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Biomedical subjects

K Kok

Publications and source records attributed to K Kok.

At least 19 recordsLinked to original sources
PubMed2001

Allelic gains and losses in distinct regions of chromosome 6 in gastric carcinoma.

In gastric cancer, alterations in the long arm of chromosome 6 are a frequent event. Two regions of heterozygous loss have been described: 6q16.3-6q23 and 6q26-6q27. We have evaluated by microsatellite and FISH analyses the 6q status of three cell lines that we established from primary gastric carcinomas xenografted in nude mice, in order to elucidate the underlying mechanisms of 6q alterations. Alterations of the long arm of chromosome 6 were found in all three xenografts and corresponding cell lines. Allelic imbalance (AI) was found in the three cases, by microsatellite analysis. Fluorescence in situ hybridization analyses clearly demonstrated a duplication of the larger part of the 6q arm in all three cell lines. Two of the cell lines and the corresponding xenografts showed, in addition, complete loss of one of the parental alleles at the terminal part of 6q. Thus, the AI observed along the long arm of chromosome 6 is represented by gain of alleles in one distinct chromosomal segment and loss of alleles in another distinct segment.

Allelic Imbalance↗
PubMed2000

The ubiquitin-activating enzyme E1-like protein in lung cancer cell lines.

The UBE1L gene isolated from the chromosome 3p21 region has an extremely reduced level of mRNA in lung cancer. Sequence analysis showed a 45% homology to the human ubiquitin-activating enzyme E1 at the amino acid level. To further characterize the protein product, we generated UBE1L protein-specific antibodies. Immunoblot analysis revealed a full-length gene product of approximately 112 kDa. Assessment of the level and distribution pattern of the UBE1L protein in normal and tumor tissue using the generated antibodies showed that the UBE1L protein was present in normal lung cells and non-lung cancer cell lines, but was undetectable in all 14 human lung cancer cell lines analyzed. This difference in expression of the UBE1L protein between normal lung tissue and lung tumor-derived cell lines suggests a possible involvement of an E1-like protein in the origin and/or progression of lung tumors.

Blotting, Western↗
PubMed2000

Inclusion of new microsatellite repeats in allelic loss analysis excludes retention of heterozygosity in the renal cell carcinoma critical region in 3p21.

A variety of human cancers, including renal cell carcinoma (RCC), show frequent heterozygous deletion events in 3p21.3. An approximate 400-kb segment from within 3p21.3 is suspect of harboring a tumor suppressor gene, as it is homozygously deleted in three lung cancer cell lines and heterozygously deleted in virtually all lung tumors. Loss of heterozygosity (LOH) studies of this segment are hampered by the absence of highly informative markers. We have identified several new nucleotide repeats that map within this region, and have used these to complement our previous LOH studies in RCC. Our present analysis clearly shows that the common region of homozygous deletions in the lung cancer cell lines is always contained within the smallest region of overlap of heterozygous deletions in RCC.

Alleles↗
PubMed1999

An evolutionary rearrangement of the Xp11.3-11.23 region in 3p21.3, a region frequently deleted in a variety of cancers.

In searching for a tumor suppressor gene in the 3p21.3 region, we isolated two genes, RBM5 and RBM6. Sequence analysis indicated that these genes share similarity. RBM5 and-to a lesser extent-RBM6 also have similarity to DXS8237E at Xp11.3-11.23, which maps less than 20 kb upstream of UBE1. A homologue of UBE1, UBE1L, is located at 3p21. 3. FISH analysis showed that the distance between UBE1L and RBM5 in 3p21.3 is about 265 kb. DXS8237E and UBE1 on the X chromosome have the same orientation, whereas on chromosome 3 the orientation of RBM5 and that of RBM6 are opposite to the orientation of UBE1L. Presumably, part of the Xp11.3-11.23 region has duplicated to chromosome 3. Part of this region on chromosome 3 may subsequently have duplicated again within the same chromosomal region. Inversion at some stage of the evolution of the human genome would explain the change in orientation of the genes on chromosome 3 compared with that of the genes on the X chromosome.

Animals↗
PubMed1999

An EGP-2/Ep-CAM-expressing transgenic rat model to evaluate antibody-mediated immunotherapy.

The human pancarcinoma-associated epithelial glycoprotein-2 (EGP-2), also known as 17-1A or Ep-CAM, is a 38-kDa transmembrane antigen, commonly used for targeted immunotherapy of carcinomas. Although strongly expressed by most carcinomas, EGP-2 is also expressed in most simple epithelia. To evaluate treatment-associated effects and side-effects on tumor and normal tissue respectively, we generated an EGP-2-expressing transgenic Wistar rat. To express the cDNA of the EGP-2 in an epithelium-specific manner, the 5' and 3' distal flanking regions of the human keratin 18 (K18) gene were used. EGP-2 protein expression was observed in the liver and pancreas, whereas EGP-2 mRNA could also be detected in lung, intestine, stomach and kidney tissues. In this rat, EGP-2-positive tumors can be induced by injecting a rat-derived carcinoma cell line transfected with the GA733-2 cDNA encoding EGP-2. Transgenic rats were used to study specific in vivo localization of an i.v. anti-EGP-2 monoclonal antibody, MOC31, applied i.v. Immunohistochemical analyses showed the specific localization of MOC31 in s.c. induced EGP-2-positive tumors, as well as in the liver. In contrast, in EGP-2-transgenic rats, MOC31 did not bind to EGP-2-negative tumors, the pancreas, or other normal tissues in vivo. In conclusion, an EGP-2-transgenic rat model has been generated that serves as a model to evaluate the efficacy and safety of a variety of anti-EGP-2-based immunotherapeutic modalities.

Animals↗
PubMed1999

Needlescopic or minisite cholecystectomy.

Needlescopic or minisite cholecystectomy is laparoscopic cholecystectomy done through tiny ports from 1.4 mm to 3 mm in size. This refinement of conventional laparoscopic cholecystectomy reduces further the invasiveness of the operation and gives an improved cosmetic effect. This series describes the result of 36 needlescopic cholecystectomies done between February 1996 and April 1997. Patients with acute cholecystitis were excluded. There were two conversions to conventional laparoscopic surgery and no conversions to open surgery. Thirty-four patients were successfully treated by this technique. Analgesic consumption and cosmetic result was superior compared to a previous published series of conventionally done cases in the same department.

Adult↗
PubMed1999

Percutaneous endoscopic gastrostomy in children with cancer.

We reviewed the clinical course of 32 children with cancer who received nutrition through a feeding tube placed percutaneously during gastroscopy (PEG). Their median age was 5.1 y (75%, range: 1.8-13.7 y, min: 3.5 mo) when the PEG was done 0.7-23 mo after diagnosis (median: 1.8 mo, 75%; range: 0.9-8 mo). Five of the children underwent bone marrow transplantation with the gastrostomy in place. There was a significant (p = 0.0001) decrease in the median weight-for-age SDS of 0.55 (75%, range: -1.18-0.28) from the time of diagnosis to placement of the gastrostomy. Twenty-two percent of the children had neutrophils < 0.5 x 10(9)l at the time of placement. There were no major postoperative complications. Seventy-two percent of the patients experienced a total of 55 minor and transient complications including leakage of gastric juice (n = 29), superficial wound infections (n = 23), mechanical problems (n = 2), or bleeding (n = 1). There were no documented cases of bacteraemia. Twelve of the wound infections (52%) arose during neutropenic episodes. Two tubes were replaced due to mechanical problems. There was a median increase in weight SDS of 0.3 (75%, range: -0.6-1.1) from the time of placing the gastrostomy to the end of follow-up (p = 0.054). Nutrition via gastrostomy in children with cancer has several advantages. It is rarely associated with more than minor complications, it is cosmetically more acceptable than the nasogastric tube and it improves nutrition at far lower cost than parenteral nutrition. In selected cases in which bone marrow transplantation or intensive treatment protocols are planned, we suggest that a gastrostomy should be considered before malnutrition develops.

Adolescent↗
PubMed1999

Right-sided colonic diverticular disease as a source of lower gastrointestinal bleeding.

Right-sided colonic diverticular disease is a distinct disease entity uncommon in the West. Occasionally, the condition may be complicated by hemorrhage and present as lower gastrointestinal bleeding. We report a series of 25 cases of bleeding right colon diverticulosis and discuss its presentation and management. Patients were selected from the colonoscopic reports of all 190 patients presented with suspected acute lower gastrointestinal bleeding in National University Hospital, Singapore, from 1988 to 1994. Fifty-seven patients (30%) had bleeding diverticulosis in which 25 patients (44%) suffered from right-sided disease. Sixty-four per cent of patients had a history of hypertension. Patients presented with either fresh blood in stools or melena. Fifteen patients (60%) required blood transfusion (median, 2 units). Colonoscopy showed blood clots in the right colon in 15 cases (60%) and active bleeding from the right colon diverticula in 3 patients (12%). The bleeding stopped spontaneously in 16 patients (64%). The other 9 patients required surgery because of continuous or recurrent bleeding. All had a right hemicolectomy performed. The hospital stay was 13 days in this group, compared with 5 days for those undergoing conservative treatment (P = 0.0004). There were no deaths. No patients had further bleeding episodes during a median 7-month follow-up.

Acute Disease↗
PubMed1999

Substantial reduction of the gastric carcinoma critical region at 6q16.3-q23.1.

Deletions of the long arm of chromosome 6 are a common event in gastric carcinomas. In a previous study, deletion mapping of 6q identified two smallest regions of overlap (SROs) of heterozygous deletions: one interstitial, spanning 12-16 cM, bordered by D6S268 (6q16.3-q21) and ARG1 (6q22.3-q23.1), and one distal to IFNGR1 (6q23-q24), spanning more than 30 cM. Loss of heterozygosity (LOH) of the interstitial SRO was detected in 50% of informative tumors. We analyzed 60 primary gastric tumors with 19 highly polymorphic markers from 6q16.3-q23.3 to delimit the interstitial SRO further. Of the 50 tumors that were informative for at least one locus, 18 (36%) showed allelic imbalance (AI). The overlap of these cases allowed us to define an SRO of approximately 3 Mb flanked by D6S278 and D6S404. AI or LOH of this region occurs in all histologic types of gastric carcinoma and in early stages of development, indicating that loss of a gene from this region of 6q is a crucial step in a main route of gastric carcinogenesis. For cases with retention of 6q, alternative routes of gastric carcinogenesis may exist. Genes Chromosomes Cancer 26:29-34, 1999.

Chromosome Deletion↗
PubMed1997

Normal FHIT transcripts in renal cell cancer- and lung cancer-derived cell lines, including a cell line with a homozygous deletion in the FRA3B region.

The recently identified FHIT gene encompasses the FRA3B region and the breakpoint of a constitutive t(3;8) occurring in a family with hereditary renal cell cancer. Occurrence of aberrant transcripts in different types of tumours has led to the suggestion that FHIT might play a critical role in the development of various types of cancer. We have analyzed the gene and its transcripts in lung cancers and renal cell cancer-derived cell lines. A lung adenocarcinoma cell line, GLC-A2, appeared to have a homozygous deletion in intron 5 of FHIT. RT-PCR analysis revealed a normal-sized PCR product in all of the cell lines: Including GLC-A2. A number of them had an additional aberrant product. Analysis of a great number of control cell lines and tissues showed that the majority of these also had aberrant PCR products in addition to a normal-sized PCR product. Different specimens of the same cell type showed variable additional RT-PCR products. Normal-sized PCR products had a sequence identical to the FHIT sequence. PCR products longer than normal had insertions of different sizes at different positions. With three exceptions, PCR products shorter than normal represented FHIT sequences missing one or more entire exons. Thus, the presence of aberrant transcripts is not cancer-specific. Conceivably, sequence responsible for the instability of the FRA3B region are being transcribed into FHIT pre-mRNA and may cause the abnormal splicing and processing of the transcripts.

Acid Anhydride Hydrolases↗
PubMed1997

Deletions of the short arm of chromosome 3 in solid tumors and the search for suppressor genes.

The concept that cells can become malignant upon the elimination of parts of chromosomes inhibiting cell division dates back to Boveri in 1914. Deletions occurring in tumor cells are therefore considered a first indication of possible locations of tumor suppressor gene. Approaches used to localize and identify the paradigm of tumor suppressors, RB1, have also been applied to localize tumor suppressor genes on 3p, the short arm of chromosome 3. This review discusses the methodological advantages and limitations of the various approaches. From a review of the literature on losses of 3p in different types of solid tumors it appears that some tumor types show involvement of the same region, while between others the regions involved clearly differ. Also discussed are results of functional assays of tumor suppression by transfer of part of chromosome 3 into tumor cell lines. The likelihood that a common region of deletions would contain a tumor suppressor is strongly enhanced by coincidence of that region with a chromosome fragment suppressing tumorigenicity upon introduction in tumor cells. Such a situation exists for a region in 3p21.3 as well as for one or more in 3p12-p14. The former region is considered the location of a lung cancer suppressor. The same gene or a different one in the same region may also play a role in the development of other cancers including renal cell cancer. In the latter cancer, there may be additional roles of the VHL region and/or a 3p12-p14 region. The breakpoint region of a t(3;8) originally found to be constitutively present in a family with hereditary renal cell cancer now seems to be excluded from such a role. Specific genes on 3p have been suggested to act as suppressor genes based on either their location in a common deletion region, a markedly reduced expression or presence of aberrant transcripts, their capacity to suppress tumorigenicity upon transfection in to tumor cells, the presumed function of the gene product, or a combination of several of these criteria. A number of genes are evaluated for their possible role as a tumor suppressor according to these criteria. General agreement on such a role seems to exist only for VHL. Though hMLH1 plays an obvious role in the development of specific mismatch repair-deficient cancers, it cannot revert the tumor phenotype and therefore cannot be considered a proper tumor suppressor. The involvement of VHL and MLH1 also in some specific hereditary cancers allowed to successfully apply linkage analysis for their localization. TGFBR2 might well have a tumor suppressor function. It does reduce tumorigenicity upon transfection. Other 3p genes coding for receptor proteins THRB and RARB, are unlikely candidates for tumor suppression. Present observations on a possible association of FHIT with tumor development leave a number of questions unanswered, so that provisionally it cannot be considered a tumor suppressor. Regions that have been identified as crucial in solid tumor development appear to be at the edge of synteny blocks that have been rearranged through the chromosome evolution which led to the formation of human chromosome 3. Although this may merely represent a chance occurrence, it might also reflect areas of genomic instability.

Adaptor Proteins, Signal Transducing↗
PubMed1996

An 80 Kb P1 clone from chromosome 3p21.3 suppresses tumor growth in vivo.

High frequencies of allelic loss on the short arm of chromosome 3 in small cell lung cancer (SCLC) and a number of other tumors suggest the existence of a tumor suppressor gene(s) within the deleted regions. Two small cell lung cancer lines, NCI H740 and GLC20, have been described which have homozygous deletions in the region 3p21.3. The deleted region overlaps with a 2 Mb fragment of human DNA present in the interspecies hybrid HA(3)BB9F, that suppresses tumor formation by mouse A9 fibrosarcoma cells. Human sequences from this cell hybrid were isolated using inter Alu PCR. From this starting point, a P1 contig was developed for the region of 450 Kb that is common to the homozygous deletions seen in the SCLC lines NCI H740 and GLC20 and is also present in HA(3)BB9F, the suppressed A9 hybrid. Individual P1 clones were assayed for their ability to suppress the tumorigenicity of the mouse fibrosarcoma cell line A9 as assayed by injection of transfected A9 cells into athymic nude mice. The introduction of one of the P1 clones into A9 cells resulted in suppression of tumor growth whereas two other P1 clones from the contig failed to suppress tumor formation in athymic nude mice. These data functionally delimit a tumor suppressor locus to a region of 80 kb within a P1 clone at 3p21.3.

Animals↗
PubMed1996

Isolation of the human semaphorin III/F gene (SEMA3F) at chromosome 3p21, a region deleted in lung cancer.

Small cell lung cancer (SCLC) has been correlated with a deletion in the short arm of chromosome 3, with the region 3p21 being lost from one homolog in almost all cases. Two SCLC cell lines have homozygous deletions in 3p21, and these deletions overlap with a fragment of chromosome 3 that has tumor suppression activity in vivo. We have isolated some cDNA clones from this region that are homologous to the genes constituting the semaphorin family. They represent a novel human semaphorin, termed sema III/F (HGMW-approved symbol SEMA3F), which is expressed as a 3.8-kb transcript in a variety of cell lines and tissues; it is detected as early as Embryonic Day 10 in mouse development. There is high expression in mammary gland, kidney, fetal brain, and lung and lower expression in heart and liver. Although there is reduced expression of this gene in several SCLC lines, no mutations were found. This semaphorin homolog has characteristics of a secreted member of the semaphorin III family, with 52% identity with mouse semaphorin E and 49% identity with chicken collapsin/semaphorin D.

Amino Acid Sequence↗
PubMed1996

Major role for a 3p21 region and lack of involvement of the t(3;8) breakpoint region in the development of renal cell carcinoma suggested by loss of heterozygosity analysis.

In a loss of heterozygosity analysis of 3p, we examined 44 sporadic cases of renal cell carcinoma (RCC) and matched normal tissue with 18 markers distributed over the whole p-arm. The majority of these markers clustered in three regions that have been suggested to be involved in the development of RCC, namely the p25 region, where the von Hippel Lindau (VHL) gene is located; the p21 region, which has been identified as a common region of overlap (SRO) of heterozygous deletions; and the p14 region, which is the location of the constitutional t(3;8) breakpoint occurring in an RCC family. Thirty-one out of these 44 tumors were analyzed with 9 additional markers from the 3p12-14 region to further delimit the SRO in this region. Our analysis shows that when deletions were detected the 3p21 region was always included. The 3p21 markers D3F15S2 and UBEIL were always contained within these 3p21 deletions. The t(3;8) breakpoint region showed the lowest percentage of loss of heterozygosity. Moreover, in three cases the t(3;8) breakpoint region retained heterozygosity, whereas a region more proximal to the breakpoint showed allelic losses. This supports exclusion of the t(3;8) region from a role in the development of sporadic RCC. In a number of tumors, two or three 3p regions with allelic losses were present separated by a region of retention of heterozygosity. In these tumors, deletions at 3p21 occurred in combination with deletions of either the VHL region, or the region proximal to the t(3;8), or both, suggestive of multiple gene involvement in the development of sporadic RCC with a primary role of the 3p21 region.

Carcinoma, Renal Cell↗