Aspirin and aspirin-like drugs induce HLA-DR expression in HT29 colon cancer cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) decrease the incidence of colon cancer. The underexpression of HLA antigens during colon cancer development is suspected to be a mechanism by which malignant cells escape immune surveillance. We examined whether NSAIDs affect the expression of HLA-DR in HT29 human colon adenocarcinoma cells, which do not express HLA-DR. Aspirin, indomethacin and sulindac induced several-fold the expression of HLA-DR in these cells in a concentration- and time-dependent manner. Aspirin increased HLA-DR alpha steady-state mRNA levels and HLA-DR alpha gene transcription rate. These findings raise the possibility that such a mechanism may be operative in vivo.

Enhanced norepinephrine output during long-term desipramine treatment: a possible role for the extraneuronal monoamine transporter (SLC22A3)

To study the delay (2-6 weeks) between initial administration of norepinephrine reuptake inhibitor antidepressants and onset of clinical antidepressant action, we examined the effects of desipramine treatment on urinary and plasma catecholamines and their metabolites during the initial 6 weeks of treatment in depressed patients. Catecholamines and metabolites in 24-h urine collections and 8:00 a.m. plasma samples were measured at baseline and after 1, 4, and 6 weeks of desipramine treatment. Desipramine treatment produced significant increases in urinary norepinephrine (NE) and normetanephrine (NMN) and plasma NE at Weeks 4 and 6, but not at Week 1. The ratio of urinary NE/NMN was increased at Weeks 4 and 6, suggesting a reduction in the metabolism of NE to NMN at extraneuronal sites by Weeks 4 and 6. The increases in urinary NE and NMN and plasma NE at Weeks 4 and 6 of desipramine treatment were associated with a reduction in the conversion of NE to NMN. This would be compatible with a blockade of the extraneuronal monoamine transporter (organic cation transporter 3; SLC22A3) by NMN. Inhibition of the extraneuronal monoamine transporter may be an important component in the clinical pharmacology of the norepinephrine reuptake inhibitor antidepressant drugs, such as desipramine.

Signal transduction by platelet adenylate cyclase: alterations in depressed patients may reflect impairment in the coordinated integration of cellular signals (coincidence detection)

BACKGROUND

Adenylate cyclase (AC) responds to distinct but coincident signals from the agonist-stimulated G-protein Gs and the inhibitory G-protein Gi by generating a greater output signal-to-noise ratio--i.e., agonist-stimulated to basal ratio (fold-stimulation)--through coincidence detection than that generated by a single input (Gs) alone. Such coincidence detection by murine brain AC was found to be enhanced during chronic antidepressant treatment with imipramine.

METHODS

We examined and compared the basal, agonist-stimulated, and guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) or AlF4 ion postreceptor-stimulated AC activities in mononuclear leukocytes and platelets from the same blood specimens obtained from depressed patients (n = 27) and control subjects (n = 19).

RESULTS

In all subjects, the differences (delta GTP gamma S or delta AlF4) between postreceptor measures of AC in mononuclear leukocytes (where AC is regulated by Gs but not by Gi) and platelets (where AC is regulated by both Gs and Gi) were highly significant. In controls, the relationships between delta GTP gamma S or delta AlF4 and basal, agonist-stimulated, and the fold-stimulation of agonist-stimulated platelet AC resembled the regulation of AC by Gi in model-membrane systems. Comparable relationships between delta GTP gamma S or delta AlF4 and basal, agonist-stimulated, and the fold-stimulation of agonist-stimulated platelet AC activities were not observed in depressed patients.

CONCLUSIONS

Our results suggest that in controls, platelet AC enzyme activity is determined (in part) by the coordinated integration of signals from Gs and Gi through coincidence detection, while such coincidence detection by platelet AC may be impaired in patients with depressive disorders.

Staurosporine inhibits the proliferation, alters the cell cycle distribution and induces apoptosis in HT-29 human colon adenocarcinoma cells

Staurosporine (ST), a potent inhibitor of protein kinase C (PKC), was evaluated for its effect on the proliferation of HT-29 colon adenocarcinoma cells; PKC is associated with increased colon cell proliferation. ST inhibited cell proliferation in a time- and concentration-dependent manner by up to 90%. It also blocked the G2/M phase of the cell cycle and induced classical apoptosis (sub-diploid peak on flow cytometry, DNA ladder, and typical morphological changes). The kinetics of these changes suggest that low ST concentrations (2-20 nM) may act via a different mechanism from higher (100-1000 nM) ones. The role of ST, which is currently evaluated as an antitumor agent, in colon cancer requires further evaluation.