Oncogene-mediated transformation. An in vitro model for colon carcinogenesis.

Evaluation of molecular events in human colon polyps and tumors has revealed constitutive elevated expression of c-myc, activation of both ras and src proto-oncogenes, and allelic deletion events involving inactivation of putative regulatory genes, including p53. To evaluate the contribution of each of these events to colon carcinogenesis, it is desirable to establish epithelial cell lines representing different stages of neoplastic progression. Such in vitro models can be used to establish a primary role for different genes implicated in neoplastic transformation, identifying events involved in multistep carcinogenesis and delineating the factors modulating cellular transformation. We present herein a summary of such an in vitro model for colon carcinogenesis using the introduction of relevant genetic elements into normal mucosa to identify the molecular steps and accompanying cellular events underlying neoplastic progression in the colon.

Animal models for colon carcinogenesis.

Recent identification of genetic alterations in colon polyps and tumors has allowed construction of a hypothesis for the molecular basis of colon carcinogenesis. The consistency of observed genetic changes has inspired enthusiastic anticipation of new diagnostic tools and interventions for colon cancer. Appropriate animal models are crucial to the testing of molecular postulates as well as the development of markers and therapies for colon carcinogenesis. We discuss herein the various animal models that are currently used for the study of colon cancer as well as those that hold promise for the future. The contributions, drawbacks, and potential uses for the chemical carcinogen model, the multiple intestinal neoplasia model, transgenic animals, and the reconstruction model in the study of colon carcinoma are presented.

Predicting hospital charges for trauma care.

Diagnosis related groups (DRGs) have sharply decreased the amount of compensation hospitals can expect for providing trauma care. A total of 637 patients admitted for acute traumatic injuries between Oct 1, 1985, and July 30, 1986, had their DRG classifications, Injury Severity Scores, trauma scores, and ages compared with hospital charges in an attempt to identify factors that could be used to accurately predict hospital charges. The best prediction of charges was obtained when DRG assignment was combined with Injury Severity Scores and age. When the equation obtained by this approach was applied to a separate population of 301 patients, the average difference between the actual charge and that predicted was $38 and would have led to a 33-fold decrease in money lost by the hospital. Altering the DRG payment schedule as proposed would allow hospitals to be fairly compensated for the care of trauma patients.

The epidemiologic features of nosocomial infections in patients with trauma.

Sepsis is a major cause of morbidity and mortality in patients with trauma. To elucidate factors that might lead to infection, we studied the epidemiologic characteristics of nosocomial infections in our patient population with trauma. During a 3.5-year period, 2496 patients were entered into our hospital trauma registry and cross-matched with hospital infection control surveillance information. Two hundred twenty-nine patients with trauma and nosocomial infections were identified (9.2%), a figure that was nearly twice the nosocomial infection rate for the general hospital population. The majority of those infected were either orthopedic (51%), general surgical (25%), or neurosurgical (13%) patients. The most common sites of first infection were urinary tract (61%) or respiratory system (14%). Patients developing nosocomial infections were significantly older and had a higher Injury Severity Score than those who did not. Injury site was related to risk of infection with injuries of the spine, chest, and extremity showing the most significant relationship. The length of stay as well as hospital charges were significantly related to the occurrence of infectious complications. By determining the patient with trauma at risk for infection, treatment strategies can be designed to minimize septic complications.

Decreasing the incidence of surgical wound infections. Validation of a surveillance-notification program.

In an attempt to validate the observations of a previously published ten-year study of surgical wounds, we studied 8,474 wounds over an 18-month period using a protocol nearly identical to that of the previous study. Our study corroborated the following predictors of clean-wound infection: increasing duration of surgery, age less than 1 or greater than 50 years, increasing duration of preoperative hospitalization, use of drains, and shaving and emergency surgery. We failed to corroborate use of wound irrigation as a protective measure or time of preoperative shaving as a significant variable. Most importantly, we found a 42% reduction in the clean-wound infection rate during the study period (1.9% to 1.1%), adding support to the concept that a wound surveillance program with surgeon notification is both efficacious and cost-effective.

Intoxication and injury.

The relationship between alcohol use and injury severity was investigated in trauma patients admitted to a tertiary referral hospital during a 23-month period. Admission blood alcohol levels (BALs) were obtained on 427 trauma patients, who were stratified into three groups: those with no measurable blood alcohol, those within the legal limit of 100 mg/dL, and those over the legal limit or intoxicated. The no-alcohol group had significantly lower injury severity than the other two groups (p less than 0.001). Even when the BAL was well within the legal limit, injuries suffered by those in the alcohol-positive groups were more severe than those in the no-alcohol group. Confirmatory evidence of the effect of alcohol on injury severity was reflected by a 2.3% mortality in alcohol-negative patients compared with a 13.3% death rate in alcohol-positive patients (p less than 0.0001). To assess the potentially confounding effect of alcohol on injury scoring accuracy, we examined the change in Glasgow Coma Scale (GCS) scores following admission. No significant differences were found when admission GCS values were compared with GCS determinations made 24 hours following admission by separate observers. To correct for any potential bias as a tertiary referral center, repeat analysis with exclusion of transferred patients was done with essentially no change in results. Our data revealed a highly significant relationship between alcohol use, degree of injury, and resource consumption.

Immortalization and neoplastic transformation of normal rat colon epithelium: an in vitro model of colonic neoplastic progression.

BACKGROUND: Because of the refractory nature of colon epithelium to growth and maintenance in vitro, the cell lines currently available for study are derived from tumors. Unlike most epithelial model systems, there exist no preneoplastic, nontumorigenic colon cell lines for manipulation and study. METHODS: Intact fetal rat colon was cultured in the presence of a feeder layer of cells producing a retrovirus that harbors the SV40 LT gene resulting in the establishment of immortalized colon cell lines. RESULTS: The epithelial and intestinal origin of cell lines was established from the constitutive expression of keratin and villin, respectively. All cell lines displayed an absence of anchorage independent growth and failed to produce tumors in vivo. Neoplastic transformation of immortalized rat colon epithelial cell lines was achieved following introduction of individual oncogenic ras gene members or the v-src oncogene. Probing of cell lysates with phosphotyrosine antibodies revealed altered phosphotyrosyl protein profiles associated with different stages of colonic neoplastic progression. CONCLUSIONS: The establishment of immortalized nontumorigenic colon epithelial cell lines facilitates the biochemical analysis of events associated with different stages of colonic neoplastic progression. In addition, this simple culture technique lends itself to studies involving alternative genetic elements implicated in the genesis of colon tumors.

Practical evaluation of trauma deaths.

The TRISS method of auditing trauma deaths necessitates audit of patients with minor injuries who die of their underlying medical problems. Using an anatomic definition of injury as a criterion for audit, as suggested by Wesson et al. at the Hospital for Sick Children in Toronto, excludes patients with minor injuries but necessitates audit of patients who expired due to systems problems rather than in-hospital patient care. We propose combining the TRISS and Toronto methods in order to identify the deaths truly appropriate for detailed review of hospital care. Fifty-four trauma deaths over a 22-month period were audited and categorized as frankly preventable, potentially salvageable, or nonpreventable. Considering only in-hospital care, the deaths designated as potentially salvageable by audit were likely to be identified by both TRISS and Toronto, while deaths targeted by only one system were more likely to be nonpreventable by audit. The predictive value of this combination of methods (84.6%) was better than Toronto (52.4%) or TRISS (54.5%) using audit results as the standard for comparison. This simple computerized method may serve as a practical and inexpensive method of targeting deaths for in-depth review.

Overexpression of pp60c-src elicits invasive behavior in rat colon epithelial cells.

BACKGROUND & AIMS: Src activation is reported as an early event found in preneoplastic colonic adenomas and in 70% of colon carcinomas. The aim of this study was to identify the biological consequences of c-src overexpression in rat colon epithelial cells. METHODS: Introduction and overexpression of c-src in an immortalized rat colon epithelial cell line was achieved using lipofection. Transfectants were tested for changes in growth and cell behavior using different in vitro assay systems. RESULTS: Colon epithelial cells overexpressing c-src showed the ability to form microcolonies in soft agar without acquiring tumorigenic potential. In in vitro assays, c-src transfectants displayed a gain of invasive potential through Matrigel without an accompanying change in migrational ability. No discernible qualitative changes were observed in the phosphotyrosyl protein profile between c-src and v-src transfectants. Assessment of the cadherin/catenin status in these cells revealed an intact, functional complex with no detectable tyrosine phosphorylation of different components of the complex. CONCLUSIONS: Overexpression of c-src in an immortalized rat colon epithelial cell line does not elicit full neoplastic transformation but enhances anchorage-independent growth and confers invasion capability. Increased invasion through Matrigel was not linked to inactivation of the cadherin complex in c-src transfectants.