Colorectal cancer and the integrin family of cell adhesion receptors: current status and future directions.

Tumour progression is thought to be determined, at least in part, by the balance between available cell surface receptors and the nature of the surrounding extracellular matrix. The integrin family of transmembrane adhesion receptors involved in tumour cell-matrix interactions mediates cell adhesion, migration, and differentiation. Certain patterns of integrin receptor expression on normal and malignant colon epithelial cells are emerging, and it is now clear that integrins can also regulate such divergent processes as cell proliferation and programmed cell death in this tumour type. This implies that integrins are involved in signal transduction events within colon carcinoma cells consequent upon their adhesive interaction with matrix molecules. A better understanding of the mechanisms involved in these events may lead to useful therapeutic strategies in the management of this disease.

Surgical history of Crohn's disease in a well-defined population.

Since 1935, 42 of 103 residents of Olmsted County, Minnesota, identified as having Crohn's disease underwent one or more surgical procedures. The incidence and type of surgical intervention, distribution of disease, and risk of recurrent disease after surgery were analyzed. Follow-up extended to 32 years, with a median of 8.5 years. Thirty-six patients underwent at least one definitive resection; eight of these patients subsequently underwent a second definitive operation. The likelihood that any patient would undergo operation was greatest within the first year of diagnosis. The proportion of patients in whom recurrent disease developed after the first and second definitive resections was 50% and 37%, respectively. Approximately half the patients who experienced a recurrence underwent further surgery. The site of diseased bowel and sex were not factors specifically influencing recurrence rates. Patients 40 years of age and older who underwent surgery appeared to fare better with respect to recurrent disease than younger patients. Although our findings suggest cumulative risks of recurrent disease after definitive resection similar to those reported from larger population groups or major referral centers, the proportion of patients who underwent surgery during the natural history of their Crohn's disease was much less than generally reported. We conclude that operation for Crohn's disease is not inevitable and that evidence to the contrary may imply both a treatment and a referral bias.

Cell adhesion molecules and colon cancer.

There is a general consensus that cell-cell and cell-matrix interactions determine, at least in part, the behaviour of colon cancer. The biological mediators responsible for these interactions are cell adhesion molecules belonging to several major receptor families called integrins, cadherins, the immunoglobulin superfamily, hyaluronate receptors and mucins. Emerging data indicate that certain patterns of adhesion receptor expression are associated with more aggressive disease. The present review examines the role of each of the receptor families in the development and progression of large bowel cancer.

Human colon cancer and fibroblast cell lines cultured in and on collagen gels.

Collagen is the major constituent of the in vivo extracellular matrix environment and the ability of collagen substrates to support growth of cultured cells in vitro is well recognized. The aim of the present study was to examine in vitro proliferation and matrix-binding of cells obtained from a human colon fibroblast and four colon cancer cell lines cultured in a collagen matrix environment. In contrast to colon fibroblasts, colon cancer cell lines proliferated in this culture system and their proliferative capacities were dependent upon the collagen concentration and whether tumour cells were seeded on or in the collagen. Both laminin and fibronectin stimulated growth of one of the four colon cancer cell lines without an apparent increase in cell-matrix binding. The use of collagen matrices to culture tumour cells in vitro might facilitate identification of factors which regulate growth of an individual's colorectal cancer.

A collagen matrix microassay for use in tumour-stromal cell co-cultures.

A collagen matrix microassay technique is described in which separation of collagen layers permits independent assessment of the proliferative capacity of each of two discrete cell populations. The two cell types used in this study were an established colon cancer cell line and a normal colon fibroblast cell line cultured under serum-free conditions. The implications of this in vitro technique for studies of tumour-host cell interactions are discussed.

In vitro chemotherapy sensitivity testing of primary human colorectal carcinomas.

The cells obtained from 138 tumor samples taken from 135 patients with colorectal malignancies were cultured in vitro in a soft agar colony formation assay similar to that of Salmon and colleagues [1]. Significant colony formation occurred for 63 (51%) of evaluable tumor cultures, 53 of which were also tested against chemotherapeutic agents in vitro. The median number of drugs tested per tumor was 15. Using 70% inhibition of colony formation as the criterion for significant drug-induced cytotoxicity, only 3/53 (6%) of the tumors were noted to be sensitive to any drug. When colony counts generated by initially plated small tumor cell aggregates were taken into account, 8/40 (20%) of the tumors were noted to be sensitive in vitro to one or more agents. Because of the low rate of drug sensitivity found with this in vitro assay, its current role in the prospective assignment of chemotherapeutic treatment for patients with colorectal carcinoma is somewhat limited.

The role of colon fibroblasts in malignant large bowel obstruction--an experimental in vitro model.

The mechanism of bowel obstruction in colorectal cancer is likely to involve interactions between tumour cells, host fibroblasts and the extracellular matrix. The role of fibroblast-mediated matrix reorganisation in malignant structures of the large bowel was examined in an in vitro collagen matrix model in which tumour cells and fibroblasts were cultured under serum-free conditions. Colon cancer cells secreted a factor(s) which enhanced the ability of colon fibroblasts to contrast a collagen matrix without an associated mitogenic response by the fibroblasts. Within uncontracted collagen gels marked elongation of fibroblast cell processes was observed in the presence of the tumour-derived factor(s). We propose that matrix reorganisation by host fibroblasts in the wall of the human colon is responsible, at least in part, for malignant large bowel obstruction.

Growth factor-induced proliferative responses of human and DMH-induced rat colorectal tumour cell lines.

The proliferative response of three human and three 1,2-dimethylhydrazine (DMH)-induced rat colon tumour cell lines to mouse epidermal growth factor (mEGF) and human urogastrone was examined in two in vitro assays (3H-thymidine uptake in liquid microculture and clonogenicity in semi-solid medium). In the 3H-thymidine uptake assay, one of three rat and one of three human colon tumour cell lines, i.e., r237 and LIM1215, were stimulated by mEGF. In the clonogenic assay, mEGF stimulated the one clonogenic rat tumour cell line r113, which did not respond in the 3H-thymidine uptake assay, and the human tumour cell line LIM1215. Urogastrone stimulated LIM1215 in both assay systems. The significance of these in vitro patterns of response to growth stimulatory factors is discussed.

In vitro chemotherapy sensitivity patterns of human colon carcinoma continuous cell lines.

The cells obtained from four established human colon carcinoma cell lines were cultured in soft agar in the presence of eight chemotherapeutic agents that have been used clinically in patients with metastatic colorectal carcinoma. 5-Fluorouracil, mitomycin C, adriamycin, and cis-platinum were highly cytotoxic in vitro at the concentrations employed. These findings were in marked contrast to in vitro chemotherapy sensitivity patterns previously reported by us for a large series of primary human colorectal carcinomas cultured in soft agar. The possible reasons behind these differences are discussed.

Nodal involvement in poorly differentiated breast cancer.

The degree of nodal involvement in a consecutive series of 400 patients with invasive ductal breast cancer is presented. A positive correlation was observed between the number of metastatic nodes identified and the number of axillary nodes examined for poorly but not moderately differentiated tumours. The relevance of this observation to breast cancer trials is discussed.

A re-examination of the molecular basis of cell movement.

A model for cell movement is presented. It is suggested that cells do not migrate on collagen using their VLA (very late antigen) integrins that bind this extracellular matrix protein. Rather, the cells utilize alpha v integrins to bind endogenously produced fibronectin, which binds to the underlying collagen. It is envisaged that cells proceed by a process of engagement and disengagement of alpha v integrins to the extracellular matrix, somewhat analogous to the motion of a monkey climbing a tree. Secretion of isoforms of the adhesion modulator, thrombospondin, regulates disengagement of the integrin from its ligand in migrating cells. The integrin disengagement signal is mediated by thrombospondin cross-linking the alpha v integrin to an integrin accessory molecule and thus activating protein kinases. The cross-linked receptor complex undergoes recycling back along actin stress fibres, guided by the integrin beta-subunit. After endocytosis and protein sorting the alpha v integrin is transported back to the leading edge off migrating cells in vesicles guided by the tubulin-binding capabilities of an integrin accessory molecule. Direct attachment to collagen required for processes, such as matrix contraction, is mediated by VLA integrins which displace alpha v integrins from points of attachment during integrin recycling, possibly through an alpha v beta 1 intermediary receptor.

Cell aggregates in the soft agar "human tumour stem-cell assay".

We evaluated colony formation in soft agar by cells obtained after mechanical and/or enzymatic disaggregation of 455 malignant human tumours. Counting and assessment of cell colonies in the agar plates were done by inverted microscopy, computerized image analysis, and inspection of serial photomicrographs of the agar plates. Our results indicate that standard methods of tumour disaggregation did not usually produce single-cell suspensions and that aggregates of tumour cells varying greatly in size were placed in the agar. Most groupings of cells identified as colonies 1-3 weeks after plating arose from enlargement of preexisting aggregates of cells.

Three new rat colon tumour cell lines from 1,2-dimethylhydrazine induced adenocarcinomas: morphology, karyotype and clonogenicity.

Three different tumour cell lines (Per113, Per192, Per237) were established from colon adenocarcinomas induced by 1,2-dimethylhydrazine (DMH) inbred male Wistar/Wag rats. Each cell line had epithelial morphology and an abnormal karyotype. The three cell lines were clonogenic in semi-solid medium, but differed in growth factor response, culture characteristics and karyotype. Each cell line was stimulated differentially by epidermal growth factor (EGF) and bombesin in culture. Only Per192 would passage in vivo in athymic nude mice. Per 113 had modal chromosome number of 70 with multiple structural abnormalities; Per237 had 43 chromosomes with consistent trisomy of chromosome I; 20-25% of the cells in line Per192 were in the tetraploid range with multiple copies of chromosome I.

Changing trends in perforated peptic ulcer during the past 45 years.

Since 1944 there has been a dramatic change in the pattern of admissions for perforated peptic ulcer (PPU) to the Royal Newcastle Hospital, the main teaching hospital of the Hunter Region, Australia. Between 1944 and 1950, females accounted for 6% of all perforations; since then the proportion of females admitted with this complication has risen to 32%. Simultaneously, the modal age for PPU has shifted from the fifth to the seventh decade and the ratio of gastric to pyloroduodenal perforations has fallen from 1.1:1 to 0.6:1. No good explanation for this change in the natural history of PPU, also noted elsewhere, is evident.

Perforated peptic ulcer in the Hunter region: a review of 174 cases.

A review of 174 consecutive patients admitted with a diagnosis of perforated peptic ulcer to eight Hunter Region hospitals during 1979-86 is presented. Among the female admissions, the proportion of patients greater than 70 years of age was twice that in males. One-third of all perforations were in females who accounted for two-thirds of all perforated gastric ulcers. Multivariate analysis revealed that perforations located in the stomach and older age were both significant independent variables adversely affecting outcome following surgery. In contrast, shock at presentation and delay in operating were not statistically significant independent risk factors.

Integrin alpha(v)beta6-associated ERK2 mediates MMP-9 secretion in colon cancer cells.

There is general consensus that matrix metalloproteinases are involved in tumour progression. We show herein that inhibition of integrin alpha(v)beta6 expression in colon cancer cells suppresses MMP-9 secretion. This integrin-mediated event is dependent upon direct binding between the beta6 integrin subunit and extracellular signal-regulated kinase 2. Targetting either beta6 or its interaction with extracellular signal-regulated kinase in order to inhibit matrix metalloproteinase activity may offer a useful therapeutic approach in preventing growth and spread of colon cancer.

Feasibility of sigmoidoscopic screening for colorectal cancer in the Hunter Region.

The success of a cancer detection programme depends on the co-operation of the target population. The aim of this study was to identify factors which might influence those at average and at higher risk of developing colorectal cancer to undergo a sigmoidoscopic screening test if offered. This was addressed by means of a household survey of individuals aged 40 years and over. Overall consent to undergo screening approximated 45%. There was a significant relationship between agreement to sigmoidoscopy and each of the following: age, marital status, educational level attained, and a previous episode of rectal bleeding. Individuals who had undergone sigmoidoscopy in the past were less willing to have the test performed again. Although individuals with a family history of bowel cancer in first-degree relatives perceived themselves as being more likely to develop colorectal cancer, this had no apparent impact on their willingness to have the test. The implications of these findings for community education programmes directed at colorectal cancer are discussed.

Arg-Gly-Asp-containing peptides expose novel collagen receptors on fibroblasts: implications for wound healing.

Integrins are a family of cell-surface receptors intimately involved in the interactions of cells with their extracellular matrix. These receptors comprise an alpha and beta subunit in noncovalent association and many have been shown to recognize and bind an arginine-glycine-aspartate (RGD) sequence contained within their specific extracellular matrix ligand. Fibroblasts express integrin receptors belonging to two major subfamilies. Some of the members within the subfamily defined by beta 1 (VLA) are receptors for collagen but, perhaps surprisingly, the other major subfamily of integrins on fibroblasts--that defined by the alpha chain of the vitronectin receptor, alpha v--all appear to bind primarily vitronectin and/or fibronectin. In the present study we show that RGD-containing peptides expose cryptic binding sites on the alpha v-associated integrins enabling them to function as collagen receptors. The addition of RGD-containing peptides to fibroblasts cultured on type I collagen induced dramatic cell elongation and, when the cells were contained within collagen matrices, the peptides induced marked contraction of the gels. These processes were inhibited by Fab fragments of a monoclonal antibody against an alpha v integrin. Also, alpha v-associated integrins from cell lysates bound to collagen I affinity columns in the presence, but not in the absence, of RGD-containing peptides. These data suggest a novel regulatory control for integrin function. In addition, because the cryptic collagen receptors were shown to be implicated in the contraction of collagen gels, the generation of such binding forces suggests that this may be the major biological role for these integrins in processes such as wound healing.