SL12 murine T-lymphoma: a new model for tumor cell heterogeneity.

It has been observed that subclones from the spontaneous murine AKR/J T-lymphoma cell line SL12 with similar in vitro growth characteristics exhibit stable differences in tumorigenicity. The cell line is composed of at least three distinct cloned cell types that are highly, moderately, or poorly tumorigenic in syngeneic host animals. When healthy, young, syngeneic host animals were given iv injections with the same number of viable growth phase cells, each cloned cell type had a different tumor incidence, latent period, and pattern of tumor spread. The unusual stability of the cloned cell lines is shown by a similar incidence, latency, and spread of the tumors when studied after more than 1 year of continuous in vitro culture. The SL12 clones also differ in several phenotypic characteristics commonly used to classify thymocyte maturation, e.g., a) the expression of three of seven surface antigens examined, b) the cellular response to glucocorticoid hormone, and c) the expression of terminal deoxynucleotidyl transferase.

Genetic complexity of glucocorticoid-induced lysis of murine T-lymphoma cells.

Several well characterized murine T-lymphoma cell lines were used in somatic cell hybridization experiments to study the genetic regulation of glucocorticoid-induced lysis. Cell fusions were carried out among the SL12-derived cloned lines and between the W7 and SAK8 lines all of which have functional hormone receptors. These cell lines differ in their sensitivity to glucocorticoid-induced lysis. The resultant hybrids were characterized by their growth response to 1 microM dexamethasone, their hormone receptor content, their chromosome number, and the expression of surface antigens. Fusion of the hormone-sensitive W7 parent to a number of glucocorticoid-resistant cell lines resulted in hybrids which were of the sensitive phenotype. In contrast the fusion of another hormone-sensitive clone, SL12.4, with glucocorticoid-resistant SL12 clones or with SAK8 always resulted in hybrids resistant to glucocorticoid lysis. These results reveal a complex genetic regulation of the hormone response or the requirement for multiple gene activity in the mechanism for glucocorticoid-induced cell lysis.

Malignant otitis externa in AIDS patients: case report and review of the literature.

Malignant otitis externa is a necrotizing infection of the external ear canal and surrounding soft tissue and bone, usually caused by Pseudomonas aeruginosa. The infection classically occurs in diabetic patients, however recently, several patients with the acquired immunodeficiency syndrome (AIDS) have been reported to have malignant otitis externa. A patient with AIDS who had malignant otitis externa with skull base osteomyelitis is presented and reported cases in patients with AIDS are reviewed. Predisposing factors include immunologic abnormalities (notably neutropenia), dermatitis, medications, neoplasm, and iatrogenic procedures, e.g., ear lavage. Treatment of malignant otitis externa has traditionally included anti-pseudomonal cephalosporins/penicillins and aminoglycosides for prolonged durations. Recently, ciprofloxacin has been shown to be effective as an oral regimen. With the increasing number of patients with AIDS being seen in the outpatient clinics, the diagnosis of malignant otitis externa should be considered in any patient with persistent ear pain or otorrhea who does not respond to conventional treatment for external otitis.

Wasting syndrome in AIDS: pathophysiologic mechanisms and therapeutic approaches.

Wasting syndrome is a common complication of HIV infection and is marked by progressive weight loss and weakness, often associated with fever and diarrhea. The pathophysiologic mechanisms responsible for this syndrome are not well defined, but it is clear that this is a multifactorial process in which the relative contribution of individual etiologic factors vary among patients. Considerations include inadequate diet, malabsorptive phenomena, metabolic derangements, and cytokine activity. The onset of opportunistic infections is often accompanied by a hypermetabolic state characterized by progressive weight loss. Potential cytokines that may promote weight loss in AIDS patients include tumor necrosis factor, interleukin-1, interleukin-6, and alpha-interferon. At present there is no effective treatment. Multiple therapeutic methods, including enteral and parenteral alimentation, appetite stimulants, recombinant growth hormone, and cytokine modulators, are currently being explored.

Tumorigenicity of T lymphoma/T lymphoma hybrids and T lymphoma/normal cell hybrids.

Stable hybrids formed between clones of established murine T-cell lymphoma lines, and between lymphoma clones and normal spleen or thymus cells were examined for their tumorigenic properties by intravenous (i.v.) and intradermal (i.d.) inoculation into syngeneic AKR mice. Fusion parents consisted of T lymphoma clones of high and low tumorigenicity derived from the SL 12 cell line. In addition, normal spleen cells and thymocytes were fused with poorly tumorigenic T-lymphoma clones. Hybrids tested by i.v. inoculation of 10(6) cells to syngeneic hosts showed that fusion between the lymphoma cells resulted in hybrids which displayed the phenotype of the highly tumorigenic parent. Also, it was shown that fusion of poorly tumorigenic lymphoma cells with normal spleen cells resulted in hybrids with enhanced tumorigenicity. Fusion of poorly tumorigenic lymphoma cells with normal thymocytes resulted in hybrids with the highest tumorigenic potential. The pattern of spread for the tumor/tumor hybrid was that of the highly tumorigenic parent. Tumor spread patterns for the spleen/tumor hybrids were different from those of the thymocyte/tumor hybrids. Intradermal inoculation of 10(5) cells from tumor/spleen or tumor/thymocyte hybrids revealed differences in latent periods between parental and hybrid cells, the tumor/thymocyte hybrids having the shortest latent period. Surface marker studies and T-cell antigen receptor mRNA determinations in the tumor cell/normal cell hybrids indicated that the normal parent was a cell of immature phenotype. Therefore, high tumorigenicity is a dominant characteristic, and poorly tumorigenic but "immortal" T lymphoma cells can derive characteristics which increase their in vivo growth capacity from the putative immature normal cells with which they selectively fuse.