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Deletion of chromosome arm 6q is a frequent karyotypic alteration found in a variety of cancers and lymphoproliferative disorders, including leukemia and lymphomas. We characterized 6q deletions in 35 malignant lymphomas, using conventional and molecular cytogenetic approaches, to define the deletion pattern of 6q in different histological types. Conventional cytogenetics revealed a 6q deletion in 46% of lymphomas, including two cases that showed 6q deletion as the sole chromosome anomaly. Interphase FISH analysis demonstrated allelic loss of 6q regions in 33 out of 35 cases (94.2%); the deletions were discontinuous, involving nonadjacent molecular regions. Although 6q deletion is a common event in all types of lymphomas, specific deletion patterns seem to characterize different histological types, suggesting that different tumor suppressor genes play different roles in different types of lymphomas. Two specific 6q regions deleted in diffuse large B cell lymphomas but not in follicular lymphomas may be implicated in the clinical transformation.

Purpose: We used conventional cytogenetics, molecular cytogenetics, and molecular genetic analyses to study the pattern of allelic loss on chromosome 6q in a cohort of borderline epithelial ovarian tumors., Experimental Design: Fifteen tumor samples were collected from patients undergoing surgery for ovarian tumors. The tumors of borderline malignancy, classified according to the standard criteria, included 4 mucinous and 11 serous tumors. Cytogenetic and molecular cytogenetic (with yeast artificial chromosome clones from 6q26-27) studies were performed on tumor areas contiguous to those used for histological examination ensuring the appropriate sampling. Moreover loss of heterozygosity analysis was performed using PCR amplification of eight microsatellite markers mapping on 6q27 (D6S193, D6S297), 6q26 (D6S305, D6S415, D6S441), 6q21 (D6S287), 6q16 (D6S311), and 6q14 (D6S300)., Results: Deletions of this chromosome arm, in particular of 6q24-27, were the most frequent lesions found in this set of tumors. In a tumor with a normal karyotype the only detectable alteration was a deletion of approximately 300 kb within the D6S149-D6S193 interval at band 6q27. This is, to date, the smallest deletion described for borderline tumors., Conclusion: Alterations in the above-mentioned interval are a common finding in advanced ovarian carcinomas but also in benign ovarian cysts, implying that some tumors of borderline malignancy may arise from benign tumors and that malignant ones may evolve from tumors of borderline malignancy. Genes located in 6q27 seem to be crucial for this mechanism of early events in ovarian tumorigenesis.

Cytogenetic, molecular and functional analysis has shown that chromosome region 6q27 harbors a senescence inducing gene and a tumor suppressor gene involved in several solid and hematologic malignancies. We have cloned at 6q27 and characterized the RNASE6PL gene which belongs to a family of cytoplasmic RNases highly conserved from plants, to man. Analysis of 55 primary ovarian tumors and several ovarian tumor cell lines indicated that the RNASE6PL gene is not mutated in tumor tissues, but its expression is significantly reduced in 30% of primary ovarian tumors and in 75% of ovarian tumor cell lines. The promoter region of the gene was unaffected in tumors cell lines. Transfection of RNASE6PL cDNA into HEY4 and SG10G ovarian tumor cell lines suppressed tumorigenicity in nude mice. When tumors were induced by RNASE6PL-transfected cells, they completely lacked expression of RNASE6PL cDNA. Tumorigenicity was suppressed also in RNASE6PL-transfected pRPcT1/H6cl2T cells, derived from a human/mouse monochromosomic hybrid carrying a human chromosome 6 deleted at 6q27. Moreover, 63.6% of HEY4 clones and 42.8% of the clones of XP12ROSV, a Xeroderma pigmentosum SV40-immortalized cell line, transfected with RNASE6PL cDNA, developed a marked senescence process during in vitro growth. We therefore propose that RNASE6PL may be a candidate for the 6q27 senescence inducing and class II tumor suppressor gene in ovarian cancer.

To assess whether early breast lesions are the precursors of invasive carcinomas, three classes of breast lesions, namely benign tumors (including fibroadenomas), putative premalignant lesions (including cases of atypical hyperplasia), and invasive carcinomas, were compared at the cytogenetic and molecular cytogenetic levels. Genetic relatedness was clearly demonstrated by the sharing of several anomalies, among which 6q deletions outnumbered all of the other alterations detected. Indeed, deletions of the long arm of chromosome 6, most likely occurring in epithelial cells, were present in 83.9% of benign breast tumors, 64% of putative premalignant lesions, and 77.4% of analyzable carcinomas. Furthermore, the interval between 6q24 and qter appeared to be the common region of deletion in all three classes of breast lesions, whereas the minimal common region of deletion was 6q27-qter. Interestingly, the latter region was reported previously to be deleted in benign ovarian tumors and recently found to harbor a gene (SEN6) that is important for SV40-mediated immortalization of human cells.

A detailed long range restriction map of the region defined by markers D6S149 and D6S193 on chromosome 6q27 has been constructed. This was achieved by YAC cloning and contig assembling of the same region. Seven YAC clones were found to span the almost 1000 Kb region flanked by the two markers which on the genetic map resulted to be 1.9 cM apart. With some of the characterized YAC clones we undertook a molecular cytogenetic analysis of 20 benign ovarian tumors. The rationale for this was the recent mapping to a region of chromosome 6q27, flanked by markers D6281 and D6S133, of a locus for the SV40-mediated immortalization of human cells (SEN6 gene). Noteworthy we found that the the D6S149-D6S193 region (comprised in the larger D6S281-D6S133 physical interval) was altered in all samples analysed adding support to the occurrence of a immortalization step in this type of tumors.

Cytogenetic investigation was performed on direct preparations of 15 endometrial cancers showing different histotypes. Clonal abnormalities were found in 11 out of 13 analysable cases. The modal chromosome number was near diploid in all cases. The abnormal karyotypes contained relatively simple numerical or structural aberrations in the majority of tumours. In contrast, two neoplasms with serous papillary and mixed mullerian morphological features shared multiple complex changes as well as cytogenetic evidence of intratumoral heterogeneity. The most frequent chromosome abnormality in our series of endometrial neoplasms was 6q deletion, which was detected in serous papillary, endometrioid and mixed mullerian tumours. The loss of the 6q region, which is also frequently involved in ovarian carcinoma, suggests a relationship between endometrial and ovarian cancers based on a common histogenesis.

Complex karyotypes are often seen in primary surface epithelial ovarian tumors (SEOTs). Conventional cytogenetic as well as fluorescence in situ hybridization analyses coupled with loss of heterozygosity studies identified abnormalities of chromosome 6 as one of the most frequent lesions in these types of tumors. We performed cytogenetic analysis of direct preparations from 40 SEOTs, including borderline tumors and low-, intermediate-, and high-grade carcinomas to verify the frequency of chromosome 6 alterations. We also carried out fluorescence in situ hybridization analysis with a chromosome 6 library and yeast artificial chromosome clones from a region of the same chromosome (6q27). Chromosome 6 abnormalities were identified in 30 of 32 analyzable SEOTs. Twenty-five of 32 cases showed a deletion of 6q irrespective of their histological grade. We wish to underline that this is the first report proving that del(6q) was the most frequent chromosome anomaly in near-diploid SEOTs and that it was the sole anomaly observed in four SEOTs with diploid complement. Our findings suggest that abnormalities of the telomeric region of chromosome 6 (6q27) may be considered one of the earliest lesions in the pathogenesis of ovarian carcinomas.