Hybrids of aneuploid human cancer cells permit complementation of simple and complex cancer defects.

Causes for the complex phenotypes of cancers, such as altered differentiation, invasion and metastasis, are not known, and multigenic defects are likely. In contrast, well-defined deficiencies, such as those affecting DNA-repair mechanisms and enzymatic pathways, are simple, typically caused by one or a few gene mutations. Complementation by introducing defined genetic elements is used to study simple cancer phenotypes, while complementation by the fusion of whole cells is employed occasionally for complex ones.

Frequent mutations in the 3'-untranslated region of IFNGR1 lack functional impairment in microsatellite-unstable colorectal tumours.

Microsatellite repeats are frequently found to be mutated in microsatellite-instable colorectal tumours. This suggests that these mutations are important events during tumour development. We have observed frequent mutations in microsatellite-instable (MSI-H) tumours and cell lines of a conserved A14 repeat within the 3'-untranslated region of the interferon-gamma receptor 1 gene (IFNGR1).

High-throughput screening identifies novel agents eliciting hypersensitivity in Fanconi pathway-deficient cancer cells.

Inactivation of the Fanconi anemia (FA) pathway occurs in diverse human tumors among the general population and renders those tumors hypersensitive to DNA interstrand-cross-linking (ICL) agents. The identification of novel agents to which FA pathway-deficient cells were hypersensitive could provide new therapeutic opportunities and improve our molecular understanding of the FA genes. Using high-throughput screening, we assessed the growth of isogenic human cancer cells that differed only in the presence or absence of single FA genes upon treatment with 880 active drugs and 40,000 diverse compounds.

Targeted deletion of MKK4 in cancer cells: a detrimental phenotype manifests as decreased experimental metastasis and suggests a counterweight to the evolution of tumor-suppressor loss.

Tumor-suppressors have commanded attention due to the selection for their inactivating mutations in human tumors. However, relatively little is understood about the inverse, namely, that tumors do not select for a large proportion of seemingly favorable mutations in tumor-suppressor genes. This could be explained by a detrimental phenotype accruing in a cell type-specific manner to most cells experiencing a biallelic loss.

Theoretical proposal: allele dosage of MAP2K4/MKK4 could rationalize frequent 17p loss in diverse human cancers.

Although aneuploidy is a global genomic abnormality present in most human cancers, the clonal selection model best explains the action of select activating mutations in oncogenes and homozygous losses of tumor-suppressor genes. Simple gene dosage changes are difficult however, to incorporate into this model, in part due to negative feedback loops that govern major cancer mutational targets (e.g.

Identification of a 7.1-mega base pairs minimal deletion at 14q31.1-32.11 in adenocarcinomas of the gastroesophageal junction.

In a recent evaluation by comparative genomic hybridization, we demonstrated chromosome 14q31-32.1 to be frequently deleted in adenocarcinomas of the gastroesophageal junction. This suggests the presence of a tumor suppressor gene in the deleted region.

In vivo therapeutic responses contingent on Fanconi anemia/BRCA2 status of the tumor.

Purpose: BRCA2, FANCC, and FANCG gene mutations are present in a subset of pancreatic cancer. Defects in these genes could lead to hypersensitivity to interstrand cross-linkers in vivo and a more optimal treatment of pancreatic cancer patients based on the genetic profile of the tumor.

Experimental Design: Two retrovirally complemented pancreatic cancer cell lines having defects in the Fanconi anemia pathway, PL11 (FANCC-mutated) and Hs766T (FANCG-mutated), as well as several parental pancreatic cancer cell lines with or without mutations in the Fanconi anemia/BRCA2 pathway, were assayed for in vitro and in vivo sensitivities to various chemotherapeutic agents.

Functional defects in the fanconi anemia pathway in pancreatic cancer cells.

Biallelic BRCA2-mutations can cause Fanconi anemia and are found in approximately 7% of pancreatic cancers. Recently, several sequence changes in FANCC and FANCG were reported in pancreatic cancer. Functional defects in the Fanconi pathway can result in a marked hypersensitivity to interstrand crosslinking agents, such as mitomycin C.