Immunodetection of c-met-oncogene's protein product in renal cell neoplasia

The expression pattern of Von Hippel-Lindau tumor suppressor protein, MET proto-oncogene, and TFE3 transcription factor oncoprotein in renal cell carcinoma in Upper Egypt

BACKGROUND

Genetic alterations in renal cell carcinoma (RCC) involve tumor suppressor genes such as Von Hippel-Lindau (VHL); proto-oncogenes such as MET and transcription factors such as TFE3 oncoprotein.

AIM

To examine the clinicopathologic features and the expression of some oncogenic molecules in various RCCs in patients from Upper Egypt.

MATERIALS AND METHODS

The authors examined the expression pattern of pVHL; MET; and TFE3 proteins in 59 RCC using immunoperoxidase staining methods. The study group consisted of clear cell RCCs (CRCC); papillary RCCs type 1 (PRCC1); papillary RCCs type 2 (PRCC2); Xp11-2 translocation RCCs (XP11.2RCC); chromophobe RCCs (ChRCC); and sarcomatoid RCCs (SRCC).

RESULTS

Variations were found in the expression of these molecules in the different types of RCCs. The mean age of RCCs among Egyptians was 52.70 ± 1.73 years; with male sex predominance. Mass lesion; pain; and hematuria were the main presenting features. Metastatic disease was more frequent with CRCC variant. pVHL expression was strong in PCRCC2; Xp11.2RCC; and ChRCC; moderate in CRCC; and weak in both PRCC1 and sarcomatoid RCC. MET protein expression was moderate in Xp11.2RCC; PRCC1; PRCC2; and sarcomatoid RCC. TFE3 protein expression was strong in Xp11.2RCC and PRCC2 variants. The expression was moderate in PRCC1; CRCC; ChRCC; and sarcomatoid RCC. Positive correlation was found in the expression of the different proteins (pVHL; MET; and TFE3) and some histological features (tumor grade; inflammation; necrosis and metastasis) and the presence of metastasis and some histological features (inflammation and/or necrosis).

CONCLUSIONS

This study provides the first indication about the clinicopathologic features of RCCs in Upper Egypt. The variable expression of these molecules in the different variants of RCC suggests that several oncogenic pathways are operational in their development.

Origin of renal cell carcinomas

Cancer is a heritable disorder of somatic cells: environment and heredity are both important in the carcinogenic process. The primal force is the "two hits" of Knudson's hypothesis, which has proved true for many tumours, including renal cell carcinoma. Knudson et al. [1, 2] recognised that familial forms of cancer might hold the key to the identification of important regulatory elements known as tumour-suppressor genes. Their observations (i.e., that retinoblastoma tend to be multifocal in familial cases and unifocal in sporadic presentation) led them to propose a two-hit theory of carcinogenesis. Furthermore, Knudson postulated that patients with the familial form of the cancer would be born with one mutant allele and that all cells in that organ or tissue would be at risk, accounting for early onset and the multifocal nature of the disease. In contrast, sporadic tumours would develop only if a mutation occurred in both alleles within the same cell, and, as each event would be expected to occur with low frequency, most tumours would develop late in life and in a unifocal manner [3, 4]. The kidney is affected in a variety of inherited cancer syndromes. For most of them, both the oncogene/tumour-suppressor gene involved and the respective germline mutations have been identified. Each of the inherited syndromes predisposes to distinct types of renal carcinoma. Families with hereditary predisposition to cancer continue to provide a unique opportunity for the identification and characterisation of genes involved in carcinogenesis. A surprising number of genetic syndromes predispose to the development of renal cell carcinoma, and genes associated with five of these syndromes have been already identified: VHL, MET, FH, BHD and HRPT2. Few cancers have as many different types of genetic predisposition as renal cancer, although to date only a small proportion of renal cell cancers can be explained by genetic predisposition.

Presence of phosphorylated hepatocyte growth factor receptor/c-Met is associated with tumor progression and survival in patients with conventional renal cell carcinoma

PURPOSE

Hepatocyte growth factor receptor (HGFR/c-Met) signaling is associated with tumor progression in various cancers. The clinical significance and pathologic roles of phosphorylated HGFR/c-Met in renal cell carcinoma (RCC) are not fully understood; therefore, this study sought to clarify the possible role of two tyrosine residues (pY1234/pY1235 and pY1349) in HGFR/c-Met.

EXPERIMENTAL DESIGN

The kinetics of tyrosine phosphorylation at these two residues was examined in a human renal carcinoma cell line, ACHN cells. In addition, phosphorylated HGFR/c-Met expression (using phosphorylation site-specific antibodies for pY1234/pY1235 and pY1349) was examined in 114 tumor sections of conventional RCC patients by immunohistochemistry. The relationships between these expressions and clinicopathologic features and survival were also investigated.

RESULTS

Although phosphorylation of Y1349 HGFR/c-Met was observed for 120 minutes after HGF treatment of ACHN cells, maximal phosphorylation of Y1234/Y1235 was observed at 30 minutes followed by a rapid inactivation. Median rates (range) of cancer cells immunopositive for pY1234/pY1235 HGFR/c-Met and pY1349 HGFR/c-Met in the tumor sections were 0% (0-5.2%) and 14.3% (0-64.3%), respectively. Positive expression of pY1349 HGFR/c-Met was significantly associated with high pT stage, presence of metastasis, and high-grade carcinoma. Multivariate Cox analysis revealed that the positive expression of pY1349 HGFR/c-Met was a significant and an independent predictor of cause-specific survival (odds ratio, 2.94; 95% confidence interval, 1.12-7.72; P = 0.028).

CONCLUSIONS

Phosphorylated HGFR/c-Met may be important in the tumor progression of RCC. Expression of pY1349 HGFR/c-Met is a useful predictor for metastasis and survival of conventional RCC patients.

Levels of angiogenesis and expression of angiogenesis-related genes are prognostic for organ-specific metastasis of renal cell carcinoma

BACKGROUND

To identify organ-specific, metastasis-related factors that can be used to predict the development and location of metastasis of clear cell renal cell carcinoma (CRCC), the authors assessed the angiogenesis and the expression of angiogenesis-related genes in primary and metastatic tumors.

METHODS

They evaluated intratumoral microvessel density (MVD) by immunohistochemical staining, assessed the expression of angiogenesis-related genes by mRNA in situ hybridization, and determined the clinicopathologic characteristics of 92 archival specimens of primary and metastatic CRCCs from 54 patients. All 38 metastatic tumor specimens were resected from 24 patients.

RESULTS

The pathologic stage (P=0.026) of the primary tumor specimen was an important predictor for metastasis, as were MVD (P=0.000025) and the ratio of matrix metalloproteinases (MMPs) to E-cadherin (M/E ratio; P=0.000041). In addition, primary tumor specimens resected from patients with metastatic CRCCs had high MVD, high levels of MMP-2 expression, and a high M/E ratio (P <0.05). Relative to the primary tumors, the metastatic tumors also had high MVD, overexpression of basic fibroblast growth factor, vascular endothelial growth factor, interleukin-8, MMPs, and a high M/E ratio (P <0.05). Multivariate analysis revealed that MVD and the M/E ratio in the primary tumor were independent prognostic factors for metastasis (P=0.049 and P=0.001, respectively). Furthermore, the M/E ratio in metastatic tumor specimens resected from the lung and lymph node was an independent prognostic factor for metastasis (P=0.01823 and P=0.03950, respectively).

CONCLUSIONS

The current study indicated that angiogenesis and M/E ratio were specific predictors for metastases of RCC, especially to the lung or lymph node. Therefore, MMPs and E-cadherin could be relevant targets for novel therapeutic strategies to control or prevent the metastasis of RCC.

c-Met as a target for human cancer and characterization of inhibitors for therapeutic intervention

Receptor tyrosine kinase (RTK) targeted agents such as trastuzumab, imatinib, bevacizumab, and gefitinib inhibitors have illustrated the utility of targeting this protein class for treatment of selected cancers. A unique member of the RTK family, c-Met, also represents an intriguing target for cancer therapy that is yet to be explored in a clinical setting. The proto-oncogene, c-Met, encodes the high-affinity receptor for hepatocyte growth factor (HGF) or scatter factor (SF). c-Met and HGF are each required for normal mammalian development and have been shown to be particularly important in cell migration, morphogenic differentiation, and organization of three-dimensional tubular structures (e.g. renal tubular cells, gland formation, etc.) as well as cell growth and angiogenesis. Both c-Met and HGF have been shown to be deregulated in and to correlate with poor prognosis in a number of major human cancers. New data describing the constitutive phosphorylation of c-Met in a number of human tumors is presented here along with a variety of mechanisms by which c-Met can become activated, including mutation and gene amplification. In support of the clinical data implicating c-Met activation in the pathogenesis of human cancers, introduction of c-Met and HGF (or mutant c-Met) into cells conferred the properties of motility, invasiveness, and tumorgenicity to the transformed cells. Conversely, the inhibition of c-Met with a variety of receptor antagonists inhibited the motility, invasiveness, and tumorgenicity of human tumor cell lines. Consistent with this observation, small-molecule inhibitors of c-Met were developed that antagonized c-Met/HGF-dependent phenotypes and tumor growth in mouse models. This review will address the potential for development of c-Met inhibitors for treatment of human cancers with particular emphasis on recent findings with small-molecule inhibitors.

Overexpression of KIT in chromophobe renal cell carcinoma

We analysed gene-expression profiles in 15 surgical specimens of conventional, papillary, and chromophobe renal cell carcinomas (RCCs) using high-density oligonucleotide arrays. From about 12,000 genes targeted by the array, 67 were upregulated specifically in each histological type of RCC. The oncogene KIT was one of the genes whose expression was upregulated specifically in chromophobe RCCs. Immunohistochemical analysis demonstrated the KIT gene product on the cell membrane of chromophobe RCC in all cases, although it was not detected in conventional RCCs or non-neoplastic kidneys except for weak staining in the cytoplasm of renal tubules. These results suggest that each histological subtype of RCC has a unique gene-expression profile, and in particular indicates for the first time that KIT could be a useful marker for chromophobe RCC. As overexpression of KIT might be involved in tumor growth, KIT could be a new therapeutic target in this special type of RCC.

Increase in hepatocyte growth factor receptor tyrosine kinase activity in renal carcinoma cells is associated with increased motility partly through phosphoinositide 3-kinase activation

Dysregulated cell motility is one of the major characteristics of invasion and metastatic potentials of malignant tumor cells. Here, we examined the hepatocyte growth factor (HGF)-induced cell motility of two human renal carcinoma cell lines, ACHN and VMRC-RCW. Scattering and migration was induced in ACHN in an HGF-dependent manner, whereas they were maintained in VMRC-RCW even in the absence of HGF. In VMRC-RCW, HGF receptor (HGFR) tyrosine kinase was constitutively active, and sequence analysis showed N375S, A1209G and V1290L mutations. However, transfection experiments using porcine aortic endothelial (PAE) cells demonstrated that no single mutation or combination of two or three mutations caused HGF-independent constitutive activation. Conversely, the expressed amount of receptor protein had a pivotal role in the basal kinase activity. With respect to downstream signaling molecules of HGFR in ACHN or VMRC-RCW, the Ras-MAPK pathway was downregulated, whereas phosphoinositide 3-kinase (PI3-kinase) was not further activated by HGF-treatment in VMRC-RCW cells. The PI3-kinase inhibitors, wortmannin and LY294002 strongly inhibited spontaneous migration of VMRC-RCW. One transfected PAE cell line with massive overexpression of HGFR demonstrated scattered morphology and increased PI3-kinase activity in association with increased motility, which was partially inhibited by LY294002. Taken together, our results indicate that the overexpression of HGFR causes increase in cellular motility and PI3-kinase shows the important contribution on the increased motility of renal carcinoma cells.

c-met tyrosine kinase receptor expression is associated with abnormal beta-catenin expression and favourable prognostic factors in invasive breast carcinoma

AIMS

Receptor-type tyrosine kinases are important in cell signal transduction and proliferation. Abnormal expression of tyrosine kinases often leads to malignant transformation. c-met is a tyrosine kinase receptor and its ligand is hepatocyte growth factor (HGF). In this study, we have evaluated c-met expression in 69 invasive breast carcinomas and statistically analysed this expression with known clinicopathological prognostic parameters and patients' survival. We also studied for the first time c-met expression in association with E-cadherin and beta-catenin expression.

METHODS AND RESULTS

Immunohistochemistry (ABC-HRP method) was peformed for the detection of c-met, E-cadherin and beta-catenin. c-met immunoreactivity was observed in 58% of cases and was associated with the lobular type of breast carcinomas (P = 0.012), low histological grade ductal carcinomas (P = 0.05), favourable prognostic and predictive factors such as oestrogen and progesterone receptor immunohistochemical expression and negative c-erbB-2 expression (P = 0.05, P = 0.014 and P = 0.03, respectively). c-met immunoreactivity did not correlate with lymph node status, tumour size and stage of the disease. Cox's proportional hazard regression model demonstrated that tumours with positive c-met immunoreactivity correlated significantly with favourable patients' survival (P = 0.028). When c-met staining was compared with E-cadherin and beta-catenin expression, a statistical significant correlation was established between c-met immunoreactivity and abnormal beta-catenin expression (P = 0.025) suggesting possible involvement of c-met in the downregulation of the E-cadherin-catenin complex, possibly through tyrosine phosphorylation of beta-catenin.

CONCLUSION

c-met immunohistochemical expression seems to be associated with abnormal beta-catenin expression, good prognostic and predictive factors and favourable outcome in breast cancer patients.