and subsequent binding to proteins with SH2 domains, including growth factor receptor-bound protein 2 (Grb2). Grb2 bridges receptors to tyrosine kinase substrates such as SHC and SOS, which in turn facilitate the activation of downstream signaling pathways, including Ras and mitogen-activated protein kinase (MAPK). Overexpression of Grb2 has been demonstrated in several types of neoplasia but has not been investigated in liver tumorigenesis. Here we investigated Grb2 expression in liver lesions in N-nitrosodimethylamine (NDMA)-treated Helicobacter hepaticus-infected and -noninfected A/J mice at 1 year of age. Previously, we reported (6) that infection promotes the development of these NDMA-initiated tumors. In controls, Grb2 immunostaining was absent from normal hepatic tissues, whereas the inflammatory lesions in infected livers were positive for cytoplasmic Grb2 in both hepatocytes and infi...
Cytotoxic, Mutagenic and Carcinogenic Potential of Heavy Metals Related to Human Environment, 1997
Human exposure to metals, environmentally or occupationally, continues to increase in many areas ... more Human exposure to metals, environmentally or occupationally, continues to increase in many areas [1]. Such exposures of both men and women may adversely affect their reproductive capability, and impact on fertility and on pregnancy outcomes. Recent reviews are available, covering studies of effects on fertility, spontaneous abortions, premature delivery, low birth weight, and teratogenesis in humans [2, 3], and developmental toxicity in laboratory animals [4]. An even more insidious concern is the possibility of causation of persistent subtle deleterious effects in the offspring, as a result of preconception, transplacental, or neonatal exposure. Neurological effects have been documented, especially for transplacental and neonatal exposure to lead [5] and methylmercury [6]. In addition, over the last several years, evidence has been accumulating from both epidemiological and experimental investigations that perinatal exposure to metals may result in a later increase in risk for cancer. This evidence is reviewed here.
A new murine Helicobacter species, Helicobacter hepaticus, infects the livers of mice, causing a ... more A new murine Helicobacter species, Helicobacter hepaticus, infects the livers of mice, causing a progressive chronic active hepatitis culminating in hepatocellular tumors. To examine the role of chronic H. hepaticus infection in carcinogenesis, H. hepaticus-infected male infant mice of A/JCr strain were given a single ip dose of N-nitrosodimethylamine (NDMA). Noninfected A/J mice similarly treated with NDMA served as controls. The effect of hepatitis induced by H. hepaticus was studied for 64 wk. At 31-36 wk, the incidence of hepatocellular adenomas in infected mice was significantly higher than in noninfected mice (82 vs 52%; p = 0.05). The multiplicity of hepatocellular tumors was also significantly higher in infected mice compared to noninfected mice (3.2 ± 0.09 vs 0.09 ± 0.2; p = 0.03). At 51-64 wk, many (10/18) infected mice developed hepatocellular carcinomas while only 2 of 19 control mice developed such tumors ( p = 0.005). Overexpression of cyclin D was observed in hepatocy...
We are writing in response to comments that you have received from Drs Maioli and Fortino to our ... more We are writing in response to comments that you have received from Drs Maioli and Fortino to our recent manuscript published in the Breast Cancer Research and Treatment [1]. We are encouraged that our data describing the role of PKCd, MAPK/ERK, and p27 in anti-proliferative activity effects of inositol hexaphosphate (IP6) in breast cancer cells are in agreement with Drs Maioli and Fortino’s theory on PKCd role in cellular processes. We agree with their proposed model by which PKCd upon physiological activation inhibits ERK activity through direct phosphorylation and blockage of Raf-1, resulting in accumulation of p27. The authors further suggest that in the case of a strong pharmacological activation and/or forced expression of PKCd, the associated molecular events involve phosphorylation of ERK through effectors other than Raf-1, resulting in p27 degradation and p21 induction. Most of the literature reports are consistent with the PKCd having an anti-proliferative and a tumor suppressing activity in different cellular models. However, due to a several findings indicating the pro-proliferative and possibly co-oncogenic role of PKCd [2], it is rather difficult to reconcile its role in proliferation and survival. A recent comprehensive review by Jackson and Foster [3] indicates that PKCd regulates several molecular players involved in cellular processes. The most important partners to PKCd are molecules in Ras/Raf/MEK/ ERK pathway [4], which, when activated, have been shown to contribute to cellular proliferation and oncogenesis. Therefore, it appears that the status of some of the molecules in this pathway will determine whether activation of PKCd will lead to proliferation or to cell cycle arrest. Activated PKCd might cause indirect activation of ERK, and this could be an important component of its ability to positively regulate cellular proliferation [4,5]. What it is not clear is why and under which circumstances PKCd activates ERK. Jackson and Foster summarized that PKCd can contribute to ERK activation at several points in the Ras/Raf/MEK/ERK signaling pathway: (1) upstream of Ras, (2) downstream of Ras but upstream of Raf, and down-stream of Raf but upstream of MEK [3]. Our results on investigation of molecular mechanism of IP6 anti-proliferative effects in human breast cancer cell lines with different molecular background (MCF-7 and MDA-MB 231) clearly indicate that IP6 activity involves the activation and membrane translocation of PKCd (Figure 1) [1]. This presents a very interesting experimental model through which the interaction of PKCd and its partnering kinases could be investigated. In MCF-7 cells (estrogen receptor-positive, wild type Ras and p53) activation of PKCd by IP6 led to downregulation of ERK after 30 min of treatment [1]. However, in MDA-MB 231 cells (estrogen receptornegative, mutated K-Ras and p53) the activation of PKCd activity by IP6 treatment at the same dose caused an increase of activity of ERK1/ERK2, which was sustained from 2 min through 24 h. There was no change in the expression of total ERK1/ERK2 (Figure 2). In
Inositol hexaphosphate (IP6) is a naturally occurring polyphosphorylated carbohydrate with demons... more Inositol hexaphosphate (IP6) is a naturally occurring polyphosphorylated carbohydrate with demonstrated anti-proliferative and anti-cancer activity in mammary cells. We hypothesized that IP6 modulates cell cycle proteins by action on cytoplasmic signaling molecules. The effects of both pharmacological (2 mM) and physiological (100 microM) doses of IP6 on major PKC isoforms (PKCalpha, delta, epsilon, beta and zeta), PI3-K/Akt and ras/Erk1/2 were evaluated. Treatment of MCF-7 human breast cancer cells with 2 mM IP6 for 24 h caused a 3.1-fold increase in the expression of anti-proliferative PKCdelta. Similar results were observed with 100 microM IP6 at only 30-60 min post-treatment. IP6 also caused an increase in PKCdelta activity, shown by its translocation from cytosol to membrane. No changes in expression of PKC alpha, delta, epsilon, beta and zeta were detected. Additionally, IP6 caused a decrease of Erk1/2 and Akt activity. Among cell cycle control proteins, IP6 resulted in increased p27Kip1 protein levels and marked reduction of pRb phosphorylation. Specificity of the IP6 effects on p27Kip1 and pRb in MCF-7 cells (hormone-dependent) were additionally confirmed in highly invasive hormone-independent MDA-MB 231 breast cancer cells. Use of specific pharmaclogical inhibitors of PKC delta, MEK/Erk, and PI3K/Akt pathways indicated that the IP6-mediated effects on PKC delta were responsible for up-regulation of p27Kip, and pRb hypo-phosphorylation. In addition, IP6-induced apoptosis detected in MCF-7 cells appeared also to be PKC delta-dependent. Our data suggest potential usefulness of IP6 as a novel therapeutic modulator of PKC delta and p27Kip1, an important prognostic factor in human breast cancers.
We review the hepatocarcinogenic effects of fungal cultures of Fusarium verticillioides ( = Fusar... more We review the hepatocarcinogenic effects of fungal cultures of Fusarium verticillioides ( = Fusarium moniliforme) strain MRC 826 in male BD IX rats. Subsequent chemical analyses of the fumonisin B (FB) mycotoxin content in the culture material used and long-term carcinogenesis studies with purified FB 1 provide information about dose–response effects, relevance of hepatotoxicity during FB 1-induced carcinogenesis, and the existence of a no-effect threshold. Fumonisin intake levels of between 0.08 and 0.16 mg FB/100 g body weight (bw)/day over approximately 2 years produce liver cancer in male BD IX rats. Exposure levels < 0.08 mg FB/100 g bw/day fail to induce cancer, although mild toxic and preneoplastic lesions are induced. The nutritional status of the diets used in the long-term experiments was marginally deficient in lipotropes and vitamins and could have played an important modulating role in fumonisin-induced hepatocarcinogenesis. Short-term studies in a cancer initiation/...
Helicobacter hepaticus is a new bacterial species that is homologous to Helicobacter pylori, a hu... more Helicobacter hepaticus is a new bacterial species that is homologous to Helicobacter pylori, a human gastric carcinogen. H. hepaticus causes chronic active hepatitis, with progression to hepatocellular tumors. We hypothesized that chronic up-regulation of epidermal growth factor (EGF), transforming growth factor-alpha, and nuclear oncogenes (cyclin D1 and c-Myc), all known to transform by overexpression, might contribute to tumorigenesis. Livers from mice that were 6-18 months old were analyzed, including nonneoplastic and preneoplastic tissues and tumors, along with age-matched controls, by immunohistochemistry and immunoblotting. EGF and transforming growth factor-alpha were increased at the earliest stage, with a further increase in EGF in tumors. Cyclin D1, cyclin-dependent kinase 4, and c-Myc were strongly increased in all infected livers, with even greater increases in tumors. An increase in cyclin D1/cyclin-dependent kinase 4 complex was also demonstrated in tumors, and its functionality was confirmed by an increase in the hyperphosphorylated:hypophosphorylated retinoblastoma protein ratio. Our findings suggest a possible cooperation of growth factors, cell cycle proteins, and transcription factors during the development of H. hepaticus-associated liver tumors and may have relevance to human cancers associated with bacterial, viral, or parasitic infections.
Growth factors bind to membrane receptor tyrosine kinases, resulting in autophosphorylation and s... more Growth factors bind to membrane receptor tyrosine kinases, resulting in autophosphorylation and subsequent binding to proteins with SH2 domains, including growth factor receptor-bound protein 2 (Grb2). Grb2 bridges receptors to tyrosine kinase substrates such as SHC and SOS, which in turn facilitate the activation of downstream signaling pathways, including Ras and mitogen-activated protein kinase (MAPK). Overexpression of Grb2 has been demonstrated in several types of neoplasia but has not been investigated in liver tumorigenesis. Here we investigated Grb2 expression in liver lesions in N-nitrosodimethylamine (NDMA)-treated Helicobacter hepaticus-infected and -noninfected A/J mice at 1 year of age. Previously, we reported (6) that infection promotes the development of these NDMA-initiated tumors. In controls, Grb2 immunostaining was absent from normal hepatic tissues, whereas the inflammatory lesions in infected livers were positive for cytoplasmic Grb2 in both hepatocytes and infi...
Cytotoxic, Mutagenic and Carcinogenic Potential of Heavy Metals Related to Human Environment, 1997
Human exposure to metals, environmentally or occupationally, continues to increase in many areas ... more Human exposure to metals, environmentally or occupationally, continues to increase in many areas [1]. Such exposures of both men and women may adversely affect their reproductive capability, and impact on fertility and on pregnancy outcomes. Recent reviews are available, covering studies of effects on fertility, spontaneous abortions, premature delivery, low birth weight, and teratogenesis in humans [2, 3], and developmental toxicity in laboratory animals [4]. An even more insidious concern is the possibility of causation of persistent subtle deleterious effects in the offspring, as a result of preconception, transplacental, or neonatal exposure. Neurological effects have been documented, especially for transplacental and neonatal exposure to lead [5] and methylmercury [6]. In addition, over the last several years, evidence has been accumulating from both epidemiological and experimental investigations that perinatal exposure to metals may result in a later increase in risk for cancer. This evidence is reviewed here.
A new murine Helicobacter species, Helicobacter hepaticus, infects the livers of mice, causing a ... more A new murine Helicobacter species, Helicobacter hepaticus, infects the livers of mice, causing a progressive chronic active hepatitis culminating in hepatocellular tumors. To examine the role of chronic H. hepaticus infection in carcinogenesis, H. hepaticus-infected male infant mice of A/JCr strain were given a single ip dose of N-nitrosodimethylamine (NDMA). Noninfected A/J mice similarly treated with NDMA served as controls. The effect of hepatitis induced by H. hepaticus was studied for 64 wk. At 31-36 wk, the incidence of hepatocellular adenomas in infected mice was significantly higher than in noninfected mice (82 vs 52%; p = 0.05). The multiplicity of hepatocellular tumors was also significantly higher in infected mice compared to noninfected mice (3.2 ± 0.09 vs 0.09 ± 0.2; p = 0.03). At 51-64 wk, many (10/18) infected mice developed hepatocellular carcinomas while only 2 of 19 control mice developed such tumors ( p = 0.005). Overexpression of cyclin D was observed in hepatocy...
We are writing in response to comments that you have received from Drs Maioli and Fortino to our ... more We are writing in response to comments that you have received from Drs Maioli and Fortino to our recent manuscript published in the Breast Cancer Research and Treatment [1]. We are encouraged that our data describing the role of PKCd, MAPK/ERK, and p27 in anti-proliferative activity effects of inositol hexaphosphate (IP6) in breast cancer cells are in agreement with Drs Maioli and Fortino’s theory on PKCd role in cellular processes. We agree with their proposed model by which PKCd upon physiological activation inhibits ERK activity through direct phosphorylation and blockage of Raf-1, resulting in accumulation of p27. The authors further suggest that in the case of a strong pharmacological activation and/or forced expression of PKCd, the associated molecular events involve phosphorylation of ERK through effectors other than Raf-1, resulting in p27 degradation and p21 induction. Most of the literature reports are consistent with the PKCd having an anti-proliferative and a tumor suppressing activity in different cellular models. However, due to a several findings indicating the pro-proliferative and possibly co-oncogenic role of PKCd [2], it is rather difficult to reconcile its role in proliferation and survival. A recent comprehensive review by Jackson and Foster [3] indicates that PKCd regulates several molecular players involved in cellular processes. The most important partners to PKCd are molecules in Ras/Raf/MEK/ ERK pathway [4], which, when activated, have been shown to contribute to cellular proliferation and oncogenesis. Therefore, it appears that the status of some of the molecules in this pathway will determine whether activation of PKCd will lead to proliferation or to cell cycle arrest. Activated PKCd might cause indirect activation of ERK, and this could be an important component of its ability to positively regulate cellular proliferation [4,5]. What it is not clear is why and under which circumstances PKCd activates ERK. Jackson and Foster summarized that PKCd can contribute to ERK activation at several points in the Ras/Raf/MEK/ERK signaling pathway: (1) upstream of Ras, (2) downstream of Ras but upstream of Raf, and down-stream of Raf but upstream of MEK [3]. Our results on investigation of molecular mechanism of IP6 anti-proliferative effects in human breast cancer cell lines with different molecular background (MCF-7 and MDA-MB 231) clearly indicate that IP6 activity involves the activation and membrane translocation of PKCd (Figure 1) [1]. This presents a very interesting experimental model through which the interaction of PKCd and its partnering kinases could be investigated. In MCF-7 cells (estrogen receptor-positive, wild type Ras and p53) activation of PKCd by IP6 led to downregulation of ERK after 30 min of treatment [1]. However, in MDA-MB 231 cells (estrogen receptornegative, mutated K-Ras and p53) the activation of PKCd activity by IP6 treatment at the same dose caused an increase of activity of ERK1/ERK2, which was sustained from 2 min through 24 h. There was no change in the expression of total ERK1/ERK2 (Figure 2). In
Inositol hexaphosphate (IP6) is a naturally occurring polyphosphorylated carbohydrate with demons... more Inositol hexaphosphate (IP6) is a naturally occurring polyphosphorylated carbohydrate with demonstrated anti-proliferative and anti-cancer activity in mammary cells. We hypothesized that IP6 modulates cell cycle proteins by action on cytoplasmic signaling molecules. The effects of both pharmacological (2 mM) and physiological (100 microM) doses of IP6 on major PKC isoforms (PKCalpha, delta, epsilon, beta and zeta), PI3-K/Akt and ras/Erk1/2 were evaluated. Treatment of MCF-7 human breast cancer cells with 2 mM IP6 for 24 h caused a 3.1-fold increase in the expression of anti-proliferative PKCdelta. Similar results were observed with 100 microM IP6 at only 30-60 min post-treatment. IP6 also caused an increase in PKCdelta activity, shown by its translocation from cytosol to membrane. No changes in expression of PKC alpha, delta, epsilon, beta and zeta were detected. Additionally, IP6 caused a decrease of Erk1/2 and Akt activity. Among cell cycle control proteins, IP6 resulted in increased p27Kip1 protein levels and marked reduction of pRb phosphorylation. Specificity of the IP6 effects on p27Kip1 and pRb in MCF-7 cells (hormone-dependent) were additionally confirmed in highly invasive hormone-independent MDA-MB 231 breast cancer cells. Use of specific pharmaclogical inhibitors of PKC delta, MEK/Erk, and PI3K/Akt pathways indicated that the IP6-mediated effects on PKC delta were responsible for up-regulation of p27Kip, and pRb hypo-phosphorylation. In addition, IP6-induced apoptosis detected in MCF-7 cells appeared also to be PKC delta-dependent. Our data suggest potential usefulness of IP6 as a novel therapeutic modulator of PKC delta and p27Kip1, an important prognostic factor in human breast cancers.
We review the hepatocarcinogenic effects of fungal cultures of Fusarium verticillioides ( = Fusar... more We review the hepatocarcinogenic effects of fungal cultures of Fusarium verticillioides ( = Fusarium moniliforme) strain MRC 826 in male BD IX rats. Subsequent chemical analyses of the fumonisin B (FB) mycotoxin content in the culture material used and long-term carcinogenesis studies with purified FB 1 provide information about dose–response effects, relevance of hepatotoxicity during FB 1-induced carcinogenesis, and the existence of a no-effect threshold. Fumonisin intake levels of between 0.08 and 0.16 mg FB/100 g body weight (bw)/day over approximately 2 years produce liver cancer in male BD IX rats. Exposure levels < 0.08 mg FB/100 g bw/day fail to induce cancer, although mild toxic and preneoplastic lesions are induced. The nutritional status of the diets used in the long-term experiments was marginally deficient in lipotropes and vitamins and could have played an important modulating role in fumonisin-induced hepatocarcinogenesis. Short-term studies in a cancer initiation/...
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