Reliable markers to distinguish human colon carcinoma from normal colonic epithelium are needed particularly for poorly differentiated tumors where no useful marker is currently available. To search for markers we constructed cDNA libraries from human colon carcinoma cell lines and screened for clones that hybridize to a greater degree with mRNAs of colon carcinomas than with their normal counterparts. Here we report one such cDNA clone that hybridizes with a 1.2-kilobase (kb) mRNA, the level of which is approximately equal to 9-fold greater in colon carcinoma than in adjacent normal colonic epithelium. Blot hybridization of total RNA from a variety of human colon carcinoma cell lines shows that the level of this 1.2-kb mRNA in poorly differentiated colon carcinomas is as high as or higher than that in well-differentiated carcinomas. Molecular cloning and complete sequencing of cDNA corresponding to the full-length open reading frame of this 1.2-kb mRNA unexpectedly show it to contain all the partial cDNA sequence encoding 135 amino acid residues previously reported for a human laminin receptor. The deduced amino acid sequence suggests that this putative laminin-binding protein from human colon carcinomas consists of 295 amino acid residues with interesting features. Containing only two cysteine residues, the protein does not have consensus sequences for asparagine-linked glycosylation, amphipathic alpha-helix, or the N-terminal leader signal sequences for entry into endoplasmic reticulum, although hydrophobic segments for potential membrane associations exist. There is an unusual C-terminal 70-amino acid segment, which is trypsin-resistant (no lysine or arginine) and highly negatively charged (13 aspartic plus glutamic residues). Within this segment are five repeats of (Asp/Glu)-Trp-(Ser/Thr); two of these are nearly tandem repeats of Thr-Glu-Asp-Trp-Ser-Ala-Xaa-Pro.

The SPOC1 cell, a novel goblet cell line derived from rat trachea, was tested for its ability to exhibit regulated mucin secretion in response to purinergic (P2) agonists. High-molecular mass glycoconjugates (HMMGs) purified by CsCl-density-gradient centrifugation had a buoyant density of 1.45 g/ml. The purified HMMG material exhibited a single major band with an apparent molecular mass of greater than 1000 kDa in SDS/ polyacrylamide gels stained with silver or blotted and stained with soya-bean agglutinin. [3H]HMMG was resistant to proteoglycan-degrading enzymes, but was susceptible to neuraminidase. The HMMG was approx. 91% carbohydrate by weight, and the glycosides were O-linked. The HMMG amino acid composition was enriched in Ser and Thr (sum 27%). Thus SPOC1-cell HMMG possess the characteristics of mucin. Mucin secretion by SPOC1 cells, grown on permeable supports and perfused luminally, was stimulated by ATP, UTP and adenosine 5'-[gamma-thio]triphosphate (100 microM) 4-5-fold over a baseline of 4 ng/min. The three dose-effect relations were nearly identical (K0.5 approximately 4 microM). SPOC1 cells grown on plastic and rat tracheal epithelial primary cells responded similarly to ATP and/or UTP. SPOC1 cells failed to respond to other purinergic agonists, either luminally or serosally, and consequently seem to possess an apical membrane P2u purinoceptor. SPOC1-cell total RNA was probed for P2u purinoceptor mRNA. Using conserved primers for both reverse transcriptase and PCR, a single band of the predicted size was observed, which had a nucleotide base sequence identical with the rat P2u purinoceptor mRNA. Thus SPOC1 cells secrete mucin under the control of a P2u purinoceptor; they should prove useful in dissecting the associated cellular regulatory pathways.

Summary To evaluate the risk of second primary myeloid leukaemia due to radiotherapy and chemotherapy administered for a first primary cancer, we conducted a population-based case-control study consisting of 97 cases and 194 controls matched on age, date of diagnosis, and site of initial primary cancer among residents of 13 counties in western Washington State. The risk of myeloid leukaemia in patients who received cyclophosphamide as part of their chemotherapy regimen was 7.4 (95% confidence interval 1. 3-43.8). This risk was not altered appreciably by the administration of radiotherapy. Compared to patients not receiving any chemotherapy, the relative risk among patients who received prednisone in combination with cyclophosphamide (odds ratio 44.4 95% confidence interval 4.0-496.2) was nearly four times that among patients receiving cyclophosphamide without this steroid (odds ratio 12.6 95% confidence interval 2.4-64.9). The relative risk of second primary myeloid leukaemia in patients who received both prednisone and drugs other than cyclophosphamide (odds ratio 64.2 95% confidence interval 2.6-1582) was 20 times that among patients receiving drugs other than cyclophosphamide and no prednisone (odds ratio 3.2 95% confidence interval 0.6-16.9). These risk estimates were higher when the analysis was restricted to acute myeloid leukaemia. There was no increased risk of second primary myeloid leukaemia associated with radiotherapy. The single unique finding is that the use of prednisone in chemotherapy regimens may enhance the leukaemogenic effect of other chemotherapy drugs.Development of a second cancer in general (Boivin & Hutchison, 1981;Valagussa et al., 1986; Pen, 1982;Rosner et al., 1982;Kushner et al., 1988;Tucker et al., 1988), and leukaemias in particular (Haas et al., 1987;Curtis et al., 1984;Einhorn, 1978;Boivin et al., 1986;Portugal et al., 1979;Rosner et al., 1978; Tucker et al., 1987;Reimer et al., 1977), following treatment for a first primary cancer is being increasingly reported. There is some evidence that the risk associated with treatment is greater for acute nonlymphatic leukaemia than other types of leukaemias (Van der Velden et al., 1988;Mehnert et al., 1986;Greene et al., 1983;Greene et al., 1982;Kaldor et al., 1990a; Kaldor et al., 1990b). Increased risks have been reported among patients receiving radiotherapy for cancer of the cervix, chemotherapy for cancers of the breast, ovary, non-Hodgkin's lymphoma and childhood cancer, as well as those receiving radiotherapy and chemotherapy for Hodgkin's disease (Boivin & Hutchison, 1981;Valagussa et al., 1986;Kushner et al., 1988;Tucker et al., 1988;Rosner et al., 1978; Tucker et al., 1987;Reimer et al., 1977;Van der Velden et al., 1988;Mehnert et al., 1986;Greene et al., 1983;Greene et al., 1982;Kaldor et al., 1990a; Kaldor et al., 1990b;Boice et al., 1987 (93%) controls. In the remainder, details were obtained from CSS abstract forms, which provide basic information on diagnosis, initial treatment and follow-up. However, none of these latter...

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