Allelotype analysis of mouse lung carcinomas reveals frequent allelic losses on chromosome 4 and an association between allelic imbalances on chromosome 6 and K-ras activation.

We generated allelotypes of 38 methylene chloride-induced lung carcinomas from female C57BL/6J x C3H/6J F1 (hereafter called B6C3F1) mice. Two or more polymorphic markers per autosome, most of them microsatellites, were examined for loss of heterozygosity. Allelic losses throughout the genome were generally infrequent except for markers on chromosome 4, which were lost in approximately one-half of the carcinomas. Analysis of lung adenomas indicated that chromosome 4 loss was associated with malignant conversion. In addition, chromosome 4 loss were specific for lung carcinomas based on comparison to methylene chloride-induced liver tumors and additional studies of lung tumors from a variety of treatment protocols and different mouse strains. Preferential loss of the maternal chromosome 4 was observed in B6C3F1 carcinomas. Analyses of additional tumors induced in mice from two reciprocal crosses, A/J x C3H/HeJ F1 (hereafter called AC3F1) and C3H/HeJ x A/J F1 (hereafter called C3AF1), provided evidence for the inactivation of one allele of the putative chromosome 4 tumor suppressor gene by parental imprinting. Most B6C3F1 tumors lost all chromosome 4 markers examined, suggesting nondisjunction events. In contrast, several C3AF1 and AC3F1 tumors appeared to have interstitial deletions that defined the smallest region of overlap as a 9-cM interval between Ifa-2 and D4Nds2. The homologous region on human chromosome 9p21-22 is frequently lost in a variety of tumors including lung cancers. A candidate tumor suppressor gene, MTS1, is located in this region, which is homozygously deleted or mutated in cell lines derived from a variety of human tumors. Finally, an association between K-ras gene activation and allelic imbalances on chromosome 6 was observed for B6C3F1 lung tumors.

Splenic rupture in hemophilia.

PURPOSE: Little information is available regarding splenic injury in patients with hemophilia. We describe here the management of splenic rupture in five of our patients with hemophilia and summarize the literature describing this complication. PATIENTS AND METHODS: Two human immunodeficiency virus-seropositive patients were managed medically and did not require splenectomy. A third patient had a high titer inhibitor to both porcine and human factor VIII and required emergency splenectomy. Two boys had not been previously diagnosed with hemophilia until they underwent splenectomy after abdominal trauma. RESULTS: All five patients survived. CONCLUSIONS: These cases demonstrate that nonsurgical management of splenic injury in patients with hemophilia can be performed safely and that splenectomy can be successfully performed despite a high titer of factor VIII inhibitor.

Identification of genes associated with tumor suppression in Syrian hamster embryo cells.

Loss of a tumor-suppressor gene function appears to play a critical role in the multistep process of neoplastic transformation of Syrian hamster embryo (SHE) cells in vitro. Clonal variants of two independent, preneoplastic cell lines have been isolated that have either retained (termed supB+) or lost (termed supB-) the ability to suppress the tumorigenicity of a highly malignant benzo[alpha]pyrene-transformed SHE cell line (BP6T) in cell hybrids. We have pursued several approaches in an attempt to identify genes that are responsible for tumor suppression in these cells. The only consistent differences detected in two-dimensional gel analyses of supB+ and supB- cellular proteins were decreases in the levels of two high molecular weight isoforms of tropomyosin in supB- cells. Differential screening of a supB+ cDNA library for genes that are preferentially expressed in supB+ cells yielded cDNA clones for four genes, i.e., collagen type II, collagen type IX, H19, and a previously unidentified gene (clone 5). Nuclear run-on assays suggested that higher transcription rates were responsible for the increased steady-state levels of some of these transcripts in supB+ cells. DNA sequence comparisons showed that two copies of a 9 bp element, previously identified in each of the mouse H19 enhancers, were also present in the 5' flanking region of the rat type II collagen gene. A transcription factor that controls expression of the collagen and H19 genes through binding to this conserved motif would be an attractive candidate for the supB+ gene or at least a mediator of the supB+ phenotype.