V.V.V.S. Murty

Abnormalities at chromosome region 3p12–14 characterize clear cell renal carcinoma

In an effort to determine whether or not any characteristic chromosomal abnormalities exist in renal cancer, cytogenetic findings were correlated with tumor histology in nine cases of renal adenocarcinoma. Metaphase preparations adequate for analysis were obtained from cultures harvested between day 3 and day 21. Model chromosome number was diploid in three cases, hypodiploid in three, and hyperdiploid in the remaining three. One clear cell adenocarcinoma failed to reveal any chromosomal abnormality. Two tumors, a tubular/papillary carcinoma and an acinar/papillary carcinoma, showed the clonal abnormalities del(1)(p2l),+2,+7,+8,+12,+13,+16,+17,-21 and t(2;10)(q14-21;q26),+7q,+11q,-18, respectively. Interestingly, five of six clear cell tumors studied had clonal abnormalities affecting the short arm of chromosome #3 in the 3p12-21 region, and in the remaining case, of 15 karyotyped metaphases suitable for interpretation, one showed a deletion in 3p. These data indicate that clear cell carcinoma of the kidney may be associated with a nonrandom chromosomal abnormality involving the 3p12-14 region.

The gene for fibroblast activation protein α (FAP), a putative cell surface-bound serine protease expressed in cancer stroma and wound healing, maps to chromosome band 2q23

The human fibroblast activation protein {alpha} (FAP{alpha}) is an inducible cell surface glycoprotein of M{sub r} 95,000 recognized by a number of monoclonal antibodies (mAbs), including the prototype mAb F19. Immunohistochemical studies have shown that FAP{alpha} expression in vivo is tightly regulated, with transient expression in some fetal mesenchymal tissues but absence of expression in most normal adult tissues. Reexpression of FAP{alpha} is observed in the reactive stromal fibroblasts of several common types of epithelial cancers, including >90% of breast, colorectal, and lung carcinomas and healing wounds. Cloning and sequence analysis of an FAP{alpha}-specific cDNA has revealed that the molecule is encoded by a novel gene, FAP, which shows sequence similarity to members of the serine protease family of integral membrane proteins, namely dipeptidyl peptidase IV (DPPIV, also known as lymphocyte activation antigen, CD26, or adenosine dearoinase binding protein) and DPPX, a DPPIV-related molecule of unknown function. 15 refs., 1 fig.

Confirmation of Duffy blood group antigen locus (FY) at 1q22→q23 by fluorescence in situ hybridization

The gene for the Duffy blood group antigen (FY) was previously assigned to the chromosome region 1q22-->q23 by linkage analysis. We confirm this localization by fluorescence in situ hybridization.

Assignment of the human TYRP (brown) locus to chromosome region 9p23 by nonradioactive in situ hybridization

The TYRP (brown) locus determines pigmentation and coat color in the mouse. The human homolog of the TYRP locus has been recently identified and shown to encode a 75-kDa transmembrane melanosomal glycoprotein called gp75. The gp75 glycoprotein is homologous to tyrosinase, an enzyme involved in the synthesis of melanin, forming a family of tyrosinase-related proteins. A genomic clone of human gp75 was used to map the human TYRP locus to chromosome 9, region 9p23, by nonradioactive fluorescent in situ hybridization. Specificity of hybridization was tested with a genomic fragment of human tyrosinase that mapped to a distinct site on 11q21. The 9p region has been reported to be nonrandomly altered in human melanoma, suggesting a role for the region near the TYRP locus in melanocyte transformation.

Nonsyntenic Amplification of MYC with CDK4 and MDM2 in a Malignant Mixed Tumor of Salivary Gland

Karyotypic analysis of a metastatic malignant mixed tumor of the salivary gland revealed the presence of double minute chromosomes (dmin), indicative of gene amplification. Comparative genomic hybridization analysis of DNA extracted from the primary and a renal metastasis indicated overt amplification of DNA sequences derived from 8q23-24 and 12q13-15 regions. Subsequent Southern blot analysis of tumor DNA from the metastasis with the use of probes previously mapped to those regions indicated amplification of MYC at 8q23-24 and CDK4 and MDM2 at 12q13-15. Fluorescence in situ hybridization of differentially labeled MYC and MDM2 genes hybridized to tumor metaphase chromosomes revealed an independent nonsyntenic amplification of MYC and MDM2 on dmin in this tumor.

Subregional mapping of 13 single-copy genes on the long arm of chromosome 12 by fluorescence in Situ hybridization

Subregional localization of 13 single-copy DNA sequences previously assigned to the long arm of chromosome 12 has been performed using the fluorescence in situ hybridization (FISH) technique. The following order is suggested for the 13 mapped genes: cen-->COL2A1-->(VDR-D12S15)-->(D12S17-D12S4++ +-D12S14-D12S6)-->D12S8-->(IAPP-MGF- D12S7-D12S12)-->IGF1-->qter. Eight of the mapped genes clustered at two regions, one at 12q13 (D12S17-D12S4-D12S14-D12S6) and the other at 12q22 (IAPP-MGF-D12S7-D12S12). Our results show that single-copy DNA sequences as small as 500 bp can be successfully mapped by FISH.

Subregional mapping of 8 single copy loci to chromosome 6 by fluorescence in situ hybridization

We have subregionally mapped 8 independently derived probes which have been assigned to chromosome 6 (D6S61, D6S134, D6S149, D6S155, MACS, VIL2, IGF2R and PLG) by FISH. All the probes were mapped to the long arm of chromosome 6 except D6S61, which was assigned to the short arm at 6p25. The remaining probes were clustered at the 6q25-->q27 region except MACS which was mapped to 6q22.2.

Confirmation of 15q26.1 as the site of the FES protooncogene by fluorescence in situ hybridization

The FES oncogene was previously localized to human chromosome 15 by analysis of mouse x human somatic cell hybrids and to 15q26 by in situ hybridization of a radioactively labeled probe. In the present study, using fluorescence in situ hybridization, we have determined the precise map position of FES at 15q26.1.

Molecular Genetics in Germ Cell Tumours

Publisher Summary This chapter discusses molecular genetics in germ cell tumors (GCT). GCTs in the male arise in spermatogonial cells; they are heterogeneous, and some subsets exhibit embryonal-like differentiation. Therefore, they provide unusual opportunities for the analysis of the genetic basis of malignant transformation and differentiation in a stem cell system of unique destiny. GCTs are present in gonadal or extragonadal sites and histologically comprise seminomas and nonseminomas. The genetic basis of transformation in germ cells and regulation of in vivo differentiation in this complex tumor system remain largely unknown. This chapter presents a summary of current results of the cytogenetic and molecular analyses of male GCTs. These studies have led to a new model of transformation of a germ cell in differentiation. The model, unlike the currently well-established models of tumorigenic transformation calls for rescue, by amplification and over expression of a key gene or genes, of a cell otherwise destined to die because of inability to complete the developmental program. The chapter also discusses the studies initiated to identify specific genetic alterations that may release constraints on embryonal-like differentiation of a germ cell independently of fertilization.