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Biomedical subjects

A Hague

Publications and source records attributed to A Hague.

30 records · Page 2Linked to original sources
PubMed1994

Loss of APC protein expressed by human colonic epithelial cells and the appearance of a specific low-molecular-weight form is associated with apoptosis in vitro.

APC (adenomatous polyposis coli) protein is differentially expressed in the normal colonic crypt and believed to be involved in colonic cell maturation. In this work we investigated whether expression of the APC protein is associated with cell death in colonic epithelial cells. We have previously reported an in vitro system to study apoptosis. Briefly, cells attached to the flask have a low frequency of apoptosis (1-3%), whereas cells that detach from the flask and float in the medium have a high proportion of apoptotic cells (36-96% depending on the cell line). The full-length 300-kDa or truncated APC protein, normally expressed by the attached cells (detected using the FE9 antibody), was found to be lost in the floating apoptotic cells in 8/11 colon tumour cell lines examined. In addition, the APC antibody FE9 detected a 90-kDa protein in the floating apoptotic cells of all cell lines investigated, which was not present in attached cells. Furthermore, loss of full-length APC and gain of the 90-kDa protein was observed in the apoptotic cells of 2 cell lines derived from other tissues: the SV40-transformed fibroblast cell line CMSV40fib and the lymphoblastoid B-cell line BJA-B. In cells repeatedly frozen and thawed, believed to induce necrotic cell death, full-length or truncated APC was also lost, though a 95-kDa protein distinct from that in apoptotic cells was observed. Specific loss of full-length or truncated APC (resulting in a 90-kDa protein in apoptotic cells but a 95-kDa protein in necrotic cells) is therefore associated with cell death. Our findings suggest a possible role for APC in cell survival.

Adenoma↗
PubMed1994

BCL-2 expression in human colorectal adenomas and carcinomas.

As BCL-2 oncoprotein has been implicated as a survival factor in a number of tissues, we examined colorectal tumour specimens and cell lines for BCL-2 expression. BCL-2 protein was expressed in 19/22 adenocarcinomas and 12/13 adenomas. 6/9 carcinoma cell lines and 7/8 adenoma cell lines were also BCL-2 positive. BCL-2 expression was retained in metastases to the regional lymph nodes (3/3 specimens) and in the cell line SW620, derived from a lymph node metastasis. These studies suggest a role for BCL-2 in promoting cell survival of benign and malignant colorectal tumours and that BCL-2 deregulation may be a relatively early event in colorectal carcinogenesis. The retention of BCL-2 expression in the carcinomas and lymph node metastases may explain the resistance of colorectal tumours to chemotherapeutic treatment.

3T3 Cells↗
PubMed1993

Sodium butyrate induces apoptosis in human colonic tumour cell lines in a p53-independent pathway: implications for the possible role of dietary fibre in the prevention of large-bowel cancer.

The purpose of this study was to determine whether cultured colonic adenoma and carcinoma cells undergo apoptosis (programmed cell death) in vitro and whether specific growth and dietary factors, thought to be involved in the control of growth and differentiation of human colonic cells, could induce cell death through apoptosis. In cell lines originating from 6 colorectal adenomas and 7 carcinomas, spontaneous apoptosis was observed. Sodium butyrate, a naturally occurring fatty acid, is present in the human large bowel in millimolar amounts as a result of bacterial fermentation of dietary fibre. Sodium butyrate, at physiological concentrations, induced apoptosis in 2 adenoma cell lines, RG/C2 and AA/Cl, and in the carcinoma cell line PC/JW/FI. In contrast, transforming growth factor beta 1, which is thought to have an important role in the control of growth in colonic epithelium, did not induce apoptosis. Neither RG/C2 nor PC/JW/FI contain wild-type p53, therefore this tumour-suppressor gene is not required to mediate signals for the induction of apoptosis in colonic tumour cells. Our studies report the induction of apoptosis in colonic tumour cells by the naturally occurring fatty acid sodium butyrate. Since sodium butyrate is produced by bacterial fermentation of dietary fibre, the observation that this fatty acid can induce apoptosis could, in part, explain why a high-fibre diet appears to be protective against colon cancer. Escape from the induction of programmed cell death may be an important event in colorectal carcinogenesis.

Adenoma↗
PubMed1993

Escape from negative regulation of growth by transforming growth factor beta and from the induction of apoptosis by the dietary agent sodium butyrate may be important in colorectal carcinogenesis.

There are a number of lines of evidence suggesting that transforming growth factor beta (TGF beta) has an important role in the control of intestinal growth and differentiation. In vivo localization studies show that TGF beta expression occurs predominantly in the differentiated non proliferating cells of the intestinal epithelium. The use of an antisense expression vector for TGF beta resulted in an increased tumorigenicity in an antisense-transfected cancer cell line. In vitro proliferation studies showed colorectal premalignant adenoma cells to be more sensitive to the growth inhibitory effects of TGF beta than colorectal cancer cells. Furthermore the conversion of an adenoma to a carcinoma was accompanied by a reduced response to the inhibitory effects of TGF beta. The acquisition of partial or complete resistance to the inhibitory effects of TGF beta may be an important late event in colorectal carcinogenesis. Of further interest is the possibility that clonal selection could occur even more rapidly in colorectal tumour cells which not only had lost response to TGF beta inhibition but produced TGF beta and were growth stimulated by it. This could have the advantage of not only inhibiting the growth of surrounding less malignantly advanced cells but of also escaping from their potential growth suppressive influence. Carcinogenesis is not, however, simply losing response to negative regulators of growth; the fully malignant cell has to acquire new characteristics of invasiveness and metastatic potential. Growth factors including TGF beta may have a role in the complex cascade of events leading to the activation of proteolytic enzymes which are involved in progression to an invasive phenotype. Cell proliferation in the large bowel, as well as being under the control of endogenous growth factors, is also under the influence of dietary components in the lumen such as the naturally occurring fatty acid sodium butyrate. Sodium butyrate at physiological concentrations induces apoptosis (programmed cell death) in colonic tumour cell lines. Since sodium butyrate occurs naturally in the colorectum, being produced by bacterial fermentation of dietary fibre, it may be involved in the control of cell death in human colorectal epithelium. This could, in part, explain the apparent protective effects of dietary fibre. Clonal evolution and tumour progression in colorectal carcinogenesis could therefore involve loss of response to endogenous growth factors such as TGF beta and an escape from the induction of programmed cell death by dietary factors.

Apoptosis↗
PubMed1993

Biological consequences of the genetic changes which occur during human colorectal carcinogenesis.

Colorectal carcinogenesis is a complex multistage process and occurs through the accumulation of gene mutations in both oncogenes and tumour suppressor genes. Frequent genetic abnormalities include mutation of the familial adenomatous polyposis (APC) and/or the mutated in colorectal cancer (MCC) genes on chromosome 5q21, activation of K-ras and loss of the tumour suppressor genes p53 and DCC (deleted in colorectal cancer). In our laboratory we have developed human in vitro colonic cell culture model systems, to determine the biological consequences of these well characterised genetic changes, and how such changes can uncouple proliferation from differentiation and ultimately lead to the malignant phenotype.

Colorectal Neoplasms↗
PubMed1993

In vitro models of human colorectal cancer.

Epithelial cell lines that differentiate in vitro have been isolated from hereditary and sporadic colorectal adenomas representing different stages in tumour progression, from small adenomas with a low malignant potential to large adenomas with a relatively high malignant potential. The majority of cell cultures derived from small adenomas senesced, whereas the larger adenomas were more likely to give rise to an immortal cell line. Karyotypic analysis has shown that specific abnormalities of chromosomes 1, 6, 7, 13, 14, 17, 18 and 22 occur in these adenoma cell lines. Abnormalities of chromosome 1 have been implicated in tumour progression and the in vitro immortalization of colorectal adenomas. Molecular and cellular changes involving abnormalities of chromosomes 1 and 18, TP53 and ras gene mutations and reduced response to the growth inhibitory effects of TGFB and sodium butyrate, which occur during tumour progression, suggest that the in vitro model has relevance to in vivo carcinogenesis.

Adenoma↗
PubMed1992

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.

Adenocarcinoma↗
PubMed1990

A study of mitotic division fidelity and numerical chromosome changes in ageing Syrian hamster dermal cells.

Events associated with culture ageing in Syrian hamster dermal cells have been studied from the time of culture isolation during continuous passage until they senesced and died. Microscopic examination of mitotic cells using differential staining of chromosome and spindle apparatus assessed the faithfulness of cell division. Other indicators of the quality of cell division were obtained from chromosome counts, micronucleus frequencies and incidences of binucleate cells. A loss of spindle fidelity and an increase in aneuploidy corresponded to the period of culture senescence. The data presented indicate that the loss of division fidelity and chromosome number instability is an important indicator of the progression of a mammalian culture to senescence under in vitro conditions. Such information may provide the basis of a model for the study of factors which modify mitotic fidelity and senescence and provide a methodology for monitoring the suitability of mammalian cultures for commercial usage.

Animals↗
PubMedDate not supplied

Colorectal carcinogenesis: sequential steps in the in vitro immortalization and transformation of human colonic epithelial cells (review).

The development of colorectal cancer is an excellent example of the complex multistage nature of carcinogenesis and most colorectal cancers are thought to develop from adenomas. In this paper we have reviewed in vitro models developed in our laboratory for the study of human colorectal carcinogenesis. For these studies epithelial cell lines have been isolated from hereditary and sporadic colorectal adenomas representing different stages in tumour progression. Karyotypic analysis has shown specific abnormalities of chromosomes 1, 7, 14, 17, 18 and 22 to occur in these premalignant adenoma cell lines. The majority of cell cultures derived from small adenomas (less than 1 cm in diameter) senesced whereas the larger adenomas (greater than 2 cm in diameter) were more likely to give rise to immortal cell lines indicating that the acquisition of in vitro immortality occurs at a relatively late stage of colorectal carcinogenesis. Abnormalities of chromosome I have been implicated in tumour progression and in the in vitro immortalization of colorectal adenomas. Furthermore, several stages have been described in the transformation of an adenoma cell line PC/AA to a tumorigenic phenotype. Sodium butyrate and the potent carcinogen N-methyl-N-nitro-nitrosoguanidine (MNNG) were used in this transformation. Sodium butyrate is proposed to act as a possible promoter of colorectal carcinogenesis, and MNNG to cause the further genetic changes required for the conversion of the premalignant cells to a carcinoma. Markers to study the progression of an adenoma cell line to a tumorigenic phenotype in vitro include in vitro immortalization, aneuploidy, clonogenicity, resistance to the inhibitory effects of sodium butyrate, anchorage independent growth, ras gene activation, production of active proteinases and tumorigenicity in athymic nude mice. A role for a constitutively produced tumour promoter in colorectal carcinogenesis is discussed together with the possibility that different events are involved in the development of sporadic versus hereditary tumours due to the importance of the microenvironment in hereditary cancer. Our in vitro progression provides the first experimental evidence for the adenoma to carcinoma sequence and the cytogenetic evidence suggests that it is relevant to in vivo carcinogenesis.

Adenoma↗