Immortalization of a human colorectal adenoma cell line by continuous in vitro passage: possible involvement of chromosome 1 in tumour progression

5-Aminosalicylic acid inhibits stem cell function in human adenoma-derived cells: implications for chemoprophylaxis in colorectal tumorigenesis

Background

Most colorectal cancers (CRC) arise sporadically from precursor lesions: colonic polyps. Polyp resection prevents progression to CRC. Risk of future polyps is proportional to the number and size of polyps detected at screening, allowing identification of high-risk individuals who may benefit from effective chemoprophylaxis. We aimed to investigate the potential of 5-aminosalicylic acid (5-ASA), a medication used in the treatment of ulcerative colitis, as a possible preventative agent for sporadic CRC.

Methods

Human colorectal adenoma (PC/AA/C1, S/AN/C1 and S/RG/C2), transformed adenoma PC/AA/C1/SB10 and carcinoma cell lines (LS174T and SW620) were treated with 5-ASA. The effect on growth in two- and three-dimensional (3D) culture, β-catenin transcriptional activity and on cancer stemness properties of the cells were investigated.

Results

5-ASA was shown, in vitro, to inhibit the growth of adenoma cells and suppress β-catenin transcriptional activity. Downregulation of β-catenin was found to repress expression of stem cell marker LGR5 (leucine-rich G protein-coupled receptor-5) and functionally suppress stemness in human adenoma and carcinoma cells using 3D models of tumorigenesis.

Conclusions

5-ASA can suppress the cancer stem phenotype in adenoma-derived cells. Affordable and well-tolerated, 5-ASA is an outstanding candidate as a chemoprophylactic medication to reduce the risk of colorectal polyps and CRC in those at high risk.

Targeting Notch3 in Hepatocellular Carcinoma: Molecular Mechanisms and Therapeutic Perspectives

The Notch signaling pathway is a very conserved system that controls embryonic cell fate decisions and the maintenance of adult stem cells through cell to cell communication. Accumulating evidence support the relevance of Notch signaling in different human diseases and it is one of the most commonly activated signaling pathways in cancer. This review focuses mainly on the role of Notch3 signaling in hepatocellular carcinoma and its potential therapeutic applications against this malignancy. In this regard, the crosstalk between Notch and p53 may play an important role.

Cellular Response upon Stress: p57 Contribution to the Final Outcome

Progression through the cell cycle is one of the most important decisions during the life of a cell and several kinds of stress are able to influence this choice. p57 is a cyclin-dependent kinase inhibitor belonging to the CIP/KIP family and is a well-known regulator of the cell cycle during embryogenesis and tissue differentiation. p57 loss has been reported in a variety of cancers and great effort has been spent during the past years studying the mechanisms of p57 regulation and the effects of p57 reexpression on tumor growth. Recently, growing amount of evidence points out that p57 has a specific function in cell cycle regulation upon cellular stress that is only partially shared by the other CIP/KIP inhibitors p21 and p27. Furthermore, it is nowadays emerging that p57 plays a role in the induction of apoptosis and senescence after cellular stress independently of its cell cycle related functions. This review focuses on the contribution that p57 holds in regulating cell cycle arrest, apoptosis, and senescence after cellular stress with particular attention to the response of cancer cells.

Nutrient stress alters the glycosylation status of LGR5 resulting in reduced protein stability and membrane localisation in colorectal tumour cells: implications for targeting cancer stem cells

BACKGROUND

LGR5 is an important marker of intestinal stem cells and performs its vital functions at the cell membrane. Despite the importance of LGR5 to both normal and cancer stem cell biology, it is not known how microenvironmental stress affects the expression and subcellular distribution of the protein.

METHODS

Nutrient stress was induced through glucose starvation. Glycosylation status was assessed using endoglycosidase or tunicamycin treatment. Flow cytometry and confocal microscopy were used to assess subcellular distribution of LGR5.

RESULTS

Glucose deprivation altered the glycosylation status of LGR5 resulting in reduced protein stability and cell surface expression. Furthermore, inhibiting LGR5 glycosylation resulted in depleted surface expression and reduced localisation in the cis-Golgi network.

CONCLUSIONS

Nutrient stress within a tumour microenvironment has the capacity to alter LGR5 protein stability and membrane localisation through modulation of LGR5 glycosylation status. As LGR5 surface localisation is required for enhanced Wnt signalling, this is the first report to show a mechanism by which the microenvironment could affect LGR5 function.

Cancer stemness in Apc- vs. Apc/KRAS-driven intestinal tumorigenesis

Constitutive activation of the Wnt pathway leads to adenoma formation, an obligatory step towards intestinal cancer. In view of the established role of Wnt in regulating stemness, we attempted the isolation of cancer stem cells (CSCs) from Apc- and Apc/KRAS-mutant intestinal tumours. Whereas CSCs are present in Apc/KRAS tumours, they appear to be very rare (<10⁻⁶) in the Apc–mutant adenomas. In contrast, the Lin⁻CD24^hiCD29⁺ subpopulation of adenocarcinoma cells appear to be enriched in CSCs with increased levels of active β-catenin. Expression profiling analysis of the CSC-enriched subpopulation confirmed their enhanced Wnt activity and revealed additional differential expression of other signalling pathways, growth factor binding proteins, and extracellular matrix components. As expected, genes characteristic of the Paneth cell lineage (e.g. defensins) are co-expressed together with stem cell genes (e.g. Lgr5) within the CSC-enriched subpopulation. This is of interest as it may indicate a cancer stem cell niche role for tumor-derived Paneth-like cells, similar to their role in supporting Lgr5⁺ stem cells in the normal intestinal crypt. Overall, our results indicate that oncogenic KRAS activation in Apc-driven tumours results in the expansion of the CSCs compartment by increasing ®-catenin intracellular stabilization.

LGR5 promotes survival in human colorectal adenoma cells and is upregulated by PGE2: implications for targeting adenoma stem cells with NSAIDs

Cyclooxygenase-2 is overexpressed in the majority of colorectal tumours leading to elevated levels of prostaglandin E2 (PGE2), promoting many hallmarks of cancer. Importantly, PGE2 is reported to enhance Wnt/β-catenin signalling in colorectal carcinoma cells and in normal haematopoietic stem cells where it promotes stem cell function. Although Wnt signalling plays a crucial role in intestinal stem cells, the relationship between PGE2 and intestinal stem cells is unclear. Given that the key intestinal cancer stem cell marker LGR5 (leucine-rich G-protein coupled receptor 5) is a Wnt target and PGE2 enhances Wnt signalling, the focus of this study was to investigate whether PGE2 regulated LGR5 expression in colorectal adenoma cells and whether LGR5 was important for tumour cell survival. PGE2 upregulated LGR5 protein in adenoma (RG/C2) and carcinoma (DLD-1) cell lines. LGR5 knockdown induced cell death in RG/C2 and AA/C1 adenoma cells, suggesting that LGR5 has an important survival-promoting role in adenoma cells. Indeed, we detected LGR5 protein expression in 4 of 4 human adenoma cell lines. Furthermore, LGR5 small interfering RNA inhibited the survival-promoting effects of PGE2 in RG/C2, suggesting that PGE2 promotes adenoma cell survival, at least in part, by increasing LGR5 expression. These studies, therefore, show the first link between PGE2 and LGR5 in human colorectal adenoma and carcinoma cells and demonstrate a survival-promoting role of LGR5. As non-steroidal anti-inflammatory drugs (NSAIDs) cause adenomas to regress in FAP patients, these studies could have important implications for the mechanism by which NSAIDs are chemopreventive, as lowering PGE2 levels could reduce LGR5 expression and survival of LGR5(+) adenoma stem cells.

Effect of Multiple Irradiation with Low Doses of Gamma-rays on Morphological Transformation and Growth Ability of Human Embryo Cellsin Vitro

We have measured expression of transformed phenotypes in human embryo (HE) cells repeatedly irradiated with a dose of 7.5 cGy per week throughout the life span of these cells in vitro. Irradiation was repeated until the cells had accumulated 195 cGy at which time the cells had reached the equivalent of their 26th passage and samples of cells at several passages were assayed for cell survival by colony formation, for mutation at hypoxanthine guanine phosphoribosyl transferase (HGPRT) locus and for transformation by focus formation. The lifespan (mean population doublings) of multiple irradiated cultures with a total dose of 97.5 cGy was slightly, but significantly, prolonged over that of controls. For example, if cells had accumulated 195 cGy, the maximum number of cell division of HE cells in vitro extended to 130-160% of non-irradiated control. Although transformed foci were not observed with cells until cells had accumulated 97.5 cGy, it increased with increasing accumulated dose. No cells, however, showed unlimited life span in vitro and also expressed tumorigenicity.

VEGF 165 b, an antiangiogenic VEGF-A isoform, binds and inhibits bevacizumab treatment in experimental colorectal carcinoma: balance of pro- and antiangiogenic VEGF-A isoforms has implications for therapy

Bevacizumab, an anti-vascular endothelial growth factor (VEGF-A) antibody, is used in metastatic colorectal carcinoma (CRC) treatment, but responses are unpredictable. Vascular endothelial growth factor is alternatively spliced to form proangiogenic VEGF₁₆₅ and antiangiogenic VEGF₁₆₅b. Using isoform-specific enzyme-linked immunosorbent assay and quantitative polymerase chain reaction, we found that over 90% of the VEGF in normal colonic tissue was VEGF_xxxb, but there was a variable upregulation of VEGF_xxx and downregulation of VEGF_xxxb in paired human CRC samples. Furthermore, cultured colonic adenoma cells expressed predominantly VEGF_xxxb, whereas colonic carcinoma cells expressed predominantly VEGF_xxx. However, adenoma cells exposed to hypoxia switched their expression from predominantly VEGF_xxxb to predominantly VEGF_xxx. VEGF₁₆₅b overexpression in LS174t colon cancer cells inhibited colon carcinoma growth in mouse xenograft models. Western blotting and surface plasmon resonance showed that VEGF₁₆₅b bound to bevacizumab with similar affinity as VEGF₁₆₅. However, although bevacizumab effectively inhibited the rapid growth of colon carcinomas expressing VEGF₁₆₅, it did not affect the slower growth of tumours from colonic carcinoma cells expressing VEGF₁₆₅b. Both bevacizumab and anti-VEGF₁₆₅b-specific antibodies were cytotoxic to colonic epithelial cells, but less so to colonic carcinoma cells. These results show that the balance of antiangiogenic to proangiogenic isoforms switches to a variable extent in CRC, regulates tumour growth rates and affects the sensitivity of tumours to bevacizumab by competitive binding. Together with the identification of an autocrine cytoprotective role for VEGF₁₆₅b in colonic epithelial cells, these results indicate that bevacizumab treatment of human CRC may depend upon this balance of VEGF isoforms.

Increased sensitivity to TRAIL-induced apoptosis occurs during the adenoma to carcinoma transition of colorectal carcinogenesis

The death ligand TRAIL (Apo2L) has potential for cancer therapy, since tumour cells are thought to be more sensitive than normal cells. We investigated whether sensitivity to TRAIL increases during the adenoma to carcinoma transition of colorectal carcinogenesis. Under the same culture conditions, we compared the extent of TRAIL-induced apoptosis in four premalignant adenoma and three carcinoma cell lines. Although TRAIL induced some apoptosis in adenoma cultures, the carcinoma cell lines were significantly more sensitive (P<0.001). This finding was recapitulated in an in vitro model of tumour progression in which conversion of the adenoma cell line AA/C1 to a tumorigenic phenotype was associated with increased TRAIL sensitivity (P<0.001). Increased TRAIL sensitivity during colorectal carcinogenesis has been previously attributed to changes in the balance between TRAIL receptors TRAIL-R1 and -R2 and ‘decoy’ receptors TRAIL-R3 and -R4 during malignant progression. To address this, cell surface receptor expression was measured by flow cytometry. In summary, during colorectal carcinogenesis, there is a marked increase in sensitivity to TRAIL-induced apoptosis associated with progression from benign to malignant tumour that could be exploited for colon cancer therapy, but alterations in cell surface TRAIL receptor expression may not be the primary reason for this change.

Replicative senescence in normal liver, chronic hepatitis C, and hepatocellular carcinomas

There is growing evidence that senescent cells accumulate in vivo and are associated with the aging process in parallel with the progressive erosion of telomeres. Because recent data show that telomere shortening is involved in the pathogenesis of liver cirrhosis, we looked for replicative senescence cells in normal livers, chronic hepatitis C, and hepatocellular carcinoma (HCC). Replicative senescent cells were detected on liver tissue cryosections using expression of a specific marker, senescence-associated beta-galactosidase, a cytoplasmic enzyme detected at pH 6. A total of 57 frozen liver samples (15 normal liver, 32 chronic hepatitis C, and 10 HCCs) were studied. Replicative senescence was graded as absent in 56% of cases (32 of 57) and present in 44% (25 of 57). Replicative senescence was considered present in 3 of 15 normal livers (20%), 16 of 32 chronic hepatitis cases (50%), and 6 of 10 HCCs (60%). In the group of nontumoral livers, the presence of senescent cells in liver was associated with older age (P =.03). In the group with chronic hepatitis C, fibrosis stage, but not activity grade, was significantly correlated with the accumulation of replicative senescent cells (P <.001). Finally, beta-Gal staining in nontumoral tissue was strongly correlated with the presence of HCC in the surrounding liver (P <.001). These results suggest that chronic hepatitis C represents a relevant model of accelerated replicative senescence and that accumulation of replicative senescent cells predispose to HCC development. Detection of replicative senescent cells may then serve as a predictive marker of a hepatocellular carcinoma in the surrounding tissue. HUM PATHOL 32:327-332.

Deregulated expression of homeobox-containing genes, HOXB6, B8, C8, C9, and Cdx-1, in human colon cancer cell lines

Previously we have demonstrated a reciprocal deregulation of various homeobox genes (HOXB6, B8, C8 and C9 vs Cdx-1) in human colorectal cancer (CRC). In the present study, using RT-PCR, we have investigated the expression pattern of these homeobox genes in various human colon cell lines, representing various stages of colon cancer progression and differentiation. Thus, we have tested polyposis coli Pc/AA adenoma cells, Caco-2, HT-29 and LS174T adenocarcinoma cell lines. All cell lines, except LS174T, demonstrated a pattern of deregulated homeobox gene expression which resembled that of CRC. In contrast, the pattern of expression of these genes in the highly oncogenic LS174T cells, as well as in Caco-2 cells transfected with activated Ha-ras or Polyoma middle T oncogene, resembled that of the normal mucosa. The reciprocal deregulation of HOX and Cdx-1 genes in CRC and in CRC-derived cell lines suggests a possible role in human CRC development.

Cellular senescence and cancer

The proliferative lifespan of normal mammalian cells is limited by intrinsic controls, which desensitize the cell-cycle machinery to extrinsic stimulation after a given number of cell divisions. One underlying clock driving this process of 'replicative senescence' is the progressive erosion of chromosome telomeres, which occurs with each round of DNA replication. This appears to trigger growth inhibition via activation of the tumour suppressor gene (TSG) product, p53, and the consequent up-regulation of the cell-cycle inhibitor p21WAF1. Other inhibitory pathways are also activated (possibly by additional clocks), including the TSG p16INK4a and the less well-defined complementation group genes. Loss of one pathway can be compensated, after a limited extension of lifespan, by further up-regulation of the others, so that to escape mortality a developing tumour must overcome multiple 'proliferative lifespan barriers' (PLBs) by successive genetic events, each conferring a new wave of clonal expansion. This provides one explanation for the existence of multiple genetic abnormalities in human cancers; furthermore, the diversity in the nature and timing of these PLBs between different cell types may explain the variation in the spectrum of abnormalities observed between the corresponding cancers. Even if all senescence pathways are inactivated, immortalization can only be achieved if erosion of telomeres is halted, before their end-protecting function is lost. This usually requires either activation of telomerase during tumour development, if the cell of origin is telomerase-negative, or up-regulation if the normal cell already has some activity, but not enough to prevent erosion. In either case, cancers often maintain near-critical telomere lengths; hence pharmacological inhibition of telomerase remains an attractive approach to the selective killing of tumour cells.

Identification of BTG2, an antiproliferative p53-dependent component of the DNA damage cellular response pathway

Cell cycle regulation is critical for maintenance of genome integrity. A prominent factor that guarantees genomic stability of cells is p53 (ref. 1). The P53 gene encodes a transcription factor that has a role as a tumour suppressor. Identification of p53-target genes should provide greater insight into the molecular mechanisms that mediate the tumour suppressor activities of p53. The rodent Pc3/Tis21 gene was initially described as an immediate early gene induced by tumour promoters and growth factors in PC12 and Swiss 3T3 cells. It is expressed in a variety of cell and tissue types and encodes a remarkably labile protein. Pc3/Tis21 has a strong sequence similarity to the human antiproliferative BTG1 gene cloned from a chromosomal translocation of a B-cell chronic lymphocytic leukaemia. This similarity led us to speculate that BTG1 and the putative human homologue of Pc3/Tis21 (named BTG2) were members of a new family of genes involved in growth control and/or differentiation. This hypothesis was recently strengthened by the identification of a new antiproliferative protein, named TOB, which shares sequence similarity with BTG1 and PC3/TIS21 (ref. 7). Here, we cloned and localized the human BTG2 gene. We show that BTG2 expression is induced through a p53-dependent mechanism and that BTG2 function may be relevant to cell cycle control and cellular response to DNA damage.

Evidence for two senescence loci on human chromosome 1

Microcell-mediated introduction of a neo-tagged human chromosome 1 (HC-1-neo) into several immortal cell lines has previously been shown to induce growth arrest and phenotypic changes indicative of replicative senescence. Somatic cell hybridization studies have localized senescence activity for immortal hamster 10W-2 cells to a cytogenetically defined region between 1q23 and the q terminus. Previous microcell-mediated chromosome transfer experiments showed that a chromosome 1 with an interstitial q-arm deletion (del-1q) lacks senescence inducing activity for several immortal human cell lines that are sensitive to an intact HC-1-neo. In contrast, our studies reveal that the del-1q chromosome retains activity for 10W-2 cells, indicating that there are at least two senescence genes on human chromosome 1. Sequence-tagged site (STS) content analysis revealed that the q arm of the del-1q chromosome has an interstitial deletion of approximately 63 centimorgans (cM), between the proximal STS marker DIS534 and distal marker DIS412, approximately 1q12 to 1q31. This deletion analysis provides a candidate region for one of the senescence genes on 1q. In addition, because this deletion region extends distally beyond 1q23, it localizes the region containing a second senescence gene to approximately 1q31-qter, between DIS422 and the q terminus. STS content analysis of a panel of 11 10W-2 microcell hybrid clones that escaped senescence identified 2 common regions of loss of 1q material below the distal breakpoint of del-1q. One region is flanked by markers DIS459 and ACTN2, and the second lies between markers WI-4683 and DIS1609, indicating that the distal 1q senescence gene(s) localizes within 1q42-43.

Establishment and characterization of a human colon cancer cell line, OUMS-23, from a patient with familial adenomatous polyposis

A human colon carcinoma cell line designated OUMS-23 has been established from metastatic pericardial fluid of a male familial adenomatous polyposis patient with colon cancer. Since 1984, the epithelial cells have been maintained in culture. Ultrastructural studies revealed the presence of numerous microvilli on the cell surface and desmosomes between the adjacent cells. The cells secreted carcinoembryonic antigen into the culture medium (15 ng/10(6) cells-1 24 h-1). The cells expressed heat-stable placental-type-like alkaline phosphatase, whereas the normal counterparts expressed tissue-unspecific alkaline phosphatase. Karyotypic analysis showed that the cell line was of human origin and that the chromosome number was broadly distributed between 53 and 118. Southern blot analysis of the APC gene revealed no abnormalities in OUMS-24 cells, while Northern blot analysis demonstrated that the expression of the gene was about one-half that of the normal human fibroblasts. No mutations at the "hot spots" of codons 12 and 61 of H-, K- and N-ras proto-oncogenes were detected in the cells. The cells could grow in soft agar at a cloning efficiency of 6.5%, and upon transplantation into nude mice the cells formed tumors, which were diagnosed as differentiated adenocarcinoma.

Establishment and characterization of a new, spontaneously immortalized, pancreatic ductal cell line from the Syrian golden hamster

Spontaneously immortal pancreatic cell lines are not available. By use of a defined culture medium, such a line (TAKA-1) was established from the Syrian golden hamster. Cytological, cytogenetic, molecular biological, enzymatic and receptor patterns as well as antigenicity were studied and were compared with those of the normal hamster pancreatic ductal cells in vivo. TAKA-1 cells grew exponentially in a monolayer on collagen gel in a defined medium but did not proliferate in soft agar. Ultrastructurally, the cells closely resembled the normal hamster pancreatic ductal cells. Similarities and dissimilarities were found between the normal ductal cells and TAKA-1 cells. Similarities included the presence of cytokeratin, carbonic anhydrase and some tumor-associated antigens. However, unlike the normal ductal cells, TAKA-1 cells expressed blood group A antigen and anti-vimentin, showed affinity to selected lectins, and an abnormality of chromosome 3, which is suggested to be associated with immortality. Moreover, unlike the hamster pancreatic ductal cancer cells but like the normal hamster pancreatic ductal cells, TAKA-1 cells did not have a c-Ki-ras mutation. EGF, TGF-alpha and secretin, but not CCK or GRP, bound to the TAKA-1 cells. TAKA-1 cells produced TGF-alpha, and their growth was stimulated by exogenous EGF in serum-free medium. This cell line presents a suitable model for biologic and pathologic study of the hamster pancreatic ductal cells in vitro.

Cellular immortality: a late event in the progression of human squamous cell carcinoma of the head and neck associated with p53 alteration and a high frequency of allele loss

Many human tumors contain variant cells that, unlike their normal counterparts, possess indefinite proliferative potential in vitro. However, little is known of the relevance of these immortal cells to human carcinomas in vivo. To investigate immortality in a human tumor system, we established cultures from different stages of head and neck squamous carcinoma (SCC-HN). All the neoplastic cultures were transformed because they showed very low cornification in surface or suspension culture and were partially or completely resistant to suspension-induced death. Immortal variants were not detected in premalignant erythroplakia cultures, but their frequency increased with tumor progression, indicating that immortality is a late event in carcinogenesis. Some late-stage carcinomas still produced senescent cultures, but, significantly, all recurrent tumors were immortal. Immortal but not senescent carcinoma cultures were associated with p53 dysfunction and a high frequency of allele loss, indicative of tumor suppressor gene inactivation. These results show that there are at least two classes of human SCC-HN that are phenotypically and genotypically distinct and that the pathological stage of a given tumor is not necessarily indicative of the kind of cells it contains.

Karyotypic characterization of colorectal adenocarcinomas

Cytogenetic analysis of short-term cultures from 52 primary colorectal adenocarcinomas revealed clonal chromosome aberrations in 45 tumors, whereas the remaining 7 had a normal karyotype. More than 1 abnormal clone was detected in 26 tumors; in 18 of them, the clones were cytogenetically unrelated. The modal chromosome number was near-diploid in 32 tumors and near-triploid to near-tetraploid in 13. Only numerical aberrations were identified in 13 carcinomas, only structural aberrations in 3, and 29 had both numerical and structural changes. The most common numerical abnormalities were, in order of decreasing frequency, gains of chromosomes 7, 13, 20, and Y and losses of chromosomes 18, Y, 14, and 15. The structural changes most often affected chromosomes 1, 17, 8, 7, and 13. The most frequently rearranged chromosome bands were, in order of decreasing frequency, 13q10, 17p10, 1p22, 8q10, 17p11, 7q11, 1p33, 7p22, 7q32, 12q24, 16p13, and 19p13. Frequently recurring aberrations affecting these bands were del(1)(p22), i(8)(q10), i(13)(q10), and add(17)(p11-13). The most common partial gains were from chromosome arms 8q, 13q, and 17q and the most common partial losses from chromosome arms 1p, 8p, 13p, and 17p. A correlation analysis between the karyotype and the clinicopathologic features in our total material, which consists of altogether 153 colorectal carcinomas, including 116 with an abnormal karyotype, showed a statistically significant association (P < 0.05) between the karyotype and tumor grade and site. Carcinomas with structural chromosome rearrangements were often poorly differentiated; well and moderately differentiated tumors often had only numerical aberrations or normal karyotypes. Abnormal karyotypes were more common in rectal carcinomas than in carcinomas situated higher up. Near-triploid to near-tetraploid karyotypes were more than twice as frequent in tumors of the distal colon as in those of the proximal colon and rectum. The cytogenetic data indicate that carcinomas located in the proximal colon and rectum, which often are near-diploid with simple numerical changes and cytogenetically unrelated clones, probably arise through different mechanisms than do tumors located in the distal colon, which more often have complex near-triploid to near-tetraploid karyotypes.

Correlation of cellular differentiation in human colorectal carcinoma and adenoma cell lines with metabolite profiles determined by 1H magnetic resonance spectroscopy

The aim was to determine whether proton magnetic resonance spectroscopy (MRS) could grade human colorectal cells of differing malignant potential. A cell model of tumour development and progression comprising 2 non-tumorigenic adenoma lines and 4 carcinoma lines of increasing tumorigenicity was chosen. A gradual reduction in cellular differentiation and an accumulation of genetic alterations from adenoma to carcinoma characterized the selected cell lines. One-dimensional and 2-dimensional MRS showed that reduced differentiation in the cell model correlated with an increase in the levels of lipid, metabolites, the glycosylation intermediate uridine diphospho-N-acetylglucosamine and cell-surface fucosylation. Mutations involving the K-ras, APC and DCC genes are present both in adenoma- and in carcinoma-derived lines in this model, but the first evidence of an abnormality in the p53 gene was concomitant with the cells' ability to grow as a tumour in athymic nude mice. This genetic change coincided with the detection, by MRS, of UDP-hexose (ribose moiety, 2D MRS cross peak between H2 at 4.38 ppm and HI at 5.99 ppm) and the appearance of an additional fucosyl resonance (cross peak between-CH3 at 1.41 and H5 at 4.30 ppm) in the least tumorigenic of the carcinoma cell lines. An increase in complexity of the fucosylation spectral pattern was observed with further cellular de-differentiation and increased tumorigenicity. Collectively these data support the existence of an adenoma-carcinoma sequence.

A gene involved in control of human cellular senescence on human chromosome 1q

Normal cells in culture exhibit limited division potential and have been used as a model for cellular senescence. In contrast, tumor-derived or carcinogen- or virus-transformed cells are capable of indefinite division. Fusion of normal human diploid fibroblasts with immortal human cells yielded hybrids having limited life spans, indicating that cellular senescence was dominant. Fusions of various immortal human cell lines with each other led to the identification of four complementation groups for indefinite division. The purpose of this study was to determine whether human chromosome 1 could complement the recessive immortal defect of human cell lines assigned to one of the four complementation groups. Using microcell fusion, we introduced a single normal human chromosome 1 into immortal human cell lines representing the complementation groups and determined that it caused loss of proliferative potential of an osteosarcoma-derived cell line (TE85), a cytomegalovirus-transformed lung fibroblast cell line (CMV-Mj-HEL-1), and a Ki-ras(+)-transformed derivative of TE85 (143B TK-), all of which were assigned to complementation group C. This chromosome 1 caused no change in proliferative potential of cell lines representing the other complementation groups. A derivative of human chromosome 1 that had lost most of the q arm by spontaneous deletion was unable to induce senescence in any of the immortal cell lines. This finding indicates that the q arm of human chromosome 1 carries a gene or set of genes which is altered in the cell lines assigned to complementation group C and is involved in the control of cellular senescence.

A gene involved in control of human cellular senescence on human chromosome 1q

Normal cells in culture exhibit limited division potential and have been used as a model for cellular senescence. In contrast, tumor-derived or carcinogen- or virus-transformed cells are capable of indefinite division. Fusion of normal human diploid fibroblasts with immortal human cells yielded hybrids having limited life spans, indicating that cellular senescence was dominant. Fusions of various immortal human cell lines with each other led to the identification of four complementation groups for indefinite division. The purpose of this study was to determine whether human chromosome 1 could complement the recessive immortal defect of human cell lines assigned to one of the four complementation groups. Using microcell fusion, we introduced a single normal human chromosome 1 into immortal human cell lines representing the complementation groups and determined that it caused loss of proliferative potential of an osteosarcoma-derived cell line (TE85), a cytomegalovirus-transformed lung fibroblast cell line (CMV-Mj-HEL-1), and a Ki-ras(+)-transformed derivative of TE85 (143B TK-), all of which were assigned to complementation group C. This chromosome 1 caused no change in proliferative potential of cell lines representing the other complementation groups. A derivative of human chromosome 1 that had lost most of the q arm by spontaneous deletion was unable to induce senescence in any of the immortal cell lines. This finding indicates that the q arm of human chromosome 1 carries a gene or set of genes which is altered in the cell lines assigned to complementation group C and is involved in the control of cellular senescence.

Genetic and molecular basis for cellular senescence

Normal human and rodent cells in culture exhibit a finite life span at the end of which they exhibit morphological changes and cease proliferating, a process termed cellular senescence or cellular aging. Many cancer cells differ from normal cells in that they do not senesce and have an indefinite life span in culture, suggesting that alterations relating to cellular senescence are involved in the neoplastic evolution of tumor cells. Recent experimental results strongly support a genetic basis for cellular senescence. Defects in the senescence program in transformed cells can be corrected by introduction of a specific chromosome from normal cells into the abnormal cells. Using this approach, possible senescence genes have been mapped to specific chromosomes. Cell cycle control genes that regulate entry into the DNA synthetic phase of the cell cycle must be altered in senescent cells. Recent findings suggest that phosphorylation of the retinoblastoma gene is altered in senescent cells. It is possible, but not yet proven, that aging at the cellular level contributes to the aging of the individual. Therefore, an understanding of cellular senescence at the genetic and molecular levels may provide new insights into both the cancer and aging processes.

A single human colonic adenoma cell line can be converted in vitro to both a colorectal adenocarcinoma and a mucinous carcinoma

In a previous study, using a chemical carcinogen, we converted in vitro a non-tumorigenic cell line derived from a human colorectal diploid adenoma, designated PC/AA, into a tumorigenic cell line which, when inoculated into athymic nude mice, produced progressively growing adenocarcinomas. We now report that continuous in vitro passage of the PC/AA adenoma cell line resulted in its spontaneous transformation to a mucinous carcinoma with a modal karyotype of 51, XY, +i(Iq), +8, +9, +13, +i(13q), -21, +mar. These studies show that a single adenoma can be converted along 2 independent pathways, giving rise to either a mucinous carcinoma or an adenocarcinoma, and provide further experimental evidence for the adenoma-carcinoma sequence. Cytogenetic changes which occur along both pathways to tumorigenicity include abnormalities of chromosome I and multiple copies of chromosome 13. These abnormalities may be important in tumour development and progression in colorectal carcinogenesis.

Chromosome 1 in human colorectal tumors. Cytogenetic research on structural changes and their significance

The significance of short and long arm anomalies of chromosome 1 was investigated in 55 colorectal tumors comprising 41 carcinomas and 14 adenomas. The tumors were at various stages of transformation from adenoma to carcinoma. Our investigation was prompted by the observation of a p32-pter deletion on the short arm of chromosome 1 in a case of benign tubulovillous adenoma with mild dysplasia, as well as by frequent reports that chromosome 1 is involved in many neoplastic processes. Long arm anomalies were found in seven of the 41 carcinomas, six of which were in stage B2, and short arm anomalies in ten carcinomas at various stages. Three of the adenomas exhibited chromosome 1 anomalies, which in one case comprised a 1p32-pter deletion only. Overall, short arm anomalies especially concerned the p32-36 region. These results suggest that the cytogenetic anomalies respectively located on the short and long arms of chromosome 1 should be considered separately. Damage to the long arm might constitute a late non-specific event, whereas damage to the p32-pter region of the short arm might be involved in triggering colorectal tumor development.

Use of fluorescent in situ hybridisation to confirm trisomy of chromosome region 1q32-qter as the sole karyotypic defect in a colon cancer cell line

The sole chromosome defect in a colon cancer cell line derived from a patient with inherited nonpolyposis colorectal cancer was karyotypically designated as 46,XY,-13,+der(13)t(1;13)(q32.1;p11) on the basis of banding homology. We have obtained molecular confirmation that the additional chromosome material is derived from chromosome region 1q32-qter by the use of a highly specific fluorescent in situ hybridisation technique on G-banded chromosomes and also by Southern hybridisation.

Possible involvement of chromosome 1 in in vitro immortalization: evidence from progression of a human adenoma-derived cell line in vitro

We have previously reported that continuous in vitro passage in the presence of 3T3 feeders of a non-tumorigenic adenoma-derived epithelial cell line, designated PC/AA, resulted in its becoming immortal. At early passage PC/AA was normal diploid, whereas every cell of PC/AA late passage had an isochromosome 1(q) which led us to suggest that abnormalities of chromosome 1 may be involved in tumour progression. We now report the isolation of a 3T3-feeder-independent variant of early-passage PC/AA, designated PC/AA/FI, which was immortal in vitro and remained non-tumorigenic. Each cell of PC/AA/FI again has an isochromosome 1(q), like the late-passage PC/AA. However, with PC/AA/FI it is the other chromosome 1 of the homologous pair which is involved in the formation of the isochromosome 1(q). This is possible to determine because of the polymorphic centromeric heterochromatin on chromosome 1 of the early-passage PC/AA. With the late-passage PC/AA (grown with 3T3 feeders) the homologue with the large C-band has given rise to an isochromosome 1(q) whereas with PC/AA/FI it is the other homologue with the smaller C-band which has given rise to this isochromosome. Both the immortal PC/AA/FI and the immortal PC/AA late passage, therefore, have independent abnormalities involving chromosome 1. These results indicate that chromosome 1 may be involved in in vitro immortalization.

Immunodetection of cathepsins B and L present in and secreted from human pre-malignant and malignant colorectal tumour cell lines

Pre-malignant and malignant human colorectal tumour epithelial cell lines both secreted precursor forms of the 2 cysteine proteinases, cathepsins B and L. The amount of proteinases secreted by these cell lines varied according to the cell density. Comparison at similar cell densities showed that the pre-malignant, adenoma-derived cell line (PC/AA) secreted as much, or more, of both cathepsin B and L precursors as did the malignant, carcinoma-derived cell line (PC/JW/FI). However, mature forms of cathepsins B and L were detected in the culture media of only the carcinoma-derived cell line, thus indicating that the invasive potential of a tumour may be related to its ability to process extracellularly the secreted precursor enzyme to a mature and consequently active enzyme, rather than to the amount of proteinase synthesized and/or secreted. Similar results were obtained using 2 other epithelium-derived tumour cell lines, HT/29 (carcinoma) and SP/AN (adenoma). Immunolocation studies showed that cathepsin B was lysosomal while cathepsin L appeared to have a distribution more consistent with a plasma membrane association. Purified human cathepsins B and L (mature form) were capable of solubilizing an isolated basement membrane matrix (bovine anterior lens capsule) in vitro, thus indicating that the secreted mature enzymes and the membrane-associated cathepsin L could potentially degrade basal laminae or sub-endothelial basement membranes in vivo.