A microsatellite within the MUC1 locus at 1q21 is altered in the neoplastic cells of breast cancer patients.

Paired DNA samples from the neoplastic and nonneoplastic cells of 118 patients with the sporadic, nonfamilial form of breast cancer were analyzed for evidence of genetic alteration at a polymorphic microsatellite mapped to intron 6 within the MUC1 gene at 1q21. Two other microsatellite loci, D1S104 and APO-A2, which also map to 1q21, were analyzed as well. The frequency of alteration at the microsatellite within the MUC1 locus was significantly higher than D1S104 or APO-A2 (P < 0.001). Analysis by Southern blotting of the VNTR region of the MUC1 gene revealed an amplification of one allele in 34 of 54 informative cases (63%). There was no significant association between these alterations and alterations of the microsatellite within the same locus, suggesting independent mechanisms were responsible for the genetic changes. Microsatellite loci D17S579 at 17q21, the site of the BRCA1 gene, and D18S34 at 18q21-qter, the deleted in colorectal cancer locus, were also analyzed by PCR. Alterations at D17S579 and D18S34 were detected in 18.8% and 6.2% of patients, respectively (P < 0.001, and P < 0.1 relative to the frequency of alteration at D1S104 or APO-A2). A previously described polymorphism of hMSH2 was altered in 16.4% of cases.

Interleukin-2-secreting mouse fibroblasts transfected with genomic DNA from murine neoplasms induce tumor-specific immune responses that prolong the lives of tumor-bearing mice.

Genetic alterations are a common feature of the malignant phenotype. Among other properties, altered genes may be responsible for invasion and metastasis, as well as for resistance to chemotherapeutic agents. Under appropriate circumstances, the products of other altered genes expressed by malignant cells may act as tumor-associated T-cell epitopes, capable of provoking antitumor immune responses. As a novel means of augmenting the immunogenicity of the gene products, unfractionated, sheared genomic DNA from various tumor cell lines (B16F1 melanoma, B16F10 melanoma, MOPC-315 plasmacytoma, C1498 lymphoma, or J558 myeloma), or from non-neoplastic liver cells of tumor-free mice, was transfected into LM cells, a mouse fibroblast cell-line (H-2k) that had been modified previously by retroviral gene transfer to secrete interleukin-2 (IL-2). The IL-2-secreting transfected cell populations were then tested for their immunogenic properties toward B16F1 (H-2b) or C1498 (H-2b) cells in syngeneic C57BL/6 mice. The antitumor responses were specific for the type of tumor from which the DNA was obtained. The survival of C57BL/6 mice injected with a mixture of viable B16F1 cells and IL-2-secreting LM cells transfected with DNA from B16F1 cells was significantly prolonged. In a similar manner, the survival of C57BL/6 mice injected with a mixture of C1498 cells and IL-2-secreting LM cells transfected with DNA from C1498 cells was prolonged as well. The immunity was mediated predominantly by CD8+ and natural killer/lymphokine-activated killer (NK/LAK) cells. These data raise the possibility that a cell line altered previously for cytokine secretion may be readily modified to provide immunologic specificity for the neoplasms of individual cancer patients.

Molecular basis for the properties of the thyroxine-binding globulin-slow variant in American blacks.

Thyroxine-binding globulin-slow (TBG-S), a variant found in 4-12% of Black and Pacific Island populations, is inherited as an X-chromosome linked trait. This variant is detected on isoelectric focusing by the characteristic cathodal shift of all its isoforms, suggesting that the difference resides in the core protein. In addition, TBG-S is slightly more thermolabile, which explains why subjects expressing TBG-S have on the average lower serum TBG, and thus reduced T4, concentrations. We now report the molecular basis for this TBG variant, deduced from sequencing the TBG-S gene of an American Black man. Sequencing of the four coding regions and all intron/exon junctions revealed a single nucleotide substitution in the codon for amino acid 171 of the mature protein. The resulting change of the codon GAC to AAC results in replacement of the normal aspartic acid by asparagine. Since the negative charge provided by the aspartic acid is lost when replaced by the neutral asparagine, this substitution seems responsible for the cathodal shift on isoelectric focusing and slower electrophoretic mobility of TBG-S. An identical nucleotide substitution was identified in an unrelated American Black man expressing TBG-S. Whether the TBG-S phenotype observed in populations from the Pacific Islands is caused by the same mutation remains to be determined.