Lysosomal acid phosphatase (LAP) is synthesized as a type I membrane glycoprotein and targeted to lysosomes via the plasma membrane. Its cytoplasmic tail harbours a tyrosine‐containing signal for rapid internalization. Expression in Madine‐Darby canine kidney cells results in direct sorting to the basolateral cell surface, rapid endocytosis and delivery to lysosomes. In contrast, a deletion mutant lacking the cytoplasmic tail is delivered to the apical plasma membrane where it accumulates before it is slowly internalized. A chimeric protein, in which the cytoplasmic tail of LAP is fused to the extracytoplasmic and transmembrane domain of the apically sorted haemagglutinin, is sorted to the basolateral plasma membrane. A series of truncation and substitution mutants in the cytoplasmic tail was constructed and comparison of their polarized sorting and internalization revealed that the determinants for basolateral sorting and rapid internalization reside in the same segment of the cytoplasmic tail. The cytoplasmic factors decoding these signals, however, tolerate distinct mutations indicating that different receptors are involved in sorting at the trans‐Golgi network and at the plasma membrane.

We combined laser-assisted microdissection from H&E-stained paraffin sections, degenerated oligonucleotide-primed polymerase chain reaction (DOP-PCR), and comparative genomic hybridization (CGH) to analyse chromosomal imbalances in small tumour areas consisting of 50-100 cells. This approach was used to investigate intratumour genetic heterogeneity in a case of metastatic prostatic adenocarcinoma and chromosomal changes in areas of prostatic intraepithelial neoplasia (PIN) adjacent to the invasive tumour. In four microdissected invasive tumour areas with different histological patterns (acinar, cribriform, papillary and solid) marked intratumour heterogeneity was found by CGH. Recurrent chromosomal imbalances detected in at least two microdissected tumour areas were gains on 1p32-->p36, 2p22, 3q21, 7, 8q21-->q24, 11q12-->q13, 16p12-->p13, 17, 19 and loss on 16q23. Additional chromosomal changes were found in only one of the microdissected areas (gains on 16q21-->q23, 20q22 and losses on 8p21-->p23, 12p11-->q12, 12q21-->q26, 13q21-->q34, 16q12, and 18q22). In PIN, gains on chromosomes 8q21-->q24 and 17 were found in both samples investigated (low and high grade PIN), while gains on chromosomes 7, 11q, 12q, 16p, and 20q and losses on 2p, 8p21-->p23, 12q were found only in one PIN area. Controls to ensure reliable CGH results consisted in CGH analyses of (i) approximately 80 microdissected normal epithelial cells, which showed no aberrations after DOP-PCR and (ii) larger cell numbers (approximately 10(5) or 10(7) cells) of the primary tumour investigated without DOP-PCR and partially displaying the chromosomal imbalances (gain on 16p12-->p13, losses on 2p25, 8p21-->p23, 12p11-->p12, 12q21-->q26, 18q22) found in the small microdissected areas. Microsatellite and FISH analyses further confirmed our CGH results from microdissected cells. The combined approach of laser-assisted microdissection, DOP-PCR and CGH is suitable to identify early genetic changes in PIN and chromosomal imbalances associated with the particular histological patterns of invasive prostatic adenocarcinoma.

Lysosomal acid phosphatase (LAP) is rapidly internalized from the cell surface due to a tyrosine‐containing internalization signal in its 19 amino acid cytoplasmic tail. Measuring the internalization of a series of LAP cytoplasmic tail truncation and substitution mutants revealed that the N‐terminal 12 amino acids of the cytoplasmic tail are sufficient for rapid endocytosis and that the hexapeptide 411‐PGYRHV‐416 is the tyrosine‐containing internalization signal. Truncation and substitution mutants of amino acid residues following Val416 can prevent internalization even though these residues do not belong to the internalization signal. It was shown recently that part of the LAP cytoplasmic tail peptide corresponding to 410‐PPGY‐413 forms a well‐ordered beta turn structure in solution. Two‐dimensional NMR spectroscopy of two modified LAP tail peptides, in which the single tyrosine was substituted either by phenylalanine or by alanine, revealed that the tendency to form a beta turn is reduced by 25% in the phenylalanine‐containing peptide and by approximately 50% in the alanine‐containing mutant peptide. Our results suggest, that in the short cytoplasmic tail of LAP tyrosine is required for stabilization of the right turn and that the aromatic ring system of the tyrosine residue is a contact point to the putative cytoplasmic receptor.

Comparative genomic hybridisation (CGH) is based on a two-colour, competitive fluorescence in situ hybridisation of differentially labelled tumour and reference DNA to normal metaphase chromosomes. This new technology has made a great impact in molecular tumour pathology due to its possible application to archival specimens and the ability to create copy number karyotypes throughout the whole genome from very small amounts of DNA. If chromosomal imbalances can be correlated with a etiological and clinical features of tumours, CGH could be able to provide new prognostic and diagnostic criteria. CGH findings further provide starting points for the molecular genetic characterisation of altered chromosomal regions harbouring yet unidentified genes involved in tumorigenesis and tumour progression. An overview of the results of published CGH studies on solid tumours and haematological malignancies is presented. Methodological limitations of the CGH technology are reported, as well as future developments which will improve its use in routine analysis.

Fluorescence in situ hybridization (FISH) using chromosome-specific alpha-satellite DNA probes for chromosomes 7, 8, and 12 was performed on paraffin-embedded tissue sections and touch imprint preparations of 53 cases of human prostate cancer. Subsequent haematoxylin and eosin (H & E) staining of the hybridized tissue sections allowed unambiguous assignment of hybridization signals either to tumour or to non-tumorous parenchyma. Fifty-three cases of human prostate cancer were evaluated for numerical aberrations of chromosome 7. Scoring 200 cells of tumour and non-tumorous parenchyma in each case revealed abnormalities exclusively in tumour parenchyma in 41 cases (77 per cent). Ten of 41 cases (24 per cent) showed trisomy 7, and 15 cases (37 per cent) monosomy 7 or trisomy 7 in combination with monosomy 7, respectively. Sixteen cases (39 per cent) exhibited polysomy 7 in cells of the tumour parenchyma. In the tumour tissue in one case, different polyploid clones (triploid, tetraploid) and polysomy 7 could be identified by double hybridization with chromosome-specific DNA probes for chromosome 7, plus 8 or 12. The indicated numerical aberrations of chromosome 7 were correlated with 78 per cent of advanced pathological stages or poorly differentiated tumours (pT3/4 or G3) of prostate carcinomas. A statistical analysis of the data revealed significant relationships of particular numerical abnormalities of chromosome 7 to different pathological categories (pT, G, pN) of tumour classification. For the T-classification, the frequency of cells carrying polysomy 7 and polysomy 7/+7 increases significantly from pT1 to pT3/4 (P = 0.022).(ABSTRACT TRUNCATED AT 250 WORDS)