Biomedical subjects

Matthew H Herynk

Publications and source records attributed to Matthew H Herynk.

6 recordsLinked to original sources

PubMed2006

Cooperative action of tamoxifen and c-Src inhibition in preventing the growth of estrogen receptor-positive human breast cancer cells.

It has long been appreciated that estrogenic signaling contributes to breast cancer progression. c-Src is also required for a number of processes involved in tumor progression and metastasis. We have previously identified the K303R mutant estrogen receptor alpha (ERalpha) that confers hypersensitivity to low levels of estrogen. Because ERalpha and c-Src have been shown to interact in a number of different systems, we wanted to evaluate the role of c-Src kinase in estrogen-stimulated growth and survival of ERalpha-positive breast cancer cells. MCF-7 cells stably expressing the mutant receptor showed increased c-Src kinase activity and c-Src tyrosine phosphorylation when compared with wild-type ERalpha-expressing cells. A c-Src inhibitor, AZD0530, was used to analyze the biological effects of pharmacologically inhibiting c-Src kinase activity. MCF-7 cells showed an anchorage-dependent growth IC50 of 0.47 micromol/L, which was increased 4-fold in the presence of estrogen. In contrast, cells stably expressing the mutant ERalpha had an elevated IC50 that was only increased 1.4-fold by estrogen stimulation. The c-Src inhibitor effectively inhibited the anchorage-independent growth of both of these cells, and estrogen was able to reverse these effects. When cells were treated with suboptimal concentrations of c-Src inhibitor and tamoxifen, synergistic inhibition was observed, suggesting a cooperative interaction between c-Src and ERalpha. These data clearly show an important role for ERalpha and estrogen signaling in c-Src-mediated breast cancer cell growth and survival. Here, we show that c-Src inhibition is blocked by estrogen signaling; thus, the therapeutic use of c-Src inhibitors may require inhibition of ERalpha in estrogen-dependent breast cancer.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2005

The guanine nucleotide exchange factor Tiam1 increases colon carcinoma growth at metastatic sites in an orthotopic nude mouse model.

Alterations in migration and adhesion are critical to invasion and metastasis. To examine signaling pathways important for colon tumor metastasis, cells of increased migratory potential from the low migratory SW480 human colorectal carcinoma parental cell line were biologically selected by serial migration through modified Boyden chambers. Several sublines were obtained with statistically significantly increased migration relative to the parental cell line. One highly migratory population was single-cell cloned and characterized. The migratory clones exhibit a four- to five-fold increase in protein and mRNA expression of T-lymphoma invasion and metastasis gene 1 (Tiam1), a guanine nucleotide exchange factor. To determine directly the role of Tiam1 in the migration of these migratory sublines, the parental SW480 cell line was transfected with a plasmid encoding the Tiam1 protein, and single cell clones were established. Ectopic expression of Tiam1 in these clones led to morphologic changes identical to biologically selected clones and increased migration. Finally, the implantation of clones that overexpress Tiam1 into the cecum of athymic mice resulted in tumor growth in the spleen, liver, and lung, whereas parental cells do not form tumors by this route of injection. These results demonstrate that overexpression of Tiam1 contributes to the metastatic phenotype of colon cancer cells.

Animals↗

PubMed2004

Estrogen receptor mutations in human disease.

As early as the 1800s, the actions of estrogen have been implicated in the development and progression of breast cancer. The estrogen receptor (ER) was identified in the late 1950s and purified a few years later. However, it was not until the 1980s that the first ER was molecularly cloned, and in the mid 1990s, a second ER was cloned. These two related receptors are now called ERalpha and ERbeta, respectively. Since their discovery, much research has focused on identifying alterations within the coding sequence of these receptors in clinical samples. As a result, a large number of naturally occurring splice variants of both ERalpha and ERbeta have been identified in normal epithelium and diseased or cancerous tissues. In contrast, only a few point mutations have been identified in human patient samples from a variety of disease states, including breast cancer, endometrial cancer, and psychiatric diseases. To elucidate the mechanism of action for these variant isoforms or mutant receptors, experimental mutagenesis has been used to analyze the function of distinct amino acid residues in the ERs. This review will focus on ERalpha and ERbeta alterations in breast cancer.

Alternative Splicing↗

PubMed2003

Reduced c-Met expression by an adenovirus expressing a c-Met ribozyme inhibits tumorigenic growth and lymph node metastases of PC3-LN4 prostate tumor cells in an orthotopic nude mouse model.

PURPOSE: The expression of c-Met, the receptor protein tyrosine kinase for hepatocyte growth factor/scatter factor, frequently increases during prostate tumor progression. However, whether reduced c-Met expression inhibits tumor growth and metastasis has not been ascertained. EXPERIMENTAL DESIGN: c-Met expression was reduced by infection of an adenovirus expressing a c-Met ribozyme into the highly metastatic human prostate cancer cell line PC3-LN4. In vitro, effects on c-Met, Akt, and extracellular signal-regulated kinase 1/2 expression and phosphorylation, Src expression and activity, and vascular endothelial growth factor expression were determined, as were effects on cell migration and invasion. Prostate tumor formation and metastasis to regional lymph nodes in nude mice were examined after both ex vivo and in vivo infection of cells. RESULTS: Infection of PC3-LN4 cells with the Ad-c-Met-expressing ribozyme decreased steady-state c-Met levels, decreased Src kinase activity, decreased vascular endothelial growth factor expression, and decreased migration and invasion versus the pU1 (control) virus. Significant inhibition of tumorigenicity (histologically confirmed tumors in only 1 of 10 mice) and consequent lymph node metastasis were observed upon ex vivo infection of Ad-c-Met. Similarly, gene therapy experiments led to complete inhibition of tumor growth in 7 of 8 mice. CONCLUSIONS: Reduction in c-Met expression substantially inhibits both tumor growth and lymph node metastasis of PC3-LN4 cells in orthotopic nude mouse models. Therefore, targeting the c-Met signaling pathways may be important in controlling tumor growth and metastasis in human prostate cancers.

Adenoviruses, Human↗

PubMed2003

Down-regulation of c-Met inhibits growth in the liver of human colorectal carcinoma cells.

Overexpression of c-Met, the protein tyrosine kinase receptor for the hepatocyte growth factor/scatter factor, has been implicated in the progression and metastasis of human colorectal carcinoma. To examine the role of c-Met on in vitro and in vivo growth of human colon tumor cell lines, stable subclones of the high metastatic human colorectal carcinoma cell line, KM20, isolated from a Dukes' D patient, with reduced c-Met expression were obtained after transfection with a c-Met-specific targeting ribozyme. The subclones were only modestly reduced in c-Met expression because of c-Met playing an important role in cellular survival. However, a 60-90% reduction in basal c-Met autophosphorylation and kinase activity were observed. Correlating with the reduction in c-Met kinase activity, subclones with reduced c-Met expression had significantly reduced in vitro growth rates and soft-agar colony-forming abilities. The in vivo growth of these cells was examined at both the ectopic SQ site and the orthotopic site of metastatic growth, the liver. SQ growth was delayed significantly in the c-Met down-regulated clones compared with controls, with tumors growing on loss of the ribozyme construct. In contrast, tumor incidence was significantly reduced when the c-Met down-regulated cells were grown in the orthotopic liver site. Thus, c-Met activation may be important in metastatic growth of colon tumor cells in the liver. Collectively these data demonstrate that a small reduction in c-Met protein levels leads to profound biological effects, and potential c-Met inhibitors may be of therapeutic value in treatment of colon cancer.

Adenoviridae↗

PubMed2003

Activation of c-Met in colorectal carcinoma cells leads to constitutive association of tyrosine-phosphorylated beta-catenin.

Increased expression and/or activity of c-Met, the receptor protein tyrosine kinase for hepatocyte growth factor/scatter factor, occurs commonly during colon tumor progression. To examine potential roles for c-Met in promoting metastasis, we compared the colon tumor cell line KM12C with low metastatic potential to the isogenic variants KM,12L4 and KM12SM with high metastatic potential. KM12C cells express c-Met with low levels of tyrosine phosphorylation in the absence of HGF. The high metastatic cells express a c-Met that is constitutively tyrosine phosphorylated, they have increased colony formation, and are minimally responsive to HGF relative to the parental cells. Tyrosine-phosphorylated beta-catenin was constitutively associated with c-Met in the more metastatic cells, but was inducible only after HGF addition in the less metastatic cells. Functions mediated by beta-catenin, including cell-cell adhesion and migration, and activation of the tcf (T-cell factor) family of transcription factors, were also elevated in the more metastatic KM12SM and L4 cells. Furthermore, analysis of the known tcf transcriptional target genes, cyclin D1, c-Myc, and uPAR, demonstrated increased expression in the high metastatic cells, correlating with the levels of tcf activity. Collectively, these results suggest that endogenous activation of c-Met in highly metastatic KM12SM CRC cells results in increased survival and growth under anchorage independent conditions, increased in vitro migration, and elevated levels of tcf target genes. Thus, beta-catenin association with activated c-Met may contribute to a more aggressive liver metastatic phenotype of these cells.

Blotting, Western↗