Evidence of an EGF/TGE-alpha--independent pathway for estrogen-regulated cell proliferation

To elucidate the relationship between epidermal growth factor (EGF)/transforming growth factor (TGF-alpha) and estradiol-17 beta (E) in cell proliferation, we examined their effects on the breast cancer cell line, CAMA-1. While E was able to consistently induce cell proliferation under a variety of experimental conditions, EGF/TGF-alpha was without effect. Despite the presence of the receptor (EGFR) gene, mature EGFR protein and mRNA were not detected by radioreceptor assay, 35S Met-labelling, and the Intron Differential RNA/PCR method under conditions in which cells remain responsive to E. Furthermore, TGF-alpha is not an autocrine factor in CAMA-1 cells. We demonstrated unequivocally that EGF/TGF-alpha interaction with EGFR is not an obligatory event in mediating estrogen-stimulated cell proliferation.

Polymerase chain reaction (PCR) amplification for the detection of porcine parvovirus

A polymerase chain reaction (PCR) amplification method was developed and evaluated to detect porcine parvovirus (PPV). A pair of 20-base primers and an oligonucleotide probe were derived from the DNA sequences common to two isolates of PPV, NADL-8 and NADL-2. The primers flanked 118-bp nucleotides within the region coding for the major structural protein VP2. After DNA amplification of PPV replicative form (RF), a 158-bp fragment was detected in agarose gels. This amplified fragment was shown to be specific for PPV DNA after Southern transfer and hybridization to a 20-base internal probe. The amplified fragment also contained a single EcoRI cleavage site. Various conditions, such as number of cycles and annealing temperature, were examined to optimize the conditions for detecting viral DNAs from infected cell cultures and swine fetal tissues. Four different isolates of PPV, NADL-8, NADL-2, KBSH and Kresse, and two other viruses, canine parvovirus (CPV) and pseudorabies virus (PRV), were included to determine specificity of amplification. Slot blot hybridization with a radiolabeled probe was used to evaluate the sensitivity of PCR amplification. The optimized protocol was specific for PPV detecting equally all four strains of PPV, but failing to amplify CPV or PRV sequences. The PCR method could detect at least 100 fg of viral replicative form (RF) DNA or the equivalent of 1 PFU of infectious virus. The applications of this method include routine detection of PPV in clinical samples and as a contaminant in mammalian cell lines.

Survey of oncogene and growth factor/receptor gene expression in cancer cells by intron-differential RNA/PCR

To elucidate the possible roles of proto-oncogenes and growth factors in estrogen-regulated cell proliferation of human breast and gynecologic cancers, we have determined the gene expressions of c-myc, transforming growth factor-alpha and beta 1 (TGF-alpha, beta 1) and epidermal growth factor receptor (EGFR) in a number of these cancer cell lines by using an intron-Differential (ID) RNA/PCR method, which differentially identifies the amplified cDNA from PCR products of genomic DNA contaminants. With this method, we demonstrated the expression of these genes, except EGFR, in an estrogen-dependent breast cancer cell line (CAMA-1). Our results show that TGF-alpha/EGF does not function as an autocrine factor in this cell line. Accordingly, it is unlikely that the TGF-alpha/EGFR system participates as a mediator in the estrogen-induced cell proliferation of CAMA-1 cells. The ID RNA/PCR method is a rapid, sensitive and specific technique for mRNA phenotyping and will have great clinical utility.