MEIS1, PREP1, and PBX4 are differentially expressed in acute lymphoblastic leukemia: association of MEIS1 expression with higher proliferation and chemotherapy resistance.

BACKGROUND: The Three-amino acid-loop-extension (TALE) superfamily of homeodomain-containing transcription factors have been implicated in normal hematopoiesis and in leukemogenesis and are important survival, differentiation, and apoptosis pathway modulators. In this work, we determined the expression levels of TALE genes in leukemic-derived cell lines, in blood samples of patients with Acute lymphoblastic leukemia (ALL), and in the blood samples of healthy donors. RESULTS: Here we show increased expression of MEIS1, MEIS2, and PREP1 genes in leukemia-derived cell lines compared with blood normal cells. High levels of MEIS1 and PREP1, and low levels of PBX4 expression were also founded in samples of patients with ALL. Importantly, silencing of MEIS1 decreases the proliferation of leukemia-derived cells but increases their survival after etoposide treatment. Etoposide-induced apoptosis induces down-regulation of MEIS1 expression or PREP1 up-regulation in chemotherapy-resistant cells. CONCLUSIONS: Our results indicate that up-regulation of MEIS1 is important for sustaining proliferation of leukemic cells and that down-regulation of MEIS1 or up-regulation of PREP1 and PBX genes could be implicated in the modulation of the cellular response to chemotherapeutic-induced apoptosis.

Sensitization of cervix cancer cells to Adriamycin by Pentoxifylline induces an increase in apoptosis and decrease senescence.

BACKGROUND: Chemotherapeutic drugs like Adriamycin (ADR) induces apoptosis or senescence in cancer cells but these cells often develop resistance and generate responses of short duration or complete failure. The methylxantine drug Pentoxifylline (PTX) used routinely in the clinics setting for circulatory diseases has been recently described to have antitumor properties. We evaluated whether pretreatment with PTX modifies apoptosis and senescence induced by ADR in cervix cancer cells. METHODS: HeLa (HPV 18+), SiHa (HPV 16+) cervix cancer cells and non-tumorigenic immortalized HaCaT cells (control) were treated with PTX, ADR or PTX + ADR. The cellular toxicity of PTX and survival fraction were determinated by WST-1 and clonogenic assay respectively. Apoptosis, caspase activation and ADR efflux rate were measured by flow cytometry, senescence by microscopy. IkappaBalpha and DNA fragmentation were determinated by ELISA. Proapoptotic, antiapoptotic and senescence genes, as well as HPV-E6/E7 mRNA expression, were detected by time real RT-PCR. p53 protein levels were assayed by Western blot. RESULTS: PTX is toxic (WST-1), affects survival (clonogenic assay) and induces apoptosis in cervix cancer cells. Additionally, the combination of this drug with ADR diminished the survival fraction and significantly increased apoptosis of HeLa and SiHa cervix cancer cells. Treatments were less effective in HaCaT cells. We found caspase participation in the induction of apoptosis by PTX, ADR or its combination. Surprisingly, in spite of the antitumor activity displayed by PTX, our results indicate that methylxantine, per se does not induce senescence; however it inhibits senescence induced by ADR and at the same time increases apoptosis. PTX elevates IkappaBalpha levels. Such sensitization is achieved through the up-regulation of proapoptotic factors such as caspase and bcl family gene expression. PTX and PTX + ADR also decrease E6 and E7 expression in SiHa cells, but not in HeLa cells. p53 was detected only in SiHa cells treated with ADR. CONCLUSION: PTX is a good inducer of apoptosis but does not induce senescence. Furthermore, PTX reduced the ADR-induced senescence and increased apoptosis in cervix cancer cells.

Gossypol induced apoptosis of polymorphonuclear leukocytes and monocytes: involvement of mitochondrial pathway and reactive oxygen species.

The aim of this study was to determine how gossypol affects the viability and activity of polymorphonuclear leukocytes and monocytes in blood obtained from healthy donors. Loss of mitochondrial membrane potential (delta psi m) and apoptosis was maximized in human polymorphonuclear leukocytes and monocytes after incubation with gossypol. Pretreatment with a caspase-9 inhibitor or antioxidants (superoxide dismutase or Trolox) inhibited gossypol-induced loss of the delta psi m and apoptosis. Likewise, we observed participation of caspase -3, -7, and -10 in gossypol-induced apoptosis. Expression of the proapoptotic genes bax, bak, bad and p53/Tp53 increased in polymorphonuclear leukocytes exposed to gossypol. The expression of the anti-apoptotic genes bcl-(XL) and mcl-1 was reduced when polymorphonuclear leukocytes and monocytes were treated with gossypol. Gossypol treatment also inhibited yeast phagocytosis by these cells. We concluded that gossypol induces apoptosis in phagocytic cells and that this effect was dose-dependent. The findings in this report may be important to consider in light of possible gossypol use in clinical strategies for cancer treatment.

Apoptosis induction in Jurkat cells and sCD95 levels in women's sera are related with the risk of developing cervical cancer.

BACKGROUND: Currently, there is clear evidence that apoptosis plays an important role in the development and progression of tumors. One of the best characterized apoptosis triggering systems is the CD95/Fas/APO-1 pathway; previous reports have demonstrated high levels of soluble CD95 (sCD95) in serum of patients with some types of cancer. Cervical cancer is the second most common cancer among women worldwide. As a first step in an attempt to design a minimally invasive test to predict the risk of developing cervical cancer in patients with precancerous lesions, we used a simple assay based on the capacity of human serum to induce apoptosis in Jurkat cells. We evaluated the relationship between sCD95 levels and the ability to induce apoptosis in Jurkat cells in cervical cancer patients and controls. METHODS: Jurkat cells were exposed to serum from 63 women (20 healthy volunteers, 21 with cervical intraepithelial neoplasia grade I [CIN 1] and 22 with cervical-uterine carcinoma). The apoptotic rate was measured by flow cytometry using Annexin-V-Fluos and Propidium Iodide as markers. Serum levels of sCD95 and soluble CD95 ligand (sCD95L) were measured by ELISA kits. RESULTS: We found that serum from almost all healthy women induced apoptosis in Jurkat cells, while only fifty percent of the sera from women with CIN 1 induced cell death in Jurkat cells. Interestingly, only one serum sample from a patient with cervical-uterine cancer was able to induce apoptosis, the rest of the sera protected Jurkat cells from this killing. We were able to demonstrate that elimination of Jurkat cells was mediated by the CD95/Fas/Apo-1 apoptotic pathway. Furthermore, the serum levels of sCD95 measured by ELISA were significantly higher in women with cervical cancer. CONCLUSION: Our results demonstrate that there is a strong correlation between low levels of sCD95 in serum of normal women and higher apoptosis induction in Jurkat cells. We suggest that an analysis of the apoptotic rate induced by serum in Jurkat cells and the levels of sCD95 in serum could be helpful during the prognosis and treatment of women detected with precancerous lesions or cervical cancer.

MG132 proteasome inhibitor modulates proinflammatory cytokines production and expression of their receptors in U937 cells: involvement of nuclear factor-kappaB and activator protein-1.

In response to inflammatory stimuli, monocytes/macrophages secrete greater quantities of the proinflammatory cytokines tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and IL-6. The inflammatory process and the innate immune response are related to the activation of several transcription factors, such as nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1). The proteasome is a multimeric protease complex, which plays a vital role in several cellular functions, including the regulation of transcription factors like NF-kappaB. In this study, we used the human monocyte cell line U937 stimulated with lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMA) as a model to investigate the in vitro effects of MG132, a proteasome inhibitor, on the release of TNF-alpha, IL-1beta and IL-6 and on the expression of their membrane and soluble receptors TNF-R1, IL-1R1 and IL-6R. We also analysed the effects of MG132 on the activation of NF-kappaB and AP-1 and on the IkappaB molecule. MG132 significantly inhibited the secretion of those proinflammatory cytokines. MG132 increased the release of the soluble receptors TNF-R1 and IL-1R1 from U937 cells and decreased their cell-surface expression. MG132 also increased IL-6R cell-surface expression and decreased its release. Proteasome inhibition also led to an increase in LPS+PMA-induced AP-1 activation and the attenuation of LPS+PMA-induced IkappaB degradation, resulting in the abolition of NF-kappaB activation. Our experiments strongly suggest that the proteasome is an important factor in the regulation of proinflammatory cytokines and their receptors.