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Obesity has been linked with an increased risk of prostate cancer. The formation of toxic free oxygen radicals has been implicated in obesity mediated disease processes. Leptin is one of the major cytokines produced by adipocytes and controls body weight homeostasis through food intake and energy expenditure. The rationale of the study was to determine the impact of leptin on the metastatic potential of androgen-sensitive (LNCaP) cells as well as androgen-insensitive (PC-3 and DU-145) cells. At a concentration of 200 nm, LNCaP cells showed a significant increase (20% above control; P < .0001) in cellular proliferation without any effect on androgen-insensitive cells. Furthermore, exposure to leptin caused a significant (P < .01 to P < .0001) dose-dependent decrease in migration and invasion of PC3 and Du-145 prostate carcinoma cell lines. At the molecular level, exposure of androgen-independent prostate cancer cells to leptin stimulates the phosphorylation of MAPK at early time point as well as the transcription factor STAT3, suggesting the activation of the intracellular signaling cascade upon leptin binding to its cognate receptor. Taken together, these results suggest that leptin mediates the invasive potential of prostate carcinoma cells, and that this effect is dependent on their androgen sensitivity.

There are numerous similarities between the erythroid and megakaryocytic lineages which suggest that commitment to either lineage occurs relatively late in hematopoiesis. Commitment toward megakaryocyte development requires obligatory silencing of erythroidspecific genes. Therefore, we investigated the effects of interleukin-6, a known inducer of thrombocyte production, on globin gene expression during erythroid differentiation. Studies in K562 cells demonstrated inhibition of ␥ globin gene mRNA production and chain biosynthesis in the presence of exogenous interleukin-6 which was abrogated by anti-interleukin-6 monoclonal antibody. Similar studies in primary erythroid progenitors showed inhibition of burst-forming unit-erythroid colony formation when interleukin-6 was added late in cultures with decreased ␥ and ␤ globin gene mRNA production. Protein binding studies demonstrated an increase in activator protein-1 binding to its consensus sequence by 24 h of interleukin-6 treatment. Inhibition of activator protein-1 gene activity had no effect on ␥ gene silencing by interleukin-6. A potential interleukin-6 response element was identified in the ␥ globin gene. Interleukin-6 treatment led to a rapid increase in protein binding to the target DNA sequence. These results suggest that interleukin-6 may play an important role in globin gene silencing during megakaryocytic lineage commitment.

DNA-synthesis stage and total number of circulating burst-forming-units-erythroid (BFU-E) have been inversely correlated with hemoglobin F levels in the peripheral blood, as well as in the cells from the BFU-E-derived colonies obtained from homozygous sickle cell anemia (SS) patients during steady state. Similar studies in SS patients treated with cytotoxic agents have not been reported. However, regeneration of the erythroid marrow that follows the cytoreduction phase of chemotherapy has been suggested as one of the mechanisms of stimulation of fetal hemoglobin synthesis. Therefore, a longitudinal study of hemopoiesis in hydroxyurea-treated SS patients was conducted. Thirty-two sets of hemopoietic studies, including total circulating BFU-E and S-phase BFU-E, were obtained from three patients treated with hydroxyurea. A dose-dependent decrease in total BFU-E colonies occurred in peripheral blood of all three patients (r = -0.58, -0.85, and -0.97, respectively, with each P < 0.05). There was a strong positive correlation between hydroxyurea dose and fetal hemoglobin levels in two of the three patients who responded clinically (r = 0.89618 and 0.88632, respectively, with each P < 0.01). When data from all patients were combined (n = 32), there was a strong, inverse, linear relationship between total number of BFU-E and percentage S-phase BFU-E with fetal hemoglobin levels (r = -0.6649 and -0.7404, respectively, with each P < 0.0001). A stronger, curvilinear, multiple relationship was detected between total BFU-E and percentage S-phase BFU-E with fetal hemoglobin levels (R = 0.8351 and 0.8602 with each P < 0.0001).

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