Transforming growth factors and related peptides in gastrointestinal neoplasia

SFKs/p38 Pathway is Involved in Radicular Pain by Promoting Spinal Expression of Pro-Inflammatory Cytokines in a Rat Model of Lumbar Disc Herniation

STUDY DESIGN

A controlled, randomized, animal study.

OBJECTIVE

The aim of this study was to investigate the role of src-family kinases/p38 pathway in a rat model of lumbar disc herniation (LDH).

SUMMARY OF BACKGROUND DATA

LDH always generates radicular pain, and the mechanism remains unclear. We have reported that spinal src-family kinases (SFKs) may be involved in the process, but the downstream mechanism needs further investigation.

METHODS

LDH was induced by implantation of autologous nucleus pulposus (NP), harvest from the tail, in lumbar 4/5 spinal nerve roots of rat. Von Frey filaments and radiant heat tests were performed to determine mechanical and thermal pain threshold respectively. Basso, Beattie, and Bresnahan (BBB) scale was assessed to test the locomotor function. The protein level of p-SFKs, t-SFKs, p-p38, t-p38 in spinal cord was examined by western blotting analysis. Cellular location of p-p38 was determined by immunochemistry staining. Spinal tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, and IL-6 levels were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Rats with NP implantation showed persistent ipsilateral mechanical allodynia and thermal hyperalgesia, which manifested as obvious decrease of paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). BBB scale indicated the locomotor function of hindpaws in rats with NP implantation kept intact. Western blotting and immunohistochemistry staining revealed that phosphorylated SFKs (p-SFKs) and phosphorylated p38 MAPK (p-p38) were sequentially upregulated in ipsilateral spinal dorsal horn, but not in contralateral side of rats with NP. Intrathecal delivery of SFKs inhibitor reduced spinal p-p38 expression. Both SFKs and p38 inhibitors alleviated pain behaviors in a dose-responsive manner without disturbing locomotor function and reduced spinal expression of TNF-α, IL-1β, and IL-6 in rats with NP.

CONCLUSION

Spinal SFKs contribute to radicular pain by activation of p38 MAPK and increasing pro-inflammatory cytokines expression in rats with NP implantation. Targeting SFKs/p38 pathway may be helpful for alleviating radicular pain.

LEVEL OF EVIDENCE

N/A.

Src/p38 MAPK pathway in spinal microglia is involved in mechanical allodynia induced by peri-sciatic administration of recombinant rat TNF-α

Our previous work has shown that peri-sciatic administration of recombinant rat TNF-α (rrTNF) induces mechanical allodynia and up-regulation of TNF-α in the spinal dorsal horn of rats; however, the underlying mechanisms remain unknown. In the current study, we found that the levels of phosphorylated Src-family kinases (p-SFKs) and phosphorylated p38 mitogen-activated protein kinase (p-p38 MAPK) were significantly increased in bilateral lumbar spinal dorsal horn on day 3 after rrTNF administration. Double immunofluorescence staining revealed that p-SFKs and p-p38 MAPK were nearly restricted to the microglia. Intrathecal delivery of SFKs inhibitor PP2 or p38 MAPK inhibitor SB203580, started 30 min before rrTNF administration and given once daily thereafter for 7 days, blocked mechanical allodynia in bilateral hind paws and increase of TNF-α expression in the spinal dorsal horn. Moreover, PP2 inhibited the up-regulation of p-p38 MAPK induced by rrTNF. We also found that intrathecal injection of TNF-α neutralization antibody alleviated mechanical allodynia in bilateral hind paws and suppressed up-regulation of p-SFKs and p-p38 MAPK. These results suggest that activation of the SFKs/p38 MAPK pathway in microglia and subsequent TNF-α expression in the spinal dorsal horn may contribute to the mechanical hyperalgesic state induced by peri-sciatic administered rrTNF.

Sulindac metabolites induce proteosomal and lysosomal degradation of the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) is a member of the ErbB family of receptor tyrosine kinases. In response to ligand, EGFR is internalized and degraded by the ubiquitin-proteasome/lysosome pathway. We previously reported that metabolites of the nonsteroidal anti-inflammatory drug sulindac downregulate the expression of EGFR and inhibit basal and EGF-induced EGFR signaling through extracellular signal-regulated kinase 1/2. We now have evaluated the mechanisms of sulindac metabolite-induced downregulation of EGFR. EGF-induced downregulation of EGFR occurs within 10 minutes and lasts for 24 hours. By contrast, downregulation of EGFR by sulindac sulfide and sulindac sulfone was first evident at 4 and 24 hours, respectively, with maximal downregulation at 72 hours. Pretreatment with either the lysosomal inhibitor chloroquine or the proteosomal inhibitor MG132 blocked sulindac metabolite-induced downregulation of EGFR. Sulindac metabolites also increased the ubiquitination of EGFR. Whereas sulindac metabolites inhibited phosphorylation of EGFR pY1068, they increased phosphorylation of EGFR pY1045, the docking site where c-Cbl binds, thereby enabling receptor ubiquitination and degradation. Immunofluorescence analysis of EGF and EGFR distribution confirmed the biochemical observations that sulindac metabolites alter EGFR localization and EGFR internalization in a manner similar to that seen with EGF treatment. Expression of ErbB family members HER2 and HER3 was also downregulated by sulindac metabolites. We conclude that downregulation of EGFR expression by sulindac metabolites is mediated via lysosomal and proteosomal degradation that may be due to drug-induced phosphorylation at pY1045 with resultant ubiquitination of EGFR. Thus, sulindac metabolite-induced downregulation of EGFR seems to be mediated through mechanism(s) similar, at least in part, to those involved in EGF-induced downregulation of EGFR.

Smad4-mediated TGF-beta signaling in tumorigenesis

Transforming growth factor-β (TGF-β) family members exert their function via specific type I and type II serine/threonine kinase receptors and intracellular Smad transcription factors, including the common mediator Smad4. The dual effects of TGF-β signaling on tumor initiation and progression are cell-specific and yet to be determined under distinct contexts. A number of genetically manipulated mouse models with alterations in the TGF-β pathway genes, particularly the pivotal Smad4, revealed that these genes play crucial functions in maintaining tissue homeostasis and suppressing tumorigenesis. Loss of Smad4 plays a causal role in initiating squamous cell carcinomas of skin and upper digestive tract as well as adenocarcinomas of gastrointestinal tract. However, for some cancers like pancreatic and cholangiocellular carcinomas, Smad4 deficiency does not initiate the tumorigenesis but acts as a promoter to accelerate or synergize the development and progression of cancers that are started by other oncogenic pathways. Intriguingly, emerging evidences from mouse models have highlighted the important roles of non-cell autonomous effects of Smad4-mediated TGF-β signaling in the inhibition of oncogenesis. All these data have greatly deepened our understanding of molecular mechanisms of cell-autonomous and non-cell autonomous effect of Smad4-mediated TGF-β signaling in suppressing carcinogenesis, which may facilitate the development of successful therapies targeting TGF-β signaling for the treatment of human cancers.

Vascular endothelial growth factor and neo-angiogenesis in H. pylori gastritis in humans

Host response plays a major role in the pathogenesis of Helicobacter pylori-induced gastroduodenal disease including adenocarcinoma of the distal stomach. Vascular endothelial growth factor (VEGF) is an important modulator of gastric mucosal repair and is overexpressed in gastric cancer. The present study sought to evaluate the expression of VEGF in the gastric mucosa of H. pylori-infected and H. pylori-non-infected dyspeptic patients. Fifteen H. pylori-infected and 15 H. pylori-non-infected dyspeptic patients were studied. Diagnosis of H. pylori infection was based on rapid urease test and histology. VEGF protein expression was assessed by western blotting. VEGF mRNA expression was assessed by RT-PCR. VEGF localization in the gastric mucosa and neo-angiogenesis were determined by immunohistochemistry. VEGF protein and mRNA expression was significantly greater in H. pylori-infected than in non-infected patients. Immunohistochemistry showed that VEGF expression was more intense in the gastric gland compartment of H. pylori-infected mucosa than in the non-infected mucosa. The increase in VEGF expression was associated with a significant increase in neo-angiogenesis as assessed by determination of CD34-positive micro-vessels. H. pylori gastritis is therefore associated with up-regulation of VEGF expression, which parallels the increased formation of blood vessels in the gastric mucosa. It is postulated that increased VEGF expression and neo-angiogenesis may contribute to H. pylori-related gastric carcinogenesis.

The epidermal growth factor receptor as a target for colorectal cancer therapy

The epidermal growth factor receptor (EGFR) is the prototypical member of the erbB receptor family. The EGFR axis is activated by a variety of ligands that are crucial in the formation and propagation of many tumors, including colorectal cancer, through their effects on cell signaling pathways, cellular proliferation, control of apoptosis, and angiogenesis. The importance of the EGFR axis in tumorigenesis and tumor progression makes it an attractive target for the development of anticancer therapies. A variety of targeting strategies to exploit the role of EGFR in tumors have been employed. The most highly developed of these anti-EGFR approaches are the monoclonal antibodies and the tyrosine kinase inhibitors (TKIs). Clinical evaluations of these compounds have yielded some promising results. The role of the EGFR axis in colorectal cancer formation and progression is reviewed and the clinical development of these anticancer EGFR-targeted drugs is reviewed and updated.

Bile acid induced gene expression in LT97 colonic adenoma cells

LT97 human colonic adenoma cells reflecting early premalignant genotype and growth characteristics have been posed to tumor promoting bile acids in order to identify marker genes that permit identification of tumor promoters in vitro. Physiologically relevant concentrations of desoxycholate (DOC) and chenodesoxycholate (CDC) upregulated expression of c-fos and COX-2 in a concentration- and time-dependent manner. Transient induction of c-fos was seen with the non-promoting taurodesoxycholate (TDOC) as well as DOC, however extended induction at 3 h was only achieved by DOC and CDC reaching 3-6-fold as compared to the control. Stimulation of COX-2 expression was completely specific for the tumor promoting analogs DOC and CDC. It was about 4-fold in the 80 microM DOC and CDC groups after 3 h and increased to 12- and 7-fold respectively after 6 h. Expression of VEGF was stimulated 4-5-fold in the tumor promoter (DOC and CDC) groups and about 2-fold in the non-promoting controls TDOC and GCDC. At later times the tumor promoter specific difference was lost. Our results show that all three genes are modulated in a tumor promoter dependent way and that their upregulation in LT97 adenoma cells can be used for in vitro testing of colon tumor promoters and chemopreventive compounds.

Review article: inflammation-related promotion of gastrointestinal carcinogenesis--a perigenetic pathway

Chronic inflammation has been reported to accelerate neoplasmas in gastrointestinal tract. Certain bacteria including Helicobacter pylori directly interact with host cells, induce proinflammatory cytokines and stimulate production of free radicals. Free radicals cause mutations in target cells so that neoplastic clones are established. Accumulation of such genetic alterations may cause malignant transformation of some established clones. In addition, inflammatory alterations may promote growth, expansion and invasion of gastrointestinal epithelial cells. The latter changes caused by inflammation may occur even without further genetic mutations or epigenetic alterations, and therefore may be categorized as 'perigenetic alterations' of neoplastic cells. For an example, tumour necrosis factor alpha (TNF-alpha) plays pivotal roles not only in the reduction but also in the growth, invasion and metastases of certain neoplasmas. Our studies show that TNF-alpha increases intracellular radical production, degradates E-cadherin / beta-catenin complex and promotes dispersion and migration in epithelial cells transformed with an activated src oncogene (v-src). These data indicate that an inflammatory cytokine induces the malignant potential of src-activated neoplastic cells. Interestingly, TNF-alpha also induced these phenotypic changes in nonmutated cells whose c-Src was activated by TGF-alpha, suggesting that the invasive properties of the cell were not necessarily related to gene mutation. Furthermore, certain radical scavengers suppressed the invasive phenotype of the cells. These results indicate that perigenetic alterations are an important target of pharmacological intervention of carcinogenesis.

Overexpression of cyclooxygenase 2 in hamartomatous polyps of Peutz-Jeghers syndrome

OBJECTIVE

Peutz-Jeghers syndrome (PJS) is an autosomal-dominant hamartomatous polyposis syndrome. Affected individuals are at risk for intestinal and extraintestinal malignancies. Prostaglandins and polyamines are small molecules believed to be important in tumor formation and growth. Cyclooxygenase (COX) and ornithine decarboxylase (ODC) are key enzymes in the prostaglandin and polyamine biosynthetic pathways, respectively. The aim of this study was to measure and compare COX-1 and COX-2 expression in normal and hamartomatous tissue of PJS patients.

METHODS

We measured COX-1 and COX-2 protein expression in normal and hamartomatous GI tissues from affected PJS individuals and compared it with that in normal controls. COX-2 RNA in these tissues was also measured and compared by reverse transcription polymerase chain reaction (PCR). In addition, COX-2 expression was detected in tissue slides by immunostaining. ODC activity was measured between normal and hamartomatous tissues of PJS compared with control tissues.

RESULTS

COX-1 expression was similar in normal and control GI tissues. In contrast, COX-2 overexpression was noted in hamartomatous polyp tissue from PJS patients compared with normal control and PJS tissue. COX-2 expression by reverse transcription PCR was 10-fold greater in a hamartoma compared with other tissues. COX-2 expression was noted in the epithelial cells of hamartomatous polyps, and also coursing throughout the stromal tissue of the lamina propria, including muscle cells. ODC activity was similar in the tissues studied.

CONCLUSIONS

Selective COX-2 overexpression was noted in hamartomatous polyp tissue from PJS individuals. The results of the study provide an avenue for possible effective chemoprevention of polyp formation and growth in PJS.

Up-regulation of heparin binding epidermal growth factor-like growth factor and amphiregulin expression in Helicobacter pylori-infected human gastric mucosa

BACKGROUND

Host response plays a major role in pathogenesis of Helicobacter pylori-induced gastroduodenal disease including adenocarcinoma of distal stomach. Epidermal growth factor-related growth factors are important modulators of gastric homeostasis in normal and damaged gastrointestinal mucosa.

AIM

To evaluate expression of heparin binding epidermal growth factor and amphiregulin in antral mucosa of Helicobacter pylori-infected and non-infected dyspeptic patients and to correlate levels of heparin binding-epidermal growth factor and amphiregulin mRNA with mitogenic activity of gastric epithelial cells.

METHODS

A total of 10 Helicobacter pylori-infected and 15 Helicobacter pylori non-infected (10 with and 5 without gastritis) dyspeptic patients were studied. Diagnosis of Helicobacter pylori infection was based on rapid urease test and histology. Heparin binding-epidermal growth factor and amphiregulin mRNA expression in antral mucosa were assessed by reverse transcriptase-polymerase chain reaction. Protein expression and localization of both peptides were determined by immunohistochemistry. Mitogenic activity of antral gastric mucosa was assessed by determination of proliferating cell nuclear antigen labelling index by immunohistochemistry.

RESULTS

Heparin binding-epidermal growth factor and amphiregulin mRNA expression increased in Helicobacter pylori-infected vs Helicobacter pylori non-infected patients. Heparin binding-epidermal growth factor and amphiregulin immunostaining was more intense and deeper in gastric gland compartment in infected mucosa than in non-infected mucosa. Increase in heparin binding-epidermal growth factor and amphiregulin mRNA expression significantly correlated with increase in proliferating cell nuclear antigen labelling index.

CONCLUSIONS

Helicobacter pylori gastritis is associated with up-regulation of heparin binding-epidermal growth factor and amphiregulin which correlates with increased mitogenic activity of gastric mucosa. Increased heparin binding-epidermal growth factor and amphiregulin expression is postulated to contribute to reparative response of gastric mucosa to Helicobacter pylori infection.

New Directions in the Treatment of Cancer: Inhibition of Signal Transduction

In recent years, it has become increasingly apparent that proteins regulated by activated oncogenes or mutated tumor suppressor genes are responsible for the transformation of normal cells to malignant cells as well as for malignant characteristics such as uncontrolled cellular proliferation and the development of metastases. These proteins may be soluble factors, receptors on cell surfaces, or intracellular enzymes that produce signals that stimulate cellular development or proliferation. This process is called signal transduction .In many cases, increased amounts of these proteins have been demonstrated in cancer cells (over normal cells) and have been found to carry prognostic significance. New approaches in cancer treatment are being designed to block such proteins; this approach is termed signal transduction inhibition. !Specific protein targets that anticancer therapies have been developed to inhibit include epidermal growth factor receptors, tyrosine kinase, farnesyl transferase, and various promoters of angiogenesis.

The PEA3 subfamily of Ets transcription factors synergizes with beta-catenin-LEF-1 to activate matrilysin transcription in intestinal tumors

The matrix metalloproteinase matrilysin (MMP-7) is expressed in the tumor cells of a majority of mouse intestinal and human colonic adenomas. We showed previously that matrilysin is a target gene of beta-catenin-Tcf, the transcription factor complex whose activity is thought to play a crucial role in the initiation of intestinal tumorigenesis. Here we report that overexpression of a stable mutant form of beta-catenin alone was not sufficient to effect expression of luciferase from a matrilysin promoter-luciferase reporter plasmid. However, cotransfection of the reporter with an expression vector encoding the PEA3 Ets transcription factor, or its close relatives ER81 and ERM, increased luciferase expression and rendered the promoter responsive to beta-catenin-LEF-1 as well as to the AP-1 protein c-Jun. Other Ets proteins could not substitute for the PEA3 subfamily. Luciferase activity was induced up to 250-fold when PEA3, c-Jun, beta-catenin, and LEF-1 were coexpressed. This combination of transcription factors was also sufficient to induce expression of the endogenous matrilysin gene. Furthermore, all matrilysin-expressing benign intestinal tumors of the Min mouse expressed a member of the PEA3 subfamily, as did all human colon tumor cell lines examined. These data suggest that the expression of members of the PEA3 subfamily, in conjunction with the accumulation of beta-catenin in these tumors, leads to coordinate upregulation of matrilysin gene transcription, contributing to gastrointestinal tumorigenesis.

Increased serum levels of transforming growth factor-alpha in patients with colorectal cancer

PURPOSE

This study was conducted to investigate the serum levels of transforming growth factor-alpha in patients with colorectal cancer and to investigate the clinical significance of these levels in association with tumor stage and histologic differentiation. Also, serum levels of transforming growth factor-alpha were measured after curative surgical resection.

METHODS

Serum levels of transforming growth factor-alpha were measured in 42 consecutive patients with colorectal cancer before surgery, in 21 patients after surgical resection (part of the 42 preoperative patients), and in 20 healthy volunteers. We used TGF-alpha Assay.

RESULTS

Serum levels of transforming growth factor-alpha in patients with colorectal cancer were significantly higher than in the healthy control group (P = 0.001). Significant elevations in serum levels of transforming growth factor-alpha were found in 50 percent (21/42) of patients with colorectal cancer when the mean + 2 standard deviations (80.4 pg/ml) of the control group were used as the upper limit of the normal range. Serum levels of transforming growth factor-alpha tended to decrease with increasing tumor size (n = 31; r = -0.52; P = 0.002). Serum levels of transforming growth factor-alpha before surgery (89.7 +/- 44.4 pg/ml; n = 21) significantly decreased to 60.3 +/- 19.8 pg/ml after surgical resections of tumors (P = 0.017). Serum levels of transforming growth factor-alpha completely decreased to the same serum levels of the control group after surgical resections in all patients who had serum levels of transforming growth factor-alpha greater than mean + 2 standard deviations (80.4 pg/ml) of the control group preoperatively (n = 11; P = 0.002).

CONCLUSIONS

Levels of preoperative transforming growth factor-alpha in patients with colorectal cancer appeared to be higher than levels measured in control subjects. Serum levels of transforming growth factor-alpha before surgery significantly decreased after surgical resections of tumors. Additional studies are warranted to determine if serum levels of transforming growth factor-alpha may be useful as a potential biomarker in the management of patients with colorectal cancer.

Clinical relevance of transforming growth factor-beta 1 in the urine of patients with hepatocellular carcinoma

To assess the clinical relevance of transforming growth factor-beta 1 (TGF-beta 1) in the urine of patients with hepatocellular carcinoma (HCC), TGF-beta 1 was measured, by radioimmunoassay, in 140 patients with HCC, 50 cirrhotic patients, 30 patients with chronic active hepatitis, and 50 healthy controls. The results indicate that there were significantly increased urinary TGF-beta 1 levels in patients with HCC. Raised TGF-beta 1 levels were associated, in a dose-related fashion, with increased risk for development of HCC (odds ratio, 1.05, 95% confidence interval, 1.03-1.07). HCC patients with raised TGF-beta 1 levels had shorter survival than those with normal TGF-beta 1 levels (p = 0.038). TGF-beta 1 levels decreased after successful anticancer therapy (p < 0.0001). There was an inverse correlation between TGF-beta 1 and serum alpha-fetoprotein (AFP) (r = -0.199, p < 0.04). Receiver operating characteristics (ROC) curve analysis indicated that parallel determination of TGF-beta 1 and AFP significantly increased the sensitivity and diagnostic accuracy, with a high specificity. In conclusion, raised urinary TGF-beta 1 was associated with HCC development. It is a predictor of poor prognosis, and a tumor marker for diagnosis and therapeutic follow-up of HCC.

Epidermal growth factor expression in human colon and colon carcinomas: anti-sense epidermal growth factor receptor RNA down-regulates the proliferation of human colon cancer cells

Human colon cancer cell lines express epidermal growth factor (EGF) mRNA, secrete EGF and may respond to it via the cell-surface EGF receptor (EGFR). Expression of these molecules in human colon and colon tumor, however, is not clear. Reverse transcription-polymerase chain reaction (RT-PCR) analyses of RNA prepared from paired normal human colon and colon tumor samples from 12 individuals followed by Southern blotting analyses of the RT-PCR products revealed a major fragment of 527 bp and a minor fragment of 404 bp that hybridized to a human EGF cDNA probe under stringent conditions. Identical results were obtained from 8 human colon cancer cell lines. Cloning and sequencing of PCR products confirmed that both fragments were from the human EGF gene; the 527-bp fragment corresponded exactly to nucleotides 2,891 to 3,417 of the human EGF mRNA reported by others. A deletion of 123 nucleotides (nucleotides 3,172 to 3,294) was found in the 404-bp fragment. Immunohistochemical studies using cyostat sections of human colon specimens showed that EGF was expressed in the human colon and that expression was restricted to the epithelial colonic crypt cells and epithelium-derived cancer cells. Since EGF and EGF-related molecules are potent mitogens that mediated their effect through the EGFR, we also determined the efficacy of anti-sense EGFR RNA in circumventing the EGFR-related pathway of proliferation. Expression of anti-sense EGFR RNA, by transfection with an inducible anti-sense EGFR expression vector, down-regulated cell-surface EGFR expression and proliferation of these cells and their ability to grow in soft agar. Anti-sense EGFR RNA was found to be an anti-proliferative agent in both relatively non-aggressive and highly aggressive human colon cancer cells.

Genetics, molecular biology and colorectal cancer

Colorectal cancer (CRC) develops through several histologically well-defined stages, reflecting the sequential acquisition of genetic alterations. Several frequently mutated genes have been identified which probably contribute to the development of both hereditary and sporadic cancer (reviewed in Bishop and Thomas, 1990; Fearon and Vogelstein, 1990; Fearon and Jones, 1992; Hamilton, 1992). Several generalizations emerge from this work. Mutations are observed in the earliest detectable stages of cancer development. Specific genes tend to be mutated in a given order, but it is the accumulation of a critical number of lesions which governs the appearance of neoplasia. Mutations actively promote neoplastic character by activating oncogenes and eliminate restraints on neoplastic character by inactivating tumour suppressor genes.