Molecular genetic investigation of sporadic renal cell carcinoma: analysis of allele loss on chromosomes 3p, 5q, 11p, 17 and 22.

To investigate the role of tumour-suppressor genes on the short arm of chromosome 3 in the mechanism of tumorigenesis in non-familial renal cell carcinoma, we analysed 55 paired blood-tumour DNA samples for allele loss on chromosome 3p and in the region of known or putative tumour-suppressor genes on chromosomes 5, 11, 17 and 22. Sixty-four per cent (35/55) of informative tumours showed loss of heterozygosity (LOH) of at least one locus on the short arm of chromosome 3, compared with only 13% at the p53 tumour-suppressor gene and 6% at 17q21. LOH at chromosome 5q21 and 22q was uncommon (2-3%). Detailed analysis of the regions of LOH on chromosome 3p suggested that, in addition to the VHL gene in chromosome 3p25-p26, mutations in one or more tumour-suppressor genes in chromosome 3p13-p24 may be involved in the pathogenesis of sporadic renal cell carcinoma (RCC). We also confirmed previous suggestions that chromosome 3p allele loss is not a feature of papillary RCC (P < 0.05).     

Comparative analysis of loss of heterozygosity of specific chromosome 3, 13, 17, and X loci and TP53 mutations in human epithelial ovarian cancer

We previously reported the identification of three minimal regions of deletion on the short arm of chromosome 3 (3p) in epithelial ovarian tumor specimens, suggesting that the inactivation of tumor-suppressor genes in these regions may be important in terms of ovarian tumorigenesis. Another previous study of ovarian cancer observed that allele loss of chromosome 179 was frequently found in ovarian tumors that also showed loss of heterozygosity (LOH) of chromosomes 3p, 13q, 17p, and Xp. In an independent study, we also reported a high frequency of LOH for selected chromosome 17 loci in high-grade and late-stage ovarian tumors. We have extended our LOH analysis of chromosome 3p to include 102 ovarian tumor specimens (29 and 73 samples were previously examined for LOH of chromosome 3p and 17 markers, respectively), using additional polymorphic markers, to assess the coordinate LOH of loci representing the three chromosome 3p minimal regions of deletions [von Hippel-Lindau syndrome (VHL), thyroid hormone receptor beta, and fragile histidine triad (FHIT)] and LOH of other important loci [tumor protein 53 (TP53), breast cancer 1 early onset (BRCA1), breast cancer 2 early onset, retinoblastoma 1, ornithine carbamoyltransferase, and androgen receptor] or somatic mutations in TP53. There was a significant association between LOH of any chromosome 3p marker and LOH of any chromosome 17 marker (P = 0.026). The frequency of LOH at the TP53 locus was higher in the group of samples that displayed LOH of a 3p marker (P = 0.019), as was the frequency of LOH at the BRCA1 locus (P = 0.014). LOH of chromosome 3p was noted in four specimens that did not display LOH of either the BRCA1 or the TP53 locus, indicating that LOH of these loci need not precede LOH of the chromosome 3p loci. We found a significant association between LOH of the VHL (3p25) locus and LOH of any chromosome 17 marker (P = 0.005), suggesting that there may be an important relationship, in the tumorigenesis of epithelial ovarian cancer, between a gene at 3p25 and a gene located on chromosome 17. Our results indicate that inactivation of p53 by somatic mutation is unlikely to be a prerequisite to chromosome 3p LOH, because we found no significant association between mutations in TP53 and LOH of the three chromosome 3p loci. The frequency of LOH at the FHIT locus at 3p14 increased significantly with advancing age at diagnosis (P = 0.018), as did the frequency of somatic TP53 mutations (P = 0.008).     

Microsatellite analysis reveals deletion of a large region at chromosome 8p in conventional renal cell carcinoma

Loss of heterozygosity (LOH) at chromosome 8p is associated with the progression of conventional (non‐papillary) renal cell carcinomas (RCC). To determine the tumor suppressor gene locus, we carried out a deletion mapping of chromosome 8p at 10 microsatellite loci in 96 RCCs. LOH occurred in 32% of the tumors. The smallest overlapping region of deletion at chromosome 8p11.2–p23.1 corresponds to approximately 34‐cM genetic distance. No small interstitial deletion was seen. Int. J. Cancer 80:22–24, 1999. © 1999 Wiley‐Liss, Inc.     

Deletion of chromosome 3p14.2-p25 involving the VHL and FHIT genes in conventional renal cell carcinoma

Loss of heterozygosity (LOH) at chromosome 3p and inactivation of the VHL gene are associated with the development of conventional renal cell carcinomas (RCCs). Recently, it was suggested that LOH at the FHIT gene at 3p14.2 is an early event in the development of RCC and is characteristic for all types of RCC. We have analyzed 88 conventional, 30 papillary, and 22 chromophobe RCCs for LOH at the VHL and FHIT regions and at other loci on chromosome 3p. A continuous deletion of 3p14.2-p25 harboring the VHL and FHIT genes occurred in 96% of the conventional RCCs but only in 10% of the papillary RCCs and 18% of the chromophobe RCCs. Our data indicate that LOH at chromosome 3p14.2-p25 is specific for conventional RCC and that loss of one allele of both the VHL and FHIT genes occurs in early stage of tumorigenesis.     

Loss of two new loci on chromosome 8 (8p23 and 8q12-13) in human prostate cancer

Inactivation of tumor suppressor genes due to allelic loss is thought to be an important mechanism of gene alterations in prostatic carcinogenesis. Loss of sequences on the short arm of chromosome 8 (8p) has been reported in human cancers, especially of 8p22 and 8p12-21 in prostate cancer. By using PCR analysis of polymorphic microsatellite repeat markers at four 8p loci and three 8q loci in 60 tumors, we observed deletion of sequences at two other deletion domains (8p23, and 8q12-13). There was loss in 51 of 60 cases (85%) with at least one marker. Four distinct regions of loss detected were: i) at 8p23, at locus D8S262; ii) at 8p22, on locus D8S259; iii) at 8p12, on loci D8S255 and D8S285; iv) at 8q12-13, on loci between D8S260 and D8S528. We found that 29% of the tumors showed LOH at 8p23; 19% LOH on 8p22; 54% had LOH at 8p12; and 48% had LOH at 8q12-13. There was higher frequency of LOH at 3 or more loci in samples of T3 stage (62%) as compared to T2 stage (13.3%) which suggests higher incidence of LOH in advanced stage of prostate cancer. We report deletion of two novel loci at 8p23 and 8q12-13, these regions may contain putative tumor suppressor genes in prostate cancer.     

Detailed genetic and physical mapping of tumor suppressor loci on chromosome 3p in ovarian cancer.

Hemizygosity and homozygosity mapping studies show that many common sporadic cancers including lung, breast, kidney, cervical, ovarian, and head and neck cancer display deletions on the short arm of chromosome 3. For ovarian cancer, monochromosomal transfer suppression studies have identified three candidate regions for chromosome 3p ovarian cancer tumor suppressor genes (OCTSGs). To accurately map OCTSG candidate regions, we analyzed 70 ovarian tumors for loss of heterozygosity (LOH) at 20 loci on chromosome 3p that were selected to target those regions proposed to contain tumor suppressor genes for common sporadic cancers. All samples were informative for at least five markers. In 33 (52%) tumors without microsatellite instability, LOH was observed for at least one 3p marker. Analysis of 27 ovarian tumors demonstrating both loss and retention of 3p markers enabled us to define four nonoverlapping minimal deletion regions (OCLOHRs): (a) OCLOHR-1 mapped distal to D3S3591 at 3p25-26; (b) OCLOHR-2 mapped between D3S1317 and D3S1259 at 3p24-25; (c) OCLOHR-3 mapped between D3S1300 and D3S1284, an area that includes the FHIT locus at 3p14.2; and (d) OCLOHR-4 mapped between D3S1284 and D3S1274 at 3p12-13, a region known to contain overlapping homozygous deletions in lung and breast tumor cell lines. However, microsatellite markers from the chromosome 3p21.3 interval homozygously deleted in lung cancer cell lines did not identify a distinct OCLOHR. The frequency and extent of 3p LOH correlated with tumor stage such that LOH at two or more OCLOHRs was present in 53% (16 of 30) of stage III tumors but only 26% (5 of 19) of stage I/II tumors (P = 0.08). To determine the relationship between the OCLOHRs and the three candidate ovarian cancer suppression regions (OCSRs) identified previously by monochromosome transfer studies, we performed detailed genetic and physical mapping studies to define the extent of the three candidate OCSRs and to establish YAC contigs covering each region. OCSR-A at 3p25-26 and OCSR-B at 3p24 were shown to overlap with OCLOHR-1 and OCLOHR-2, respectively, providing further evidence for OCTSGs in these regions. We also show that OCSR-C overlaps with a locus at 3p21.3 previously implicated in lung and breast cancer.     

Cytogenetic and molecular findings in 75 clear cell renal cell carcinomas

Cytogenetic analysis of 75 clear cell renal cell carcinomas (RCC) from adult patients revealed abnormal karyotypes in 59 (79%) tumors. Among structural abnormalities, the most frequent were deletions and unbalanced translocations leading to loss of 3p (found in 68% of karyotypically abnormal tumors), followed by rearrangements of chromosomes 5 (in 37%) and 1 (in 20%). Fifteen unbalanced interchromosomal rearrangements and one reciprocal translocation have not been hitherto reported in clear cell RCC. The most common numerical aberrations were trisomy 7, seen in 44% of tumors, and loss of chromosome Y, detected in 48% of RCCs diagnosed in male patients. In 25 tumors, loss of heterozygosity (LOH) analysis was performed using five polymorphic markers spanning region 3p13-p25. LOH was identified in 10 RCCs with 3p loss detected cytogenetically and 4 karyotypically aberrant tumors without cytogenetic rearrangements of 3p; no LOH was found in 3 tumors with 3p loss seen at the cytogenetic level. Overall, 3p loss was detected by cytogenetic and/or LOH analyses in 75% of RCCs with abnormal karyotype studied. The presence or absence of 3p loss did not correlate with tumor size, nodal involvement, tumor grade or its ability to metastasize. However, karyotypes of metastasizing tumors contained more aberrations than those of non-metastasizing RCCs (5.5 versus 2.9 aberrations per tumor, respectively), and -14/14q-, -17 and -10 were significantly more frequent in metastasizing tumors, suggesting that these aberrations might contribute to the progression of RCC. One patient had t(X;1)(p11.2;p34) as a sole abnormality in the stemline. This is the sixth case with this translocation reported to date. Together with our case, all but 1 RCC with t(X;1)(p11.2;p34) had morphology with a clear cell component, which contrasts these RCCs from tumors harboring t(X;1)(p11.2;q21) that largely had papillary morphology.     

Elevated frequency of loss of heterozygosity in mammary tumors arising in mouse mammary tumor virus/neu transgenic mice.

Loss of heterozygosity (LOH) analysis was performed on 62 mammary tumors that were induced in (BALB/c x C57BL/6)F1 mouse mammary tumor virus/neu transgenic mice. Eighty-six simple sequence length polymorphism markers were used to cover all of the somatic chromosomes. Frequency of LOH was observed to be significant for chromosomes 4 (50%), 19 (32%), and 8 (21%). On chromosome 4, at least three distinct regions of allelic deletions could be identified: one proximal to 22 cM; the second close to the p16INK4a/p15INK4b locus, which is commonly deleted in various tumors; and the third one in the proximity of Mom1. The frequency of LOH on chromosome 19 was the same for the four markers used. Our data suggested the presence of two distinct LOH loci, one proximal to 47 cM and the other at the distal region. On chromosome 8, possibly two distinct LOH loci could be recognized, one around 52 cM and the other one at 67 cM or distal to it. These regions map close to E-cadherin (Cdh1) and M-cadherin (Cdh15) loci, respectively. Because LOH sites are thought to harbor tumor suppressor genes, this allelotype screening has allowed the mapping of putative tumor suppressor genes that may be implicated, in collaboration with the erbB-2/neu oncogene, in the development of mammary tumors in these transgenic mice.     

Deletion mapping on the short arm of chromosome 1 in Merkel cell carcinoma

Twenty-two Merkel cell carcinoma (MCC) biopsies and six cell lines from 24 patients were examined for loss of heterozygosity (LOH) at 11 loci on 1p and one on 1q, to determine LOH regions on chromosome 1p. Sixteen (73%) tumors had LOH for at least one locus; 14 demonstrated LOH at more than one locus, and 7 (29%) samples had more than one region of loss, with 4 of these having loss at all informative loci on 1p. Three common regions of loss (SRO) were defined by LOH in multiple tumors. Eight samples demonstrated LOH between D1S214 and D1S160 (1p36), seven between D1S234 and D1S186 (1p35), and 11 for the region centromeric of D1S211 and D1S220 (1p32-1p33). Seven samples (29%) demonstrated more than one region of loss. LOH on 1p occurs frequently in MCC and more than one tumor suppressor gene on 1p is likely to play a role in the development of this tumor type.     

Allelic loss on chromosome 17 in human ovarian cancer

In order to identify a common region of deletion on chromosome 17 potentially containing a tumor-suppressor gene, 27 ovarian carcinomas and 3 ovarian tumors of low malignant potential (LMP) were examined for loss of heterozygosity (LOH) at 6 p arm and 10 q arm loci. Ninety percent of all tumors had deletions at one or more loci. On the p arm, there was a single near-common region of deletion on 17p 13.3 (D/7S30/ pYNZ22.1; 86% LOH), an intervening locus with a low LOH rate, and a more proximal locus on 17p11.2 (D/7S58/pEW301; 82% LOH) with a high LOH rate. In less aggressive tumors, LOH at Df 7S30 was not accompanied by LOH at p53. The q arm had a common region of deletion for high-stage carcinoma at D/7S579 (Mfd 188; 74% LOH) on q21, a locus tightly linked to the familial breast-ovarian-cancer syndrome (BRCAI) locus. D/7S579 was lost in all informative high-stage carcinomas and retained in all low-stage carcinomas and tumors of LMP. There may be at least 2 tumor-suppressor genes, an early-acting gene on the p arm and a gene on the q arm involved in tumor progression and metastasis.     

The genetic locus NRC-1 within chromosome 3p12 mediates tumor suppression in renal cell carcinoma independently of histological type, tumor microenvironment, and VHL mutation

Human chromosome 3p cytogenetic abnormalities and loss of heterozygosity have been observed at high frequency in the nonpapillary form of sporadic renal cell carcinoma (RCC). The von Hippel-Lindau (VHL) gene has been identified as a tumor suppressor gene for RCC at 3p25, and functional studies as well as molecular genetic and cytogenetic analyses have suggested as many as two or three additional regions of 3p that could harbor tumor suppressor genes for sporadic RCC. We have previously functionally defined a novel genetic locus nonpapillary renal carcinoma-1 (NRC-1) within chromosome 3p12, distinct from the VHL gene, that mediates tumor suppression and rapid cell death of RCC cells in vivo. We now report the suppression of tumorigenicity of RCC cells in vivo after the transfer of a defined centric 3p fragment into different histological types of RCC. Results document the functional involvement of NRC-1 in not only different cell types of RCC (i.e., clear cell, mixed granular cell/clear cell, and sarcomatoid types) but also in papillary RCC, a less frequent histological type of RCC for which chromosome 3p LOH and genetic aberrations have only rarely been observed. We also report that the tumor suppression observed in functional genetic screens was independent of the microenvironment of the tumor, further supporting a role for NRC-1 as a more general mediator of in vivo growth control. Furthermore, this report demonstrates the first functional evidence for a VHL-independent pathway to tumorigenesis in the kidney via the genetic locus NRC-1.     

Distinct regions of frequent loss of heterozygosity of chromosome 5p and 5q in human esophageal cancer

Loss of heterozygosity (LOH) studies reported thus far suggest that tumor suppressor loci on chromosome 5q are important in esophageal cancer (EC) while little is known about the involvement of chromosome 5p. To investigate the potential existence of tumor suppressor gene(s) on chromosome 5 contributing to the development of EC, we performed LOH studies using a total of 24 polymorphic markers spanning the entire chromosome 5. Seventy primary esophageal cancers were microdissected and allelic deletions were detected by polymerase chain reaction (PCR)-single strand conformation polymorphism or by microsatellite analysis. LOH was observed in at least 1 of the loci in 47 of 70 (67%) esophageal tumors. Initially, 40 tumors [24 squamous cell carcinomas (SCC) and 16 adenocarcinomas (ADC)], each with matched histologically normal esophageal mucosa, were analyzed at 15 marker loci on 5p and 5q. A novel locus, D5S667 on 5p15.2, exhibited the highest frequency of LOH (44%) in these tumors along with another previously reported region of frequent deletion, irf-1 (5q31.1). In a series of 30 additional EC tumors (11 SCC and 19 ADC), a detailed LOH analysis of chromosome 5p15.2 region was conducted using 10 additional polymorphic markers, which mapped the frequently deleted region within 1 cM. Overall, LOH at the D5S667 locus was observed more frequently in SCC than in ADC (62% vs. 23%, p = 0.01). This significant rate of LOH of a distinct region of chromosome 5p implicates the existence of a putative tumor suppressor gene locus involved in EC. Int. J. Cancer 78:600–605, 1998. © 1998 Wiley-Liss, Inc.     

Allelic loss on chromosome 1 is associated with tumor progression of cervical carcinoma.

BACKGROUND: Alterations in chromosome 1 are common in human malignancies. The frequency of loss of heterozygosity (LOH) on chromosome 1 in cervical carcinoma and its clinical significance are not clearly understood. METHODS: LOH on chromosome 1 was studied in 100 cervical carcinomas by the polymerase chain reaction (PCR) using 29 highly polymorphic microsatellite markers spaced approximately 10 centimorgans apart. Loci with high frequencies of LOH were identified and the findings were correlated with clinicopathologic characteristics. RESULTS: LOH on chromosome 1 at 1 or more loci was detected in 93% of tumors. The frequencies of LOH at locus D1S2829 (1p31), D1S2663 (1p36.3), and D1S2725 (1q25) exceeded 30%, and 12 other loci exhibited frequencies of LOH of 20-30%. Advanced stage tumors had a significantly higher percentage of informative microsatellite markers with LOH than early stage tumors. Of the 29 microsatellite markers studied, 4 loci had a significantly higher frequency of LOH in Stage III and IV tumors than in earlier stage tumors. CONCLUSIONS: Frequent aberrations on chromosome 1 in cervical carcinoma suggest that inactivation of tumor suppressor genes is important in cervical tumorigenesis. Higher frequencies of LOH in Stage III and IV tumors suggest that chromosome 1 changes are late events in cervical carcinoma. The findings of this study are consistent with earlier reports that suggest that tumor suppressor genes are present at 1p36.3 and 1p31. To the authors' knowledge, the high frequency of LOH mapped to 1q25 has not been reported previously. Its significance awaits further clarification.     

Deletion of chromosome 11p15, p12, q22, q23-24 loci in human prostate cancer

Loss of heterozygosity (LOH) on chromosome 11 is frequently altered in various epithelial cancers. The present study was designed to investigate LOH on chromosome 11 in microdissected samples of normal prostatic epithelium and invasive carcinoma from the same patients. For this purpose, DNA was extracted from the microdissected normal and tumor cells of 38 prostate cancers, amplified by polymerase chain reaction PCR and analyzed for LOH on chromosome 11 using 9 different polymorphic DNA markers (D11S1307, D11S989, D11S1313, D11S898, D11S940, D11S1818, D11S924, D11S1336 and D11S912). LOH on chromosome 11 was identified in 30 of 38 cases (78%) with at least one marker. Four distinct regions of loss detected were: 1) at 11p15, at loci between D11S1307 and D11S989; 2) at 11p12, on locus D11S131 (11p12); 3) at 11q22, on loci D11S898, D11S940 and D11S1818; and 4) at 11q23-24, on loci between D11S1336 and D11S912. We found 25% of the tumors with LOH at 11p15; 39% had LOH at 11p12; 66% had LOH at 11q22; and 47% had LOH at 11q23-24. These deletions at 11p15, 11p12, 11q22 and 11q23-24 loci were not related to the stage or grade of the tumor. Int. J. Cancer 72:283–288, 1997. © 1997 Wiley-Liss, Inc.     

人卵巢癌3号染色体短臂杂合性丢失的研究

目的探讨3号染色体短臂(3p14)等位基因杂合性丢失(10ss 0f heterozygosity,LOH)与人卵巢癌发生及发展之间的相关性研究.方法采用聚合酶链反应并结合二核苷酸重复序列多态性方法,分别对31例卵巢癌及24例卵巢良性肿瘤患者的组织标本DNA中3p14上3个微卫星位点(D3S1234、D3S1300、D3S1312)杂合性丢失(LOH)进行检测,同时还随机地检测31例卵巢癌中21例患者的血清DNA中3p14的LOH.结果31例卵巢癌组织DNA中21例(67.7%)至少在1个微卫星位点中出现杂合性丢失,11例卵巢癌患者(35.5%)有2个以上微卫星位点出现LOH.癌组织DNA中基因杂合性丢失频率与癌细胞分化程度呈正相关,与肿瘤病理类型及FIGO分期无关.24例卵巢良性肿瘤组织及血清DNA中均未出现3p位点上的杂合性丢失.21例卵巢癌血清DNA与肿瘤组织DNA 3p14基因3个微卫星位点杂合性丢失率之间存在明显的相关性(P＜0 05).结论鉴于人卵巢癌3p14出现杂合性丢失率与其癌细胞分化恶性程度相关以及卵巢癌患者血清DNA与癌组织DNA中3p14出现LOH相一致,故本文实验结果提示3p14 LOH的检测可能具有对卵巢癌患者的临床诊断潜在性价值.     

Loss of heterozygosity of chromosome 3p21 is associated with mutant TP53 and better patient survival in non-small-cell lung cancer

Allelic loss of chromosome region 3p21.3 occurs early and frequently in non-small-cell lung cancer, and numerous tumor suppressor genes at this locus may be targets of inactivation. Using an incident case series study of non-small-cell lung cancer, we sought to determine the prevalence of loss of heterozygosity (LOH) in the 3p21.3 region and to examine the associations between this alteration and patient outcome, exposure to tobacco smoke, occupational asbestos exposure, and additional molecular alterations in these tumors. We examined LOH at 7 microsatellite markers in the chromosome 3p21.3 region, and LOH was present in at least one of the loci examined in 60% (156 of 258) of the tumors, with the prevalence of LOH at individual loci ranging from 15 to 56%. Occupational asbestos exposure and TP53 mutation were significantly associated with more extensive 3p21 LOH. In squamous cell carcinomas, measures of cumulative smoking dose were significantly lower in patients with LOH at 3p21, particularly in TP53 mutant tumors. Examining patient outcome, we found that in squamous cell carcinomas, having any LOH in this region was associated with a better overall survival (log-rank test, P < 0.04). Together, these results indicate that allelic loss at 3p21 can affect patient outcome, and that this loss may initially be related to carcinogen exposure, but that extension of this loss is related to TP53 mutation status and occupational asbestos exposure.     

Loss of heterozygosity analysis on chromosome 5p defines 5p13-12 as the critical region involved in tumor progression of bladder carcinomas

We have previously observed loss of heterozygosity (LOH) at a single locus (del-27) on human chromosome 5p13-12 to correlate with bladder tumor progression. In this study, we examined 33 bladder tumors for their pattern of allelic loss on chromosome 5p using 7 microsatellite markers. In 14 of 15 bladder tumors with LOH at locus del-27, allelic loss was confined to chromosomal region 5p13-12. This region included the microsatellite marker D5S2025 that showed LOH in 5 of 11 (45%) informative cases with LOH at del-27. This suggests that D5S2025 and del-27 are located within a single critical region of LOH on 5p13-12 harboring a tumor suppressor gene involved in bladder tumor progression. Recurrent LOH at other loci was observed at microsatellite markers located at 5p15. However, these losses appeared to be independent of LOH at 5p13-12 and occurred predominantly in poorly differentiated (G3) and advanced (T3-T4) tumors.     

Comprehensive allelotyping of human intrahepatic cholangiocarcinoma.

We performed a genome-wide scan for loss of heterozygosity (LOH) in 22 intrahepatic cholangiocarcinoma (ICC) cases using 168 polymorphic microsatellite markers throughout all of the human chromosomes and 48 markers of which LOH is reportedly characteristic of hepatocellular carcinoma (HCC). Markers with LOH in more than 30% of informative cases were observed at 21 loci. Among these, eight markers on 6q (three loci), 4q (two loci), 9q, 16q, and 17p shared high frequencies of LOH with HCC in our previous study. As for gross appearance, mass-forming type tumors showed higher frequency of LOH (P < 0.001) compared with other types. Compared by tumor size (< or =5 cm versus >5 cm), number (multiple versus solitary), and the International Union Against Cancer TNM classification (stage IVB versus II-IVA), LOH was observed more frequently in advanced stages (P < 0.01, respectively). However, LOH frequency does not differ regardless of lymph node status (pN0 versus pN1). Frequent LOH on 1p36 including the p73 locus was noted in large tumors without lymph node metastasis. These suggest that ICC shares some common carcinogenic steps with HCC such as LOH of 4q and 6q and that inactivation of tumor suppressor genes on chromosome 1p36 contributes to progression of ICC but not to metastatic traits.     

Molecular and cellular characterization of human renal cell carcinoma cell lines.

Recent studies have suggested that a tumor suppressor gene located in the region 3p21-26 of chromosome 3 is essential to the genesis of sporadic renal cell carcinoma (RCC) and that other tumor suppressor genes located on other chromosomes may be involved with progression of this malignancy. The cellular heterogeneity of solid tumors complicates their analysis. In order to analyze a homogeneous population of tumor cells and identify genetic changes associated with histology in renal cortical tumors, we have established and characterized 35 RCC lines derived from tumor tissue from 31 patients with renal cell carcinomas. The overall success rate in establishing these cell lines from fresh or frozen specimens was 75% (18 of 24) and 35% (17 of 48), respectively. These lines differed in their morphology, growth rates, and tumorigenicity in athymic nude mice. Molecular characterization utilizing DNA fingerprinting and restriction fragment length polymorphism deletion analysis was performed to detect somatic mutations and loss of heterozygosity on the short arm of chromosome 3. Analysis revealed loss of heterozygosity on chromosome 3p in 25 cell lines derived from 28 informative nonpapillary forms of RCC (89%). Deletion-mapping analysis showed the retention of the distal locus, D3S18, in one of the RCC cell lines, which further localized the position of the putative tumor suppressor gene to the region proximal to D3S18. Although deletions on chromosome 3 have been recently suggested to be specific to the clear cell-type phenotype, our results revealed no correlation between loss of heterozygosity and clear or granular cell types.     

Low frequency of HLA haplotype loss associated with loss of heterozygocity in chromosome region 6p21 in clear renal cell carcinomas

HLA class I loss or downregulation is a widespread mechanism used by tumor cells to avoid tumor recognition by cytotoxic T lymphocytes favoring tumor immune escape. Multiple molecular mechanisms are responsible for these altered HLA class I tumor phenotypes. It has been described in different epithelial tumors that loss of heterozygosity (LOH) at chromosome region 6p21.3 is a frequent mechanism that leads to HLA haplotype loss, ranging between 40 and 50%, depending on the tumor entity analyzed. Here we have tested the frequency of LOH at 6p21 chromosome region in Renal Cell Carcinomas (RCC) of the clear cell and chromophobe subtype. A low frequency of HLA haplotype loss (6.6%) was found in clear cell RCC. These data significantly differ from those reported in other epithelial tumors. In contrast, in RCC of chromophobe subtype this frequency was 10 times higher (3 out of 5 cases analyzed). These results indicate that LOH at 6p21.3 is not a frequent mechanism that leads to HLA class I abnormalities in clear cell RCC. In addition, the chromophobe RCC subtypes differ not only in histopathological criteria but also in the frequency of LOH-mediating HLA class I alterations. These results might help to understand the significantly different biological behavior of both RCC subtypes.