Activation of ErbB3-PI3-kinase pathway is correlated with malignant phenotypes of adenocarcinomas

Prevalence of Her3 in gastric cancer and its association with molecular prognostic markers: a Saudi cohort based study

Her 3 is a member of epidermal growth factor receptors. Mutated, oncogenic Her3 is reported in gastric and colonic cancers with emerging evidence that Her3 can be a potential target for molecular therapies. There is a paucity of studies regarding Her3 and its prognostic implications in gastric cancer in our region. In this study, we evaluated prevalence of Her3 in gastric cancer, in a Saudi cohort of cases, along with its association with prognostic markers p53 and Ki-67. The study was conducted in Department of Pathology of King Fahd Hospital of Imam Abdulrahman Bin Faisal University, Dammam, KSA. Fifty cases of gastric carcinoma were selected from the pathology files that fulfilled the inclusion criteria. Clinico-pathological parameters, Laurens histological classification, and immunohistochemical staining for Her3, p53, and Ki-67 were done. Her 3 positive cases were also evaluated for Her-2neu co-expression. Her3 positivity was seen in 16% (n = 8) out of a total of 50 cases. The median age of presentation was 44 years. Within Her3 positive cases, a female preponderance of 63% (n = 5), presence of high grade tumors in 75% (n = 6), diffuse gastric carcinoma in 63% (n = 5), diffuse to focal p53 positivity in 63% (n = 5), and a high to moderate Ki-67 proliferation index in 75% (n = 6) of cases was seen. Her3 expression was independent of Her-2neu status. Her3 prevalence of 16% with a median age of 44 years at presentation was less than in other reported studies, highlighting the concept of ethnic and regional variation in tumor characteristics. Her3 association with diffuse gastric carcinoma, high grade tumors, diffuse to focal p53 positivity and high to moderate Ki-67 proliferation index points towards a more aggressive clinical behavior.

The significance of scirrhous gastric cancer cell lines: the molecular characterization using cell lines and mouse models

Scirrhous gastric cancer (SGC) exhibits aggressiveness of the rapid infiltrating tumor cells with abundant fibroblasts. Experimental studies using SGC cell lines have obtained useful information about this cancer. Our literature search divulged a total of 18 SGC cell lines; two cell lines were established from primary SGC and the other lines were established from a metastatic lesion of SGC. Fibroblast growth factor receptor 2 (FGFR2) and transforming growth factor-beta receptor (TβR) are linked to the rapid development of SGC. Cross-talk between the cancer cells and cancer-associated fibroblasts (CAFs) has been shown to contribute to the progression of SGC. Chemokine (C-X-C motif) receptor 1 (CXCR1) from SGC cells might be associated with the abundant CAFs in cancer microenvironments. The in vivo models established using SGC cell lines are expected to serve as a useful tool for the development of drugs such as FGFR2 inhibitors, TβR inhibitors, and CXCR1 inhibitors, which might be promising as SGC treatments. However, the number of available SGC cell lines is insufficient for the clarification of the entire biologic behavior of SGC. Since the mechanisms responsible for the characteristic aggressiveness of SGC are not fully elucidated, the establishment of new SGC cell lines could help clarify the biological behavior of SGC and contribute to its treatment.

Phosphoinositide 3-Kinase Signalling Pathways in Tumor Progression, Invasion and Angiogenesis

Aims and background

The PI3 kinase signalling pathway is now accepted as being at least as important as the ras-MAP kinase pathway in cell survival and proliferation, and hence its potential role in cancer is of great interest1. The purpose of this review is briefly to examine evidence for an involvement of PI3K in human cancers, discuss the mechanisms by which its activation promotes tumor progression, and consider its utility as a novel target for anticancer therapy.

Methods and study design

A Medline review of recent literature concerning the role of PI3 kinase in tumor progression -mechanisms of action and clinical implications.

Results

Evidence is presented that misregulation of the PI3 kinase pathway is a feature of many common cancers, either by loss of the suppressor protein PTEN, or by constitutive activation of PI3 kinase isoforms or downstream elements such as AKT and mTOR. This activation potentiates not only cell survival and proliferation, but also cytoskeletal deformability and motility; key elements in tumor invasion. In addition the PI3K pathway is implicated in many aspects of angiogenesis, including upregulation of angiogenic cytokines due to tumor hypoxia or oncogene activation and endothelial cell responses to them. These cytokines signal though receptors such as VEGF-R, FGF-R and Tie-2 and potentiate processes essential for neoangiogenesis including cell proliferation, migration, differentiation into tubules and “invasion” of these capillary sprouts into extracellular matrix (ECM).

Conclusions

A more complete understanding of the role of the PI3 kinase pathway in cancer will lead the way to the development of more potent and selective inhibitors which should be a useful adjunct to conventional therapies, potentially interfering with tumor progression at several pivotal points; in particular cell survival, invasion and angiogenesis.

Signet-ring Cells in the Skin: A Case of Late-onset Cutaneous Metastasis of Gastric Carcinoma and a Brief Review of Histological Approach

Up to 10% of patients with visceral malignancies develop skin metastases during their clinical course and these metastases constitute about 2% of all skin cancers. Skin metastasis may be the first sign of a clinically silent visceral cancer or represent recurrence of an internal malignancy. In both situations, they are associated with poor prognosis, which can partly be attributed to underdiagnosis. In this paper, a case of relapsing gastric adenocarcinoma, which manifested itself as asymptomatic cutaneous papules and nodules on a patient's head and neck, is reported and histopathological approach to the cutaneous lesions containing signet-ring cell is briefly reviewed.

Exploring Missense Mutations in Tyrosine Kinases Implicated with Neurodegeneration

Protein kinases are one of the largest families of evolutionarily related proteins and the third most common protein class of human genome. All the protein kinases share the same structural organization. They are made up of an extracellular domain, transmembrane domain and an intra cellular kinase domain. Missense mutations in these kinases have been studied extensively and correlated with various neurological disorders. Individual mutations in the kinase domain affect the functions of protein. The enhanced or reduced expression of protein leads to hyperactivation or inactivation of the signalling pathways, resulting in neurodegeneration. Here, we present extensive analyses of missense mutations in the tyrosine kinase focussing on the neurodegenerative diseases encompassing structure function relationship. This is envisaged to enhance our understanding about the neurodegeneration and possible therapeutic measures.

Immunohistochemical analysis of RTKs expression identified HER3 as a prognostic indicator of gastric cancer

Standard treatment in Japan for the 13th Japanese Gastric Cancer Association stage II/III advanced gastric cancer is postoperative adjuvant S-1 administration after curative surgery. High expression of receptor type tyrosine kinases (RTKs) has repeatedly represented poor prognosis for cancers. However it has not been demonstrated whether RTKs have prognostic relevance for stage II/III gastric cancer with standard treatment. Tumor tissues were obtained from 167 stage II/III advanced gastric cancer patients who underwent curative surgery and received postoperative S-1 chemotherapy from 2000 to 2010. Expression of the RTKs including EGFR, HER2, HER3, IGF-1R, and EphA2 was analyzed using immunohistochemistry (IHC). Analysis using a multivariate proportional hazard model identified the most significant RTKs that represented independent prognostic relevance. When tumor HER3 expression was classified into IHC 1+/2+ (n = 98) and IHC 0 (n = 69), the cumulative 5-year Relapse Free Survival (5y-RFS) was 56.5 and 82.9%, respectively (P = 0.0034). Significant prognostic relevance was similarly confirmed for IGF-1R (P = 0.014), and EGFR (P = 0.030), but not for EphA2 or HER2 expression. Intriguingly, HER3 expression was closely correlated with IGF-1R (P < 0.0001, R = 0.41), and EphA2 (P < 0.0001, R = 0.34) expression. Multivariate proportional hazard model analysis identified HER3 (IHC 1+/2+) (HR; 1.53, 95% CI, 1.11–2.16, P = 0.0078) as the sole RTK that was a poor prognostic factor independent of stage. Of the 53 patients who recurred, 40 patients (75.5%) were HER3-positive. Thus, of the RTKs studied, HER3 was the only RTK identified as an independent prognostic indicator of stage II/III advanced gastric cancer with standard treatment.

Mechanisms behind signet ring cell carcinoma formation

Signet ring cell carcinomas are highly malignant dedifferentiated adenocarcinomas. There are no cell-cell interactions between these round-shaped cells. They contain huge numbers of vacuoles, filled with mucins, which are secreted from the cells. The mechanism behind this phenotype has recently begun to be elucidated. In highly differentiated adenocarcinomas the ErbB2/ErbB3 complex is activated, which is followed by phosphatidylinositol 3-kinase (PI3K) activation. p38 MAP kinase is activated downstream of PI3K and adherens junctions are disrupted via Rac1 activation. Loss of adherens junctions leads to the disappearance of tight junctions, which results in a loss of cell-cell interactions. Secretion of mucin is enhanced by activation of PI3K. One of the mucins - Muc4 - can activate ErbB2. Under normal conditions Muc4 and ErbB2 are separated by adherens and tight junctions, however in signet ring cells they are able to interact, since these junctions have been lost. Therefore, an activation loop is formed, consisting of ERbB2/ErbB3-Muc4-ErbB2/ErbB3. As a result, the ErbB2/ErbB3 signaling pathway becomes constitutively activated, cell-cell interactions are lost, and signet ring carcinomas are formed. As a result of constitutive activation of the ErbB2/ErbB3 complex, cell growth is continuously enhanced. Some signet ring cell carcinomas have been found to have mutations in the E-cadherin gene, which fits the above hypothesis.

MUC1 and maltose‑binding protein recombinant fusion protein combined with Bacillus Calmette‑Guerin induces MUC1‑specific and nonspecific anti‑tumor immunity in mice

Human mucin 1 (MUC1) is a target for immunotherapy. The major problem associated with MUC1‑based cancer vaccines is the weakness of the immunogenicity of MUC1. The present study aimed to develop an efficient cancer vaccine through generating a recombinant fusion protein consisting of MUC1 and maltose‑binding protein (MBP) by inserting seven tandem repeats encoding the human MUC1 gene into the pMAL‑c2 expression vector. Bacillus Calmette‑Guerin (BCG) was used as an adjuvant. MUC1 was found to predominantly induce T helper type 2 (Th2) cell responses. MUC1/BCG and MUC1‑MBP were found to generate T helper (Th) type 1 and 2 responses, while MUC1‑MBP/BCG induced a Th1 immune profile and stimulated MUC1‑specific cytotoxic T lymphocyte killing activity. MUC1‑MBP, as well as MBP and BCG alone were found to induce natural killer (NK) cell activity, with MUC1‑MBP/BCG observed to synergistically induce NK cell activity. Furthermore, MUC1‑MBP/BCG significantly inhibited MUC1+ B16 cell growth in mice. These findings show that MBP augments the immunogenicity of MUC1 and that BCG enhances the efficacy of the MUC1‑MBP vaccine. Thus, MUC1‑MBP/BCG may have potential as a cancer vaccine for clinical application.

Role of epidermal growth factor receptor in acute and chronic kidney injury

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase. Its activation results in beneficial or detrimental consequences, depending on the particular setting. Earlier studies in the animal model of acute kidney injury showed that EGFR activation promotes renal tubular cell proliferation. Activation of EGFR by its exogenous ligands, like EGF, can enhance recovery of renal function and structure following acute kidney injury. However, recent studies indicated that EGFR activation also contributes to development and progression of renal diseases in animal models of obstructive nephropathy, diabetic nephropathy, hypertensive nephropathy, and glomerulonephritis through mechanisms involved in activation of renal interstitial fibroblasts, induction of tubular atrophy, overproduction of inflammatory factors, and/or promotion of glomerular and vascular injury. This review highlights the actions and mechanisms of EGFR in a variety of acute and chronic kidney injuries.

Molecular targeted therapies in advanced gastric cancer: does tumor histology matter?

It is increasingly recognized that gastric cancer is a heterogeneous disease which may be divided into subgroups based on histological, anatomical, epidemiological and molecular classifications. Distinct molecular drivers and tumor biology, and thus different treatment targets and predictive biomarkers, may be implicated in each subtype. However, there is little evidence in the literature regarding the correlation among these different classifications, and particularly the molecular aberrations present in each subtype. In this review, we approach advanced gastric cancer (AGC) by presenting aberrant molecular pathways and their potential therapeutic targets in gastric cancer according to histological and anatomical classification, dividing gastric cancer into proximal nondiffuse, distal nondiffuse and diffuse disease. Several pathways are involved predominantly, although not exclusively, in different subtypes. This may help to explain the disappointing results of many published AGC trials in which study populations were heterogeneous regardless of clinicopathological characteristics of the primary tumor. Histological and anatomical classification may provide insights into tumor biology and facilitate selection of an enriched patient population for targeted agents in future studies and in the clinic. However, some molecular pathways implicated in gastric cancer have not been studied in correlation with histological or anatomical subtypes. Further studies are necessary to confirm the suggestion that such classification may predict tumor biology and facilitate selection of an enriched patient population for targeted agents in future studies and in the clinic.

Immunoregulatory protein profiles of necrotizing enterocolitis versus spontaneous intestinal perforation in preterm infants

Necrotizing enterocolitis (NEC) and spontaneous intestinal perforation (SIP) are the most common acute surgical emergencies associated with high morbidity and mortality in preterm infants. We aimed to compare the profiles of immunoregulatory proteins and identify novel mediators in plasma of NEC and SIP infants. We also investigated the expression of target genes in resected intestinal tissues and an enterocyte cell line. Using Cytokine Antibody Array assay, we reported the first comparative profiles of immunoregulatory proteins in plasma of NEC and SIP infants, and showed that dysregulated proteins belonged to functionally diversified categories, including pro- and anti-inflammation, angiogenesis, cell growth, wound healing, anti-apoptosis, cell adhesion and extracellular matrix reorganization. Validation by ELISA confirmed significantly higher concentrations of interleukin (IL)-6, angiopoietin (Ang)-2, soluble type II interleukin-1 receptor (sIL-1RII), and soluble urokinase-type plasminogen activator receptor (suPAR) in NEC infants compared with gestational age-matched control, and a lower level of an epidermal growth factor receptor, secreted form of receptor tyrosine-protein kinase ErbB3 (sErbB3), compared with SIP infants. mRNA expressions of IL1-RII and uPAR were up-regulated in resected bowel tissues from NEC infants, indicating that immunoregulation also occurred at the cellular level. In FHs-74 Int cells, Ang-2, IL1-RII and uPAR mRNA expressions were significantly induced by the combined treatment with lipopolysaccharide (LPS) and platelet activating factor (PAF). Our study provided plasmatic signatures of immunoregulatory proteins in NEC and SIP infants, and demonstrated involvement of multiple functional pathways. The magnitude of changes in these proteins was significantly more extensive in NEC infants, reflecting the different nature of injury and/or severity of inflammation. We speculate that dysregulation of IL-6, Ang-2, IL-1RII and uPAR occurred at both systemic and cellular levels, and probably mediated via LPS and endogeneous PAF signals. Such exaggerated immunologic responses may account for the high morbidity and mortality in NEC compared with SIP patients.

Heregulin β-1 induces loss of cell-cell contact and enhances expression of MUC1 at the cell surface in HCC2998 and MKN45-1 cells

Signal transduction and cell responses after stimulation with heregulin β-1 (HRG) are examined in HCC2998 and MKN45-1 cells, which have been used for a model system to study the formation of signet ring carcinomas, one of poorly differentiated adenocarcinomas. HRG stimulation causes rounding of the cells, responding to HRG. The adherens junction, which is present in the control cells, is disrupted and cell-cell interaction is lost after stimulation. Inhibition of phosphatidylinositol (PI)-3 kinase or p38 MAP kinase blocked this reaction, which indicates that the PI-3 kinase-p38 MAP kinase pathway is required for this reaction. Inhibition of the p38 MAP kinase pathway resulted in immediate restoration of cell-cell interaction. This result indicates that signaling for adherent molecules is strictly regulated by growth factor signaling. Expression of MUC1 at the cell surface is also observed and found to be expressed only after HRG stimulation. The total amount of MUC1 remains unchanged, suggesting that this amount is not due to induction of gene expression but to translocation of MUC1 from the inner membrane to the plasma membrane. This reaction is independent of the cytohesin pathway but dependent on PI-3 kinase activity. In addition to these reactions, HRG stimulates cell growth of both HCC2998 and MKN45-1 cells, depending on the ERK pathway given that the MEK inhibitor abolishes this effect. Therefore, HRG induces various reactions in HCC2998 and MKN45-1 cells by different pathways. These reactions are all related to characteristics of tumors, which implicates that HRG signaling can contribute to the formation of tumors.

EGF and TGF-β1 Effects on Thyroid Function

Normal epithelial thyroid cells in culture are inhibited by TGF-β1. Instead, transformed thyroid cell lines are frequently resistant to its growth inhibitory effect. Loss of TGF-β responsiveness could be due to a reduced expression of TGF-β receptors, as shown in transformed rat thyroid cell lines and in human thyroid tumors, or to alterations of other genes controlling TGF-β signal transduction pathway. However, in thyroid neoplasia, a complex pattern of alterations occurring during transformation and progression has been identified. Functionally, TGF-β1 acts as a tumor suppressor in the early stage of transformation or as a tumor promoter in advanced cancer. This peculiar pleiotropic behaviour of TGF-β may result from cross-talk with signalling pathways mediated by other growth factors, among which EGF-like ligands play an important role. This paper reports evidences on TGF-β1 and EGF systems in thyroid tumors and on the cross-talk between these growth factors in thyroid cancer.

Comparative study on overexpression of HER2/neu and HER3 in gastric cancer

BACKGROUND

Owing to the special importance of the HER family in tumorigenesis, the downstream signaling pathways and effectors have become the key molecules in the strategy of carcinoma-targeted therapy. Recent evidence that HER3 is responsible for tumor resistance to therapeutic agents targeting EGFR or HER2/neu, along with the new findings that HER3 is involved in the process of dedifferentiation of gastric cancer (GC) have highlighted the critical role of HER3 in cancer research. HER3 is becoming a new targeted molecule in cancer treatment. Here, we comparatively investigated the expression of HER2/neu and HER3 in gastric cancer of two pathologic types (intestinal type and diffuse type) using immunohistochemistry (IHC) and analyzed the correlation between overexpression of HER2 and HER3 and clinicopathologic parameters.

METHODS

An IHC study for HER2 and HER3 was performed on 102 formalin-fixed, paraffin-embedded specimens of GC-60 intestinal and 42 diffuse types. The correlation between overexpression of HER2 and HER3 and clinicopathologic parameters was statistically analyzed.

RESULTS

In the GC group, overexpression of HER2 and HER3 was detected in 19 (18.6%) and 14 (13.7%) of 102 GC patients, respectively. In a nontumorous group of 102 specimens, 5 were HER2-positive (4.9%) (18.6% vs. 4.9%, p < 0.01), and 2 were HER3-positive (2.0%) (13.7% vs. 2.0%, p < 0.01). No co-overexpression of HER2 and HER3 was observed. The intestinal type of GC exhibited a higher rate of HER2 overexpression than did the diffuse type (26.7% vs. 7.1%, p < 0.05), whereas the diffuse type of GC exhibited a significantly higher rate of HER3 overexpression than did the intestinal type (26.2% vs. 5.0%, p < 0.01). The overexpression rates of HER2 and HER3 in phase III-IV (TNM stage) disease were significantly higher than that in phase I-II disease (24.0% vs. 7.7%, p < 0.05 and 22.0% vs. 5.8%, p < 0.05, respectively). HER2 and HER3 overexpression was also correlated with a significantly worse survival (p = 0.046 and 0.024, respectively).

CONCLUSIONS

The selective overexpression of HER2 and HER3 in the two histologic types of gastric cancer is strongly associated with a poor prognosis. Being an important member of the HER family, HER3 may become another candidate for molecular-targeted therapy in gastric cancer, especially for the diffuse histologic type.

Tumor-specific apoptosis caused by deletion of the ERBB3 pseudo-kinase in mouse intestinal epithelium

Pharmacologic blockade of EGFR or the closely related receptor ERBB2 has modest efficacy against colorectal cancers in the clinic. Although the upregulation of ERBB3, a pseudo-kinase member of the EGFR/ERBB family, is known to contribute to EGFR inhibitor resistance in other cancers, its functions in normal and malignant intestinal epithelium have not been defined. We have shown here that the intestinal epithelium of mice with intestine-specific genetic ablation of Erbb3 exhibits no cytological abnormalities but does exhibit loss of expression of ERBB4 and sensitivity to intestinal damage. By contrast, intestine-specific Erbb3 ablation resulted in almost complete absence of intestinal tumors in the ApcMin mouse model of colon cancer. Unlike nontransformed epithelium lacking ERBB3, intestinal tumors lacking ERBB3 had reduced PI3K/AKT signaling, which led to attenuation of tumorigenesis via a tumor-specific increase in caspase-3-mediated apoptosis. Consistent with the mouse data, which suggest that ERBB3-ERBB4 heterodimers contribute to colon cancer survival, experimentally induced loss of ERBB3 in a KRAS mutant human colon cancer cell line was associated with loss of ERBB4 expression, and siRNA knockdown of either ERBB3 or ERBB4 resulted in elevated levels of apoptosis. These results indicate that the ERBB3 pseudo-kinase has essential roles in supporting intestinal tumorigenesis and suggest that ERBB3 may be a promising target for the treatment of colorectal cancers.

Is there an association between uterine leiomyomas and acid phosphatase locus 1 polymorphism?

OBJECTIVE

Platelet derived growth factor (PDGF) is involved in the development of leiomyomas. The low-molecular-weight phosphoprotein-tyrosine-phosphatase (LMWPTP), controlled by the highly polymorphic acid phosphatase locus 1 (ACP1), is able to dephosphorylate the PDGF receptor. Therefore, we searched for a possible association between ACP1 and leiomyomas.

STUDY DESIGN

We studied 172 women hospitalized for symptomatic leiomyomas requiring surgical intervention and 164 healthy women without clinical evidence of leiomyomas from the same white population. The chi(2) test of independence, Pearson correlation, analysis of variance, and post hoc test for difference between means were performed.

RESULTS

The distribution of ACP1 genotypes among patients does not differ significantly from that of healthy women. However, leiomyoma size was negatively correlated with ACP1 F isoform concentrations. Leiomyoma size was smaller among carriers of the *B/*B genotype, which has the highest concentration of the F isoform, than among carriers of *A/*A, *C/*B, and *C/*C genotypes, which have the lowest concentration of the F isoform.

CONCLUSION

High ACP1 F isoform concentration, through dephosphorylation of the PDGF receptor, may negatively regulate cell proliferation and growth of leiomyomas.

ERBBs in the gastrointestinal tract: recent progress and new perspectives

The gastrointestinal epithelium does much more than provide a physical barrier between the intestinal lumen and our internal milieu. It is actively engaged in absorption and secretion of salt and water via ion transporters, exchangers and selective ion channels. It is also a continuously self-renewing epithelium that undergoes ordered growth and differentiation along its vertical axis. From this dual perspective, we will consider the actions of the ERBB family of ligands and receptors in the maintenance of gastrointestinal homeostasis and discuss instances when the actions of this family go awry such as in cancer and Ménétrier's disease.

ErbB receptors and cell polarity: new pathways and paradigms for understanding cell migration and invasion

The ErbB family of receptor tyrosine kinases is involved in initiation and progression of a number of human cancers, and receptor activation or overexpression correlates with poor patient survival. Research over the past two decades has elucidated the molecular mechanisms underlying ErbB-induced tumorigenesis, which has resulted in the development of effective targeted therapies. ErbB-induced signal transduction cascades regulate a wide variety of cell processes, including cell proliferation, apoptosis, cell polarity, migration and invasion. Within tumors, disruption of these core processes, through cooperative oncogenic lesions, results in aggressive, metastatic disease. This review will focus on the ErbB signaling networks that regulate migration and invasion and identify a potential role for cell polarity pathways during cancer progression.

The ERBB3 receptor in cancer and cancer gene therapy

ERBB3, a member of the epidermal growth factor receptor (EGFR) family, is unique in that its tyrosine kinase domain is functionally defective. It is activated by neuregulins, by other ERBB and nonERBB receptors as well as by other kinases, and by novel mechanisms. Downstream it interacts prominently with the phosphoinositol 3-kinase/AKT survival/mitogenic pathway, but also with GRB, SHC, SRC, ABL, rasGAP, SYK and the transcription regulator EBP1. There are likely important but poorly understood roles for nuclear localization and for secreted isoforms. Studies of ERBB3 expression in primary cancers and of its mechanistic contributions in cultured cells have implicated it, with varying degrees of certainty, with causation or sustenance of cancers of the breast, ovary, prostate, certain brain cells, retina, melanocytes, colon, pancreas, stomach, oral cavity and lung. Recent results link high ERBB3 activity with escape from therapy targeting other ERBBs in lung and breast cancers. Thus a wide and centrally important role for ERBB3 in cancer is becoming increasingly apparent. Several approaches for targeting ERBB3 in cancers have been tested or proposed. Small inhibitory RNA (siRNA) to ERBB3 or AKT is showing promise as a therapeutic approach to treatment of lung adenocarcinoma.

Pathophysiological role of the activation of p38 mitogen-activated protein kinases in poorly differentiated gastric cancer

p38 mitogen-activated protein kinases (MAPK) contribute to the loss of cell-cell contact and the round cell shape characteristic of poorly differentiated gastric cancer. In the present study it is demonstrated that phospho-p38 MAPK level significantly increased in poorly differentiated gastric cancers in comparison to differentiated cancers and normal gastric mucosa by immunohistochemistry. Next, the pathophysiological roles of p38 MAPK activation were investigated in differentiated gastric cancer cell lines MKN7 and MKN28 and poorly differentiated gastric cancer cell lines KATO-III and MKN45 cells by incubating with specific p38 inhibitor SB203580 or inactivating analog SB202474. The distribution of F-actin on phalloidin staining was identified as fine cytoskeletal filaments in MKN7 and MKN28, but as dense membranous accumulation in KATO-III and MKN45 cells. The treatment with SB203580 but not SB202474 reduced irregular accumulation of F-actin in KATO-III and MKN45 cells. The expression of E-cadherin, ZO-1, occludin and claudin 4 was higher in MKN7 and MKN28 than KATO-III and MKN45 cells. The expression of E-cadherin in KATO-III cells was increased following treatment with SB203580, suggesting the suppression of E-cadherin at the transcriptional level independent of its genetic alterations. Thus, p38 MAPK signaling might contribute to the acquisition of malignant properties in poorly differentiated phenotypes.

Metastasis: the seed and soil theory gains identity

The metastatic spread of tumor cells to distant sites represents the major cause of cancer-related deaths. Cancer metastasis involves a series of complex interactions between tumor cells and microenvironment that influence its biological effectiveness and facilitate tumor cell arrest to distant organs. More than a century since Paget developed the theory of seed and soil, the enigma of tissue specificity observed in metastatic colonization of tumor cells begins to unfold itself. The advent of new technologies has led to the discovery of novel molecules and pathways that confer metastasis-associated properties to the cancer cells, mediating organ specificity and unique genetic signatures have been developed using microarray studies. Future clinical studies and new antimetastatic compounds aiming to improve survival of patients with metastasis will most probably be based on these signatures. This review summarizes the plethora of old and new molecules that are strongly correlated with organ-specific metastases and which provide now an identity to the theory of seed and soil.

Pleckstrin-2 selectively interacts with phosphatidylinositol 3-kinase lipid products and regulates actin organization and cell spreading

Pleckstrin-2 (PLEK2) has been implicated to be regulated by phosphatidylinositol (PI) 3-kinase, while pleckstrin1 (PLEK1) has been suggested to be a major PKC substrate in platelets. In this paper, we confirmed that PLEK2 specifically bound to the PI 3-kinase products in vitro and explored its behavior. PLEK2 was found to be expressed in various adherent cell lines, while PLEK1 expression was restricted to non-adherent cells in the protein level. Expression of PLEK2 in COS1 cells induced formation of protrusive F-actin structure and enhanced the actin rearrangements induced on collagen- or fibronectin-coated plates. A PLEK2 mutant incapable of binding to the PI 3-kinase products did not show any effect on actin rearrangement. Knockdown of PLEK2 by shRNA inhibited spreading of HCC2998 adenocarcinoma cells. PLEK2 colocalized with Rac and was suggested to be oligomerized. These results suggest that PLEK2 is involved in actin rearrangement in a PI 3-kinase dependent manner.

Expression of MUC1 in primary and metastatic human epithelial ovarian cancer and its therapeutic significance

BACKGROUND

MUC1 is associated with cellular transformation and tumorigenicity and is considered as an important tumor-associated antigen (TAA) for cancer therapy. The objective of this study was to evaluate the patterns of MUC1 expression in primary tumors and metastatic lesions in the advanced stages of epithelial ovarian cancers (EOCs) and correlate the expression with clinicopathological features.

METHODS

The expression of MUC1 was examined on frozen tissue sections from primary EOC (n=42), the matched metastatic lesions (n=30) and paraffin-embedded tissue sections from primary EOC (n=60), normal ovarian tissues (n=20) using immunohistochemistry (IHC) by monoclonal antibody (MAb) C595.

RESULTS

The expression of MUC1 was found in 92% (39/42) of EOC and 90% (27/30) of the matched metastatic lesions in frozen tissue sections respectively while the expression of MUC1 was found in 95% (57/60) of EOC and 5% (1/20) of normal ovarian tissues in paraffin-embedded sections respectively. Most of the tumors showed moderate to strong intensity staining while normal ovarian tissues only showed weak intensity staining. The overexpression of MUC1 was significantly associated with various progression parameters such as tumor stage, grade, residual disease status and presence of ascites (P<0.05).

CONCLUSIONS

MUC1 is overexpressed in above 90% of late stage of EOC and of metastatic lesions but not in normal ovarian tissues, and the high expression of MUC1 is correlated with EOC progression. MUC1 antigen may be a useful therapeutic target to prevent the development of incurable, recurrent metastatic EOC.

Muc4 is required for activation of ErbB2 in signet ring carcinoma cell lines

Signet-ring cell carcinoma is one of the most malignant tumors, classified histologically as a poorly differentiated adenocarcinoma. The ErbB2/ErbB3 complex is often constitutively activated, which suggests that the ErbB2/ErbB3 signaling pathway may be important for malignancy of this tumor. However, the mechanism underlying this activation has not been understood. Here, we show that ErbB2 and Muc4 bind in signet ring carcinoma cells, which was not seen in highly differentiated adenocarcinoma cell lines. ErbB3 was suggested to be a substrate of ErbB2 because knockdown of ErbB2 resulted in less phosphorylation of ErbB3. Inhibition of expression of Muc4 at the cell surface by the treatment of the cells with benzyl-GalNac, an inhibitor of mucin secretion, blocked phosphorylation of ErbB3, suggesting that activity of ErbB2 depends on the expression of Muc4. These results supply the biochemical backgrounds in recent studies suggesting the contribution of Muc4 in the tumorigenesis.

Expression and nuclear localization of ErbB3 in prostate cancer

PURPOSE

The ErbB1 and ErbB2 receptors have been implicated in prostate cancer progression, but less is known about the role and biology of other ErbB receptor family members in prostate cancer. The aim of this study was to analyze the expression and localization of ErbB3 in prostate tissues and prostate cancer cell lines.

EXPERIMENTAL DESIGN

Immunohistochemistry of ErbB3 was done on prostate cancer tissue sections from 143 patients and on a tissue microarray containing 390 cores of radical prostatectomy-derived specimens representing normal, prostatic intraepithelial neoplasia, and malignant tissues from 81 patients. ErbB3 subcellular localization was studied by Western blot analysis in LNCaP, 22Rv1, PC-3, and DU145 prostate cancer cell lines.

RESULTS

Immunohistochemistry analysis of prostate cancer tissues revealed that >90% of prostate cancer tissues displayed cytoplasmic ErbB3 staining. Minimal ErbB3 nuclear staining was observed in normal prostate tissues and benign prostatic hyperplasia tissues; in contrast, ErbB3 was frequently localized in the nucleus of cancerous tissues. This nuclear localization was more frequent (P < 0.001) in hormone-refractory tissues (17 of 17, 100%) compared with hormone-sensitive samples (37 of 92, 40.2%). Additionally, in the tissue microarray, increased nuclear ErbB3 was associated with increasing Gleason grade. Interestingly, Western blot analysis of cytoplasmic and nuclear subcellular fractions showed that ErbB3 nuclear localization was more prevalent in hormone-sensitive prostate cancer cell lines (LNCaP and 22Rv1) compared with hormone-insensitive cell lines (PC-3 and DU145).

CONCLUSIONS

ErbB3 nuclear localization discriminates normal from malignant prostate tissues and between tumors from hormone-sensitive versus hormone-refractory prostate cancer. ErbB3 nuclear staining seems to be associated with risk of disease progression. The high frequency of ErbB3 nuclear localization in hormone-refractory tissues indicates that ErbB3 warrants further study to understand its association with prostate cancer disease progression.

Mutation of the PI3' kinase gene in a human colon carcinoma cell line, HCC2998

HCC2998 is a highly differentiated human colon carcinoma cell line, which has been shown to be converted to a poorly differentiated one after expression of a constitutively active phosphatidylinositol 3-kinase (PI3' kinase). These cells express aberrant sizes of a regulatory subunit of PI3' kinase, p85alpha, with molecular weights of 50 and 76 kDa at a very low level. To elucidate how these cells express these proteins, we analyzed mutations within the p85alpha gene. DNA sequencing analysis revealed that these mutant proteins were generated by independent point mutations in the two alleles of the p85alpha gene: one in the coding sequence, and the other in the acceptor sequence for splicing. Introduction of wild-type p85alpha into HCC2998 cells induced slight rounding of the cells and enhancement of mucin secretion. At the same time, a membrane receptor, ErbB3, was phosphorylated on tyrosine, which in turn, binds to PI3' kinase. Since ErbB3 is upstream of PI3' kinase, it is likely that there is an autocrine loop in which PI3' kinase is activated by ErbB3, which may contribute to dedifferentiation of the cells.

Common cancer biomarkers

There is an increasing interest in complementing conventional histopathologic evaluation with molecular tools that could increase the sensitivity and specificity of cancer staging for diagnostic and prognostic purposes. This study strove to identify cancer-specific markers for the molecular detection of a broad range of cancer types. We used 373 archival samples inclusive of normal tissues of various lineages and benign or malignant tumors (predominantly colon, melanoma, ovarian, and esophageal cancers). All samples were processed identically and cohybridized with an identical reference RNA source to a custom-made cDNA array platform. The database was split into training (n = 201) and comparable prediction (n = 172) sets. Leave-one-out cross-validation and gene pairing analysis identified putative cancer biomarkers overexpressed by malignant lesions independent of tissue of derivation. In particular, seven gene pairs were identified with high predictive power (87%) in segregating malignant from benign lesions. Receiver operator characteristic curves based on the same genes could segregate malignant from benign tissues with 94% accuracy. The relevance of this study rests on the identification of a restricted number of biomarkers ubiquitously expressed by cancers of distinct histology. This has not been done before. These biomarkers could be used broadly to increase the sensitivity and accuracy of cancer staging and early detection of locoregional or systemic recurrence. Their selective expression by cancerous compared with paired normal tissues suggests an association with the oncogenic process resulting in stable expression during disease progression when the presently used differentiation markers are unreliable.

A novel snake venom vascular endothelial growth factor (VEGF) predominantly induces vascular permeability through preferential signaling via VEGF receptor-1

Vascular endothelial growth factor (VEGF)/vascular permeability factor induces both angiogenesis and vascular permeability mainly through VEGF receptor (VEGFR)-2 activation. VEGF binds VEGFR-1 as well, but the importance of VEGFR-1 signaling in vascular permeability has been largely neglected. Here, we report the purification and characterization of a novel VEGF-like protein from Trimeresurus flavoviridis Habu snake venom. The Habu snake has a venom-specific VEGF-like molecule, T. flavoviridis snake venom VEGF (TfsvVEGF), in addition to VEGF-A. TfsvVEGF has almost 10-fold less mitotic activity than VEGF(165), a predominant isoform of human VEGF-A, but a similar effect on vascular permeability. TfsvVEGF bound VEGFR-1 and induced its autophosphorylation to almost the same extent as VEGF(165), but bound VEGFR-2 weakly and induced its autophosphorylation almost 10-fold less effectively than VEGF(165). This unique binding affinity for VEGFR-1 and VEGFR-2 leads to the vascular permeability-dominant activity of TfsvVEGF. These results suggest that Habu snakes have acquired a highly purposive molecule for a toxin, which enhances the toxicity in envenomation without inducing effective angiogenesis and the following regeneration of damaged tissues, taking advantage of the difference in signaling properties involving VEGFR-1 and VEGFR-2 between vascular permeability and angiogenesis. TfsvVEGF is thus a potent inducing factor selective for vascular permeability through preferential signaling via VEGFR-1. These data strongly indicate the importance of VEGFR-1 signaling in vascular permeability.

The MUC1 oncoprotein activates the anti-apoptotic phosphoinositide 3-kinase/Akt and Bcl-xL pathways in rat 3Y1 fibroblasts

The MUC1 transmembrane glycoprotein is overexpressed by most human carcinomas. Overexpression of MUC1 confers transformation; however, the signaling pathways activated by this oncoprotein are largely unknown. The present studies demonstrated that MUC1-induced transformation of 3Y1 fibroblasts is associated with increased levels of phospho-Akt and phospho-Bad. The finding that LY294002 blocks MUC1-mediated increases in phospho-Akt and phospho-Bad supports the involvement of phosphoinositide 3-kinase (PI3K) as an upstream effector of this response. We also show that MUC1 increases the expression of the anti-apoptotic Bcl-x(L) protein (but not Bcl-2) by a PI3K-independent mechanism. In concert with these results, MUC1 attenuated (i) the loss of mitochondrial transmembrane potential, (ii) mitochondrial cytochrome c release, (iii) activation of caspase-9, and (iv) induction of apoptosis by the antimetabolite, 1-beta-d-arabinofuranosylcytosine. Similar results were obtained with the anti-cancer agent, gemcitabine. These findings indicate that expression of MUC1 in 3Y1 cells activates the anti-apoptotic PI3K/Akt and Bcl-x(L) pathways.

The PI 3-kinase-Rac-p38 MAP kinase pathway is involved in the formation of signet-ring cell carcinoma

Signet-ring cell carcinoma is classified in poorly differentiated adenocarcinoma with an aggressive nature and a poor prognosis. We have shown that the activation of PI 3-kinase in highly differentiated adenocarcinomas induces loss of cell-cell contact and formation of vacuoles, giving phenotypes similar to those of signet-ring cell lines. SB203580, a potent p38 MAP kinase inhibitor, blocked this transition, and expression of an active form of MKK6 (MKK6DA), an activator of p38 MAP kinase, gave effects similar to those induced by expression of the active form of PI 3-kinase (BD110), although formation of large vacuoles was not induced. Activation of MKK3, another activator of p38 MAP kinase, was activated in native signet-ring carcinoma cell lines. Anchorage-independent growth of signet-ring cell lines was inhibited by LY294002 or SB203580. These results suggest that p38 MAP kinase is functioning downstream of PI 3-kinase in signaling of the malignant phenotype. Secretion of mucins was enhanced in BD110-expressing cells, but not in MKK6DA-expressing cells, suggesting that secretion of mucins is independent of the MKK6-p38 MAP kinase cascade. Thus, there may be at least two pathways, p38 MAP kinase-dependent and -independent, which are involved in regulation of cell-cell contact and the protein secretion system, respectively.