Differential posttranscriptional regulation of androgen receptor gene expression by androgen in prostate and breast cancer cells.

Androgens, via the androgen receptor (AR), modulate the growth and proliferation of prostate and breast cancer cells. However, the molecular mechanisms underlying the regulation of AR gene expression by androgen in these cells remain to be fully elucidated. To explore differences in AR gene expression between these hormone-responsive tumor cell types, we studied androgen-responsive LNCaP prostate cancer and AR positive MDA453 breast cancer cells. Dihydrotestosterone (DHT) 10 nM increased LNCaP cell proliferation and the proportion of LNCaP cells in S-phase of the cell cycle but inhibited MDA453 cell proliferation and reduced the proportion of MDA453 cells in S-phase of cell cycle. In both these cell lines, DHT decreased total AR messenger RNA (mRNA) but increased AR protein. In LNCaP cells, DHT down-regulated AR mRNA transcription but stabilized AR mRNA. In contrast, in MDA453 cells, DHT had no effect on AR mRNA transcription but destabilized AR mRNA. In summary, transcriptional down-regulation induced by androgens in LNCaP cells results in down-regulation of steady-state AR mRNA despite an androgen-induced increase in AR mRNA stability. However, in MDA453 cells, posttranscriptional destabilization of AR mRNA appears to be the predominant mechanism resulting in down-regulation of AR mRNA by androgen. These results demonstrate cell-specific and divergent regulation of AR mRNA turnover by androgen and identify a novel pathway of androgen-induced posttranscriptional destabilization and down-regulation of AR mRNA in human breast cancer cells. Furthermore, these data establish an important role for posttranscriptional pathways in the regulation of AR gene expression by androgen in human prostate and breast cancer cells.

BALB/c myeloma retroviruses have mink cell focus-inducing activity.

We have determined the in vitro host range of the cloned MO-21 and FL-1 murine myeloma retroviruses grown in SC-1 cells that were originally isolated from cloned MOPC-21 and FLOPC-1 BALB/c plasmacytoma cell lines. These viruses are able to replicate in murine (BALB/3T3, NIH/3T3) as well as numerous heterologous cell lines. These myeloma retroviruses also exhibit mink cell focus-inducing activity. MO-21 and FL-1 shared interference patterns with each other, but their replication was not interfered with by ecotropic, xenotropic, or amphotropic viruses. The lack of cross-interference with ecotropic or xenotropic viruses distinguishes these isolates from other mink cell focus-inducing viruses.

BALB/c myeloma retroviruses: peptide mapping and immunological analysis of the pp12 structural protein.

We have compared the pp12 structural protein of the MO-21 and FL-1 BALB/c myeloma retroviruses with the pp12 of several prototype retroviruses. Chymotryptic peptide maps of 125I-labeled, immune-precipitated pp12 proteins revealed that the MO-21 and FL-1 proteins can be distinguished from one another. The MO-21 pp12 most closely resembled the NIH-xenotrophic virus pp12, and the FL-1 pp12 most closely resembled the pp12 of BV-2 and WN 1802 B. Competition radioimmunoassay studies showed that the MO-21 and FL-1 pp12 proteins are also antigenically distinct from one another and that both contain pp12 antigenic determinants of a xenotropic virus. These data support our proposal that these two BALB/c viruses contain a gag gene that was generated by recombination between endogenous eco- and xenotropic viral sequences.

Effect of plant lectins on murine myeloma cells.

The mitogenic response (determined by uptake of [3H]-thymidine) of two different BALB/c myeloma lines, normal BALB/c spleen cells and spleen cells from tumour-bearing mice in primary culture to PHA, Con A, PWM and Robinia pseudoaccacia (RPA) extract was determined by measuring the uptake of [3H]-thymidine over 96 h. The pattern of the response of tumour and tumour-spleen cells to the 4 different lectins was similar, and different from that of normal spleen cells. The unstimulated cultures of tumour and tumour-spleen cells displayed an initial increased uptake of [3H]-thymidine, whereas stimulated cultures displayed a low initial uptake of label. After an initial phase of inhibition, ADJ-PC5 myeloma cells were stimulated by PHA and PWM to a greater extent than were normal spleen cells. On the other hand, normal spleen cells gave a markedly better response to Con A and RPA. The mitogenic response of tumour-spleen cells to all 4 lectins was intermediate between those observed for tumour and normal spleen cells; they responded better to Con A and RPA than did tumour cells but were not as responsive as spleen cells, whereas the converse was true for their response to PWM and PHA. In agreement with other reports, the data suggest that the responsiveness of tumour-spleen cells was due to the presence of tumour cells in this tissue. These results indicate that there is no definite evidence of an impaired lectin-responsiveness in lymphoid cells of mice bearing a myeloma.

Perineural angiogenesis in mice bearing subcutaneous tumours.

Cells of myeloma or fibrosarcoma were inoculated s.c. into BALB/c mice. Intact skins and tissue sections from animals killed at periodic intervals after inoculation of tumor cells were examined macroscopically and microscopically. The development of new blood vessels, probably involved in vascularization of the tumor, was observed around the nerves adjacent to the deposit of tumour cells. This occurred 5 days after inoculation of cells and before the tumour had a mean diameter of less than 1 mm. Lesser degrees of "perineural angiogenesis" were noted after s.c. inoculation of mineral oil, Freund's complete adjuvant or implantation of intact spleen, but none was observed with killed tumour cells.

Circulating lymphocytes and the spread of myeloma. Review of the evidence.

Patients with myeloma harbour circulating lymphocytes which bear the idiotypic determinants (SIg-id+ cells) of their own myeloma protein. Circulating white cells with abnormal karyotypes have been found in other patients with this disease. SIg-id+ lymphocytes have also been identified in the peripheral blood of myeloma-tumour-bearing mice. Murine myelomas have been propagated in vivo from circulating mononuclear cells that possessed myeloma-tumour-associated antigens. This and other evidence reviewed here points strongly to the involvement of circulating lymphocyte-like stem cells in the spread of human myeloma.

Circulating tumor cells in murine myeloma.

BALB/c mice bearing subcutaneous ADJ-PC5 myelomas had hematologic findings suggestive of a preleukemic syndrome: thrombocytopenia, anemia, leukocytosis, and megakaryocytic hyperplasia. Six BALB/c myelomas were successfully transplanted sc by fragments or cell suspensions of spleens from mice bearing a subcutaneous tumor, though typical myeloma cells were difficult to visualize by light microscopy in these spleens. The fidelity of transmission of the ADJ-PC5 myeloma by this procedure was shown by the retention of idiotypic specificity of the immunoglobulin produced by the tumor in a radioimmunoassay. The tumorigenic cell that homed to the spleen was apparent as early as 8 days after sc transplantation of the myeloma. The spleens of tumor-bearing mice, however, could destroy or suppress the expansion or growth of a limited number of cells that had migrated to the spleens. Tumorigenic cells present in the peripheral circulation constituted 2-3% of the leukocytes. These cells, however, had reduced levels of the murine myeloma viral and cell-associated antigens, were difficult to detect by an indirect immunofluorescence assay, and did not rapidly divide in this environment, as indicated by the very low number of cells detected by autoradiography.

Development of monoclonal IgA and an apparent IgG in a patient with macroglobulinemia: sharing of individually specific antigenic determinants among IgM, IgA, and IgG.

Patient CM, who initially was diagnosed as having macroglobulinemia (IgM, kappa) was subsequently found to develop a monoclonal IgA(kappa) protein. Rabbit antisera directed against the patient's IgAm and IgM were rendered specific for individual antigenic (ind) determinants. The anti-IgAm and IgM ind sera reacted with both 131I labeled monoclonal proteins in a double antibody radioimmunoassay (RIA). In addition, both monoclonal immunoglobulins inhibited the reaction between labeled immunoglobulin and both ind antisera, and statistical analysis of the data suggested that the shared ind determinants were identical. The IgG fraction of patient CM's serum also contained a component which competed with both monoclonal IgA (CM) and IgM (CM) in the RIA specific for ind determinants. Analysis of serum samples taken over a 2-year period revealed that, in addition to IgM, both the IgA and IgG components possessing the shared ind determinant(s) were present in low concentrations in the earliest sample, although not detected by conventional techniques. The monoclonal IgA and the IgG component were found to increase in concentration over this time interval with a concomitant decrease in IgM. The regulation of immunoglobulin expression with respect to the proposed models of gene organization in antibody-producing cells was discussed.

Intracisternal A particles from FLOPC-1 BALB/c myeloma: presence of high-molecular-weight RNA and RNA-dependent DNA polymerase.

Intracisternal A particles from the FLOPC-1 line of BALB/c myeloma have been shown to contain high-molecular-weight RNA (60 to 70S) that is sensitive to RNase, alkali degradation, and heat but resistant to Pronase treatment. The intracisternal A-particle RNA contains tract of poly (A) approximately 180 nucleotides long. As shown in a reconstitution experiment, by antigenic analysis of A-particle preparation and the SC cytopathogenicity assay, the 70S RNA was not due to contamination by type C virus particles. The FLOPC-1 intracisternal A particles also possess an endogenous RNA-dependent DNA polymerase. The enzyme required Mn2+ or Mg2+, dithiothreitol, detergent, and four deoxyribonucleoside triphosphates for maximum activity. Enzymatic activity was maximally stimuated by poly (rC)-oligo (dG)12-18 and less with poly (rG)-oligo (dC)10 or poly (rA)-oligo (dT)12-18 as compare with synthetic DNA/DNA duplex templates such as poly (dA)-oligo (dT)12-18. The enzyme can utilize the A-particle endogenous RNA as template as shown by analysis of the early and late DNA products of the endogenous reaction by CsSO4 isopycnic gradient centrifuation and hybridization of purified 70S or 35S A-particle RNA with the purified complementary DNA product. Approximately 50% of the A-particle complementary DNA also hybridized with oncornavirus RNA.