| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |





From the Department of Pathology,* Stanford University School of Medicine, Stanford, California; the Department of Urology,
Stanford University School of Medicine, Stanford, California; the Department of Urology,
Santa Clara Valley Medical Center, San Jose, California; the Department of Urology,
Palo Alto VA Hospital, Palo Alto, California; the Department of Surgery,¶ Urological Research Centre, University of Western Australia, Perth, Western Australia, Australia; and the Department of Genetics,|| Stanford University School of Medicine, Stanford, California
| Abstract |
|---|
|
|
|---|
Each histological variant of renal cell carcinoma shows distinct karyotypic abnormalities including loss of chromosome 3p in clear cell carcinomas10 and trisomy of chromosomes 7, 12, 16, 17, and 20 in papillary carcinomas.11 These molecular genetic alterations have been coupled with histological features to form a revised classification of renal cell tumors.12 Since changes in gene copy number (gene amplification, aneuploidy, and allelic loss) as well as differences in histological appearance have been associated with altered gene expression patterns, we anticipated that each of the histological subtypes of renal cell carcinoma would have unique and easily identifiable gene expression signatures. In addition, an analysis of seven renal cell carcinomas by Young et al13 suggested that gene expression profiles could be associated with histological subtype.
To further test whether gene expression patterns can add to the classification of renal cell carcinomas, we performed DNA microarray analysis on 41 renal tumors of diverse histological types and on three normal kidney samples using 22,648 element-spotted DNA microarrays representing 17,083 different human genes. We report that gene expression patterns can readily distinguish between the histological subtypes of renal cell carcinoma and that conventional renal cell carcinomas with predominantly granular cytoplasm may represent a heterogeneous group distinct from conventional clear cell carcinoma. Our data set is a potential rich source for novel markers of the subtypes of renal cell carcinoma and may offer unique biological insights into these tumors.
| Materials and Methods |
|---|
|
|
|---|
Samples were obtained from fresh nephrectomy specimens and immediately frozen on dry ice. Paraffin sections from each specimen were reviewed by a single pathologist (J.P.T.H.) and classified according to Union International Contre le Cancer (UICC) and American Joint Committee on Cancer (AJCC) criteria14 and can be reviewed at http://genome-www.stanford.edu/renal_cell_carcinoma/. Our series included 28 conventional renal cell carcinomas (three of which had accompanying renal vein tumor thrombi), four papillary carcinomas, three chromophobe carcinomas, two oncocytomas, and one angiomyolipoma. The conventional carcinomas were subdivided into 23 clear cell and five granular cell carcinomas based on whether they contained cytoplasmic granules in the majority of the tumor cells. Three normal kidney samples were obtained fromareas of the nephrectomy specimens uninvolved by carcinoma.
Microarray Analysis
Methods for mRNA extraction, hybridization to 17,083 gene (represented by 22,648 cDNAs) DNA microarrays, and interpretation of data have been described elsewhere15-18 and detailed protocols are available at http://cmgm.Stanford.EDU/pbrown/. Each tumor mRNA was hybridized against a common reference pool of mRNA made from 11 different cell lines as we have described previously.17
Average linkage hierarchical cluster analysis was used to organize gene expression data. Expression levels for each transcript were centered across all samples. We selected transcripts whose expression level differed by a factor of four or greater from the normalized mean level of expression in at least two of the samples. We further restricted our analysis to those genes with a fluorescent hybridization signal greater than 100 over background in 80% of the experimental samples. Of the initial list of 22,648 cDNAs, 1550 cDNAs met these criteria.
The significance analysis of microarrays (SAM) procedure was used to identify genes significantly associated with the conventional granular cell carcinoma subtype.19 SAM computes a two-sample T-statistic for the normalized log ratios of the gene expression levels for each gene. It thresholds the T-statistics to produce a "significant" gene list and provides an estimate of the false discovery rate (genes that differ between samples by chance alone) from randomly permuted data. SAM also allows identification of genes associated with classes of tumors that may not be evident by hierarchical clustering analysis.
Immunohistochemistry
Paraffin blocks were available from 30 of the 38 cases. Four-µm sections were cut and immunohistochemistry was performed using monoclonal antibodies for CK7 (clone OV-TL 12/30, BioGenex, San Ramon, CA; 1:200), CD10 (clone 56C6, Novocastra, Newcastle-on-Tyne, UK; 1:50), and vimentin (clone V9, BioGenex; ready to use) according to previously published protocols.20
| Results |
|---|
|
|
|---|
|
Inspection of the genes that characterize each of the histological subtypes of renal cell carcinoma offers some insights into the biology of these tumors. A group of 230 transcripts was overexpressed in all conventional carcinomas with clear cytoplasm, most of which are unnamed or poorly characterized (Figure 1)
. VEGF, the glucose transporters 1 and 3 (SLC2A1 and SLC2A3),21
endothelin-1,22,23
and insulin-like growth factor binding protein 323
were all expressed at high levels in the clear cell carcinomas and are all primarily regulated by the HIF-1 transcription factor. Normally, HIF-1 levels are regulated by the von Hippel-Lindau (VHL) protein, which targets HIF-1 protein for ubiquitylation-mediated degradation.24
The VHL gene is inactivated in most conventional clear cell carcinomas, and HIF-1 protein is expressed at high levels. In our data set, neither VHL nor HIF-1 transcript levels varied across the tumor samples. Since the VHL gene is usually inactivated by loss of one allele and mutation of the second, and HIF-1 levels are regulated post-translationally, it is not surprising that neither gene shows altered transcript levels. Interestingly, HIF2-
(EPAS1) was highly expressed in the clear cell carcinomas. Although less well characterized than HIF1-
, EPAS1 is thought to be regulated by VHL,25
and our data suggests it may be regulated transcriptionally. Collagen types I, III, IV, V, and VI, lysyl oxidase, heparan sulfate proteoglycan 2, and fibronectin may be expressed by cells in the interstitium, while PECAM1 (CD31), EPAS1, VEGF receptor 2, and cadherin 5 are known to be expressed in endothelial cells and probably reflect the rich vascularity of these tumors.
Genes overexpressed in papillary carcinoma consist of two distinct clusters of 15 and 44 genes (Figure 1)
. These genes include cytokeratin subsets that appear to be uniquely overexpressed in these tumors and could be exploited diagnostically. Papillary carcinomas also express high levels of
-methylacyl-CoA racemase (AMACR), a gene found to be overexpressed in prostate cancer by DNA microarray analysis.26,27
The oncogenes GRO 1 and GRO 2 are also expressed at high levels in these tumors, although it is unclear whether they are expressed by the malignant cells or by the characteristic foamy macrophages that line the papillae in these tumors. Additionally, other transcripts, such as osteoprotegerin and I factor, are known to be expressed by macrophages.
Chromophobe carcinomas and oncocytomas both show increased expression of the stem cell factor receptor (KIT, CD117), a gene not previously implicated in these neoplasms (Figure 1)
. This gene is also highly expressed in gastrointestinal stromal sarcoma (GIST) by immunohistochemistry28
and by DNA microarray analysis29
and is a potential therapeutic target.30
Several genes that are highly expressed in oncocytomas and chromophobe carcinomas, including nicotinamide nucleotide transhydrogenase, fumarate hydratase, and solute carrier family 25 members 4&5, encode mitochondrial proteins. Oncocytomas are known to be rich in mitochondria,31
and chromophobe carcinomas contain abundant microvesicles that likely represent altered mitochondria.32,33
The gene expression profiles of conventional carcinomas with granular cytoplasm are distinct from those with clear cytoplasm and appeared heterogeneous. Since their expression patterns over the 1550 transcripts were highly diverse and shared similarities with the other histological subtypes of renal malignancies, we were not able to identify a discrete set of genes that characterize these malignancies using hierarchical clustering analysis. We used the SAM procedure to compare the gene expression patterns of the conventional granular renal carcinomas to the other renal tumors in our data set to identify genes that characterize the granular cell phenotype. Although SAM analysis identified 91 transcripts highly expressed in the granular cell carcinomas and two expressed at significantly lower levels compared to the other tumors, none of these 93 transcripts showed consistent expression changes across all of the conventional carcinomas with granular cytoplasm, nor did they reliably distinguish these tumors from other histological subtypes (data not shown).
To evaluate whether the transcripts we identified could help distinguish between tumor subtypes, we selected commercially available antibodies for three proteins whose transcripts were differentially expressed (keratin 7, CD10, and vimentin) and performed immunohistochemical analysis of paraffin-embedded tissues from the set of tumors that were analyzed by DNA microarray (Table 1)
. In each case, the protein expression pattern usually reflected the RNA expression pattern observed in the DNA microarray analysis (Figure 2)
. Most notably, vimentin readily distinguished between the clear cell carcinoma and chromophobe carcinoma subtypes, a distinction that may be difficult on hematoxylin and eosin-stained sections. Thus, these data sets represent a potential source of immunohistochemical markers that may aid in distinguishing renal tumor subclasses.
|
|
| Discussion |
|---|
|
|
|---|
We were surprised that conventional renal cell carcinomas with granular cytoplasm are molecularly distinct from typical conventional carcinomas with clear cytoplasm. Before standardization of renal tumor pathology by the Heidelberg classification and the Union International Contre le Cancer, many tumors designated as granular cell were actually oncocytomas, papillary carcinomas, chromophobe carcinomas, and other rare variants.12,14 Now, only those tumors with granular cytoplasm that fail to meet criteria for any of these diagnoses are classified with clear cell carcinomas as "conventional carcinomas" because of their similar clinical behavior. Some investigators have even suggested that clear cell and granular carcinomas are variants of a single histological and molecular subclass. However, our data suggest that the histological differences between clear and granular cell carcinoma correlate with distinct differences in gene expression patterns. Perhaps more surprising, the conventional carcinomas with granular cytoplasm display significant heterogeneity in their gene expression profiles and do not appear to represent a single tumor subtype. This heterogeneity will need to be confirmed by analysis of additional tumors; however, if true, it could signal differences in the biology of these tumors and may help in identifying tumors that respond differently to therapy.
Despite their distinctive appearance histologically, oncocytomas and chromophobe carcinomas had highly similar patterns of gene expression. In part, this similarity may be due to the small number of these tumors we analyzed or the set of transcripts we used in our analysis. However, this similarity also could reflect their common histogenesis from the distal renal tubule, or similar biological behavior since both tumors are often clinically indolent.36,37 One intriguing possibility is that these tumors arise from a common molecular genetic lesion and therefore display similar gene expression profiles. Individuals affected with the Birt-Hogg-Dubé syndrome develop multifocal chromophobe carcinomas and oncocytomas, often within the same kidney, suggesting these tumors may arise from a common genetic alteration.38 Transcriptional profiling of additional chromophobe carcinomas and oncocytomas will be necessary to shed light on the molecular genetic similarities and differences between these tumors.
Two groups, using techniques similar to ours, have analyzed gene expression profiles of renal cell carcinoma, and reported expression profiles similar to ours. Young et al13 analyzed seven renal carcinomas on DNA microarrays with 7075 genes and identified 32 transcripts overexpressed and 48 transcripts underexpressed in conventional compared to chromophobe renal cell carcinoma (RCC) and an oncocytoma. Forty-eight of these 80 genes were well measured in our tumors and all but three showed expression patterns identical to their report. Takahashi et al39 identified 32 transcripts with increased expression and 77 with decreased expression in clear cell carcinoma relative to normal kidney. Eighty-five of the 89 transcripts represented in our data set showed patterns of expression identical to that seen in their clear cell cancers.39 Using high-density DNA arrays spotted on nylon membranes, Boer et al40 described 1738 transcripts differentially expressed between normal and cancerous renal tissues. Tumors were not characterized by histological subtype, making comparison with our results difficult. However, 123 transcripts (representing 89 unique Unigene clusters) were differentially expressed between conventional and chromophobe carcinomas. Of the 64 that were well measured on our microarrays, 53 showed expression patterns that matched those reported by Boer et al.40 Therefore, microarray analysis of gene expression appears to be robust and reproducible despite the use of different tumor sets and measurement on different array platforms.
Expression patterns associated with papillary and granular cell carcinomas have not been described. Our data set, therefore, may serve as a rich source of molecular markers that aid in the discrimination of renal cell carcinoma subtypes. The very good correlation of keratin 7, CD10, and vimentin mRNA expression noted on microarray with protein expression seen by immunohistochemistry highlights the potential of cDNA microarray technology to identify novel diagnostic antibodies that could be used clinically.
Microarray analysis of malignancies from other organ sites has revealed molecular subtypes of tumors that are histologically indistinguishable and discrete gene expression profiles have been identified that correlate with clinical outcomes.16,17,34,35,41-44 Takahashi et al39 identified 51 genes with expression patterns that correlated with adverse outcome in 29 patients followed 10 years after resection of their clear cell carcinoma. When we performed hierarchical clustering analysis of the conventional clear cell carcinomas in our data set using 45 of their 51 genes that were present on our arrays, the tumors were sorted into two groups with expression patterns similar to those reported (data not shown). Additional clinical follow-up of patients in our series will be necessary to determine whether the expression patterns observed for this set of genes or additional sets of genes carry prognostic information.
Global analysis of gene expression using cDNA microarray technology offers significant opportunities to identify novel markers that discriminate between classes of renal tumors and holds promise in identifying molecular subclasses of tumors with differing prognosis. These data provide a starting point for identification of proteins with altered expression in renal cell carcinomas. Such proteins may be measurable in the serum or urine and could serve as new markers for this disease. They could be used clinically to monitor response to therapy or, possibly, to screen those at high risk for renal cell carcinoma such as individuals with hereditary forms of the disease. Ultimately, biological insights gleaned from microarray analysis of gene expression in renal cell carcinomas may provide new targets for immune or biological therapies.
| Acknowledgements |
|---|
| Footnotes |
|---|
Supported by National Institutes of Health grants CA85129 and CA84967, the Kidney Cancer Association Eugene P. Schonfeld Award, and the Howard Hughes Medical Institute.
John P.T. Higgins and Rajesh Shinghal contributed equally to this work.
Accepted for publication December 9, 2002.
| References |
|---|
|
|
|---|
. Genes Dev 1998, 12:149-162
and insulin-like growth factor 2. Cancer Res 1999, 59:3915-3918
-Methylacyl-CoA racemase: a new molecular marker for prostate cancer. Cancer Res 2002, 62:2220-2226
-Methylacyl coenzyme A racemase as a tissue biomarker for prostate cancer. JAMA 2002, 287:1662-1670This article has been cited by other articles:
![]() |
I. G. Yulug and B. Gur-Dedeoglu Functional genomics in translational cancer research: focus on breast cancer Brief Funct Genomic Proteomic, March 7, 2008; (2008) eln009v1. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. G. Leong, K. Niessen, I. Kulic, A. Raouf, C. Eaves, I. Pollet, and A. Karsan Jagged1-mediated Notch activation induces epithelial-to-mesenchymal transition through Slug-induced repression of E-cadherin J. Exp. Med., November 26, 2007; 204(12): 2935 - 2948. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Jones and T. A. Libermann Genomics of Renal Cell Cancer: The Biology Behind and the Therapy Ahead Clin. Cancer Res., January 15, 2007; 13(2): 685s - 692s. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. S. Tompkins, J. Hagen, A. A. Frazier, T. Lushnikova, M. P. Fitzgerald, A. di Tommaso, V. Ladeveze, F. E. Domann, C. M. Eischen, and D. E. Quelle A Novel Nuclear Interactor of ARF and MDM2 (NIAM) That Maintains Chromosomal Stability J. Biol. Chem., January 12, 2007; 282(2): 1322 - 1333. [Abstract] [Full Text] [PDF] |
||||
![]() |
K.-i. Shioi, A. Komiya, K. Hattori, Y. Huang, F. Sano, T. Murakami, N. Nakaigawa, T. Kishida, Y. Kubota, Y. Nagashima, et al. Vascular Cell Adhesion Molecule 1 Predicts Cancer-Free Survival in Clear Cell Renal Carcinoma Patients Clin. Cancer Res., December 15, 2006; 12(24): 7339 - 7346. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Rohan, J. J. Tu, J. Kao, P. Mukherjee, F. Campagne, X. K. Zhou, E. Hyjek, M. A. Alonso, and Y.-T. Chen Gene Expression Profiling Separates Chromophobe Renal Cell Carcinoma from Oncocytoma and Identifies Vesicular Transport and Cell Junction Proteins as Differentially Expressed Genes Clin. Cancer Res., December 1, 2006; 12(23): 6937 - 6945. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. Hotakainen, S. Lintula, B. Ljungberg, P. Finne, A. Paju, U.-H. Stenman, and J. Stenman Expression Of Human Chorionic Gonadotropin {beta}-Subunit Type I Genes Predicts Adverse Outcome In Renal Cell Carcinoma J. Mol. Diagn., November 1, 2006; 8(5): 598 - 603. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y.-T. Chen, J. J. Tu, J. Kao, X. K. Zhou, and M. Mazumdar Messenger RNA Expression Ratios among Four Genes Predict Subtypes of Renal Cell Carcinoma and Distinguish Oncocytoma from Carcinoma Clin. Cancer Res., September 15, 2005; 11(18): 6558 - 6566. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Jones, H. Otu, D. Spentzos, S. Kolia, M. Inan, W. D. Beecken, C. Fellbaum, X. Gu, M. Joseph, A. J. Pantuck, et al. Gene Signatures of Progression and Metastasis in Renal Cell Cancer Clin. Cancer Res., August 15, 2005; 11(16): 5730 - 5739. [Abstract] [Full Text] [PDF] |
||||
![]() |
X. J. Yang, M.-H. Tan, H. L. Kim, J. A. Ditlev, M. W. Betten, C. E. Png, E. J. Kort, K. Futami, K. A. Furge, M. Takahashi, et al. A Molecular Classification of Papillary Renal Cell Carcinoma Cancer Res., July 1, 2005; 65(13): 5628 - 5637. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Togashi, T. Katagiri, S. Ashida, T. Fujioka, O. Maruyama, Y. Wakumoto, Y. Sakamoto, M. Fujime, Y. Kawachi, T. Shuin, et al. Hypoxia-Inducible Protein 2 (HIG2), a Novel Diagnostic Marker for Renal Cell Carcinoma and Potential Target for Molecular Therapy Cancer Res., June 1, 2005; 65(11): 4817 - 4826. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. N. Schuetz, Q. Yin-Goen, M. B. Amin, C. S. Moreno, C. Cohen, C. D. Hornsby, W. L. Yang, J. A. Petros, M. M. Issa, J. G. Pattaras, et al. Molecular Classification of Renal Tumors by Gene Expression Profiling J. Mol. Diagn., May 1, 2005; 7(2): 206 - 218. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Sultmann, A. v. Heydebreck, W. Huber, R. Kuner, A. Buness, M. Vogt, B. Gunawan, M. Vingron, L. Fuzesi, and A. Poustka Gene Expression in Kidney Cancer Is Associated with Cytogenetic Abnormalities, Metastasis Formation, and Patient Survival Clin. Cancer Res., January 15, 2005; 11(2): 646 - 655. [Abstract] [Full Text] [PDF] |
||||
![]() |
M.-H. Tan, C. G. Rogers, J. T. Cooper, J. A. Ditlev, T. J. Maatman, X. Yang, K. A. Furge, and B. T. Teh Gene Expression Profiling of Renal Cell Carcinoma Clin. Cancer Res., September 15, 2004; 10(18): 6315S - 6321S. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Volinia, R. Evangelisti, F. Francioso, D. Arcelli, M. Carella, and P. Gasparini GOAL: automated Gene Ontology analysis of expression profiles Nucleic Acids Res., July 1, 2004; 32(suppl_2): W492 - W499. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. R. Rhodes, J. Yu, K. Shanker, N. Deshpande, R. Varambally, D. Ghosh, T. Barrette, A. Pandey, and A. M. Chinnaiyan Large-scale meta-analysis of cancer microarray data identifies common transcriptional profiles of neoplastic transformation and progression PNAS, June 22, 2004; 101(25): 9309 - 9314. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. A. Furge, K. A. Lucas, M. Takahashi, J. Sugimura, E. J. Kort, H.-o. Kanayama, S. Kagawa, P. Hoekstra, J. Curry, X. J. Yang, et al. Robust Classification of Renal Cell Carcinoma Based on Gene Expression Data and Predicted Cytogenetic Profiles Cancer Res., June 15, 2004; 64(12): 4117 - 4121. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. P.T. Higgins, L. Wang, N. Kambham, K. Montgomery, V. Mason, S. U. Vogelmann, K. V. Lemley, P. O. Brown, J. D. Brooks, and M. van de Rijn Gene Expression in the Normal Adult Human Kidney Assessed by Complementary DNA Microarray Mol. Biol. Cell, February 1, 2004; 15(2): 649 - 656. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. K. Cashion, C. J. Driscoll, and O. Sabek Emerging Genetic Technologies in Clinical and Research Settings Biol Res Nurs, January 1, 2004; 5(3): 159 - 167. [Abstract] [PDF] |
||||
![]() |
A. Tsuchiya, M. Sakamoto, J. Yasuda, M. Chuma, T. Ohta, M. Ohki, T. Yasugi, Y. Taketani, and S. Hirohashi Expression Profiling in Ovarian Clear Cell Carcinoma: Identification of Hepatocyte Nuclear Factor-1{beta} as a Molecular Marker and a Possible Molecular Target for Therapy of Ovarian Clear Cell Carcinoma Am. J. Pathol., December 1, 2003; 163(6): 2503 - 2512. [Abstract] [Full Text] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |