Detection Of Annexin Research Articles

Homoharringtonine induces apoptosis and growth arrest in human myeloma cells

Homoharringtonine (HHT) is a plant alkaloid with antileukemic activity which is currently being used for treatment of acute and chronic leukemias. The present studies have evaluated the effect of HHT on proliferation and apoptosis in human myeloma cells. Myeloma cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyl tetrazolium bromide (MTT) assay. Apoptotic cells and cell cycle were evaluated by flow cytometry. Level of caspase-8, caspase-9, caspase-3, and DNA repair enzyme poly (ADP-ribose) polymerase (PARP), were investigated using Western blot analysis. We found that HHT significantly inhibited the proliferation of human multiple myeloma (MM) cell lines and tumor cells from patients with relapsed refractory MM in a dose-dependent manner. HHT also induced apoptosis in myeloma cells as evidenced by flow cytometric detection of annexin V binding assay. This apoptotic process was associated with the activation of caspase-8, caspase-9, caspase-3 and PARP. The results also demonstrate that HHT potentiates dexamethasone-induced killing of MM cells. These findings indicate that HHT may be effective in the treatment of MM.

Potent Cytotoxicity Against Multiple Myeloma and Acute Myeloid Leukemia Cells by a New Histone Deacetylase Inhibitor ITF2357.

ITF2357 (Italfarmaco, Italia) is a novel hydroxamic acid-based HDAC inhibitor (HDACi) that has shown reduced toxicity in phase I studies. We have investigated the cytotoxic and anti-proliferative activities of ITF2357 in multiple myeloma (MM) and acute myelogenous leukaemia cells (AML). ITF2357 had a strong cytotoxic activity in 8/9 MM and 6/6 AML cell lines, with a mean IC50 of about 0.2 μM, a concentration largely attained following oral administration of safe doses of ITF2357 to healthy individuals. In contrast SAHA, the prototypic hydroxamic HDACi, showed an IC50 of about 1 μM or above in all cases. The cytotoxic activity of ITF2357 was due to induction of apoptosis, as documented by detection of annexin V and cleaved caspase 3. The ITF2357 induced hyperacetylation of histones in cell lines resistant or sensitive to the cytoytoxic activity of the drug is under investigation in order to further define its mechanism of action. ITF2357 had also more potent cytotoxic activity compared to SAHA against freshly isolated CD138+ purified MM cells and AML samples, with an IC50 of about 0.1 μM in 3/3 MM and 13/15 AML cases. Sensitive AML cases included five cases of FAB M1, five M2 and three M4. Three of the sensitive cases carried a t(8;21) translocation, 2 an inv(16), 6 had a normal and 2 a complex karyotype. Furthermore four of the sensitive AML also carried a flt3 internal tandem duplication and 3 a type A mutation in the nucleophosmin 1 gene (NPM1). The 2 more resistant AML cases (one M1 and one M5, both with normal karyotype) showed nonetheless a response to the drug with an IC50 of about 0.5 μM. We have also developed a culture system to grow freshly isolated AML cells for at least 3 weeks in vitro on human mesenchymal cells (MSC). Interestingly, ITF2357 was cytotoxic for primary AML cells stimulated to grow in optimal conditions on MSCs, at the same dose as in standard short term cultures. In contrast ITF2357 was not cytotoxic for MSCs even at the 1 μM concentration. The strong cytotoxic activity of ITF2357 on MM and AML has provided the framework for ongoing phase I studies of ITF2357 in these malignancies.

Cimicifuga racemosa Extract Inhibits Proliferation of Estrogen Receptor-positive and Negative Human Breast Carcinoma Cell Lines by Induction of Apoptosis

Hormone replacement therapy is contraindicated in women with breast cancer. Extracts from the rhizomes of Cimicifuga racemosa, have gained acceptance as a natural alternative for the treatment of menopausal symptoms. In the present study we investigated the antiproliferative activity of C. racemosa extracts (isopropanolic and ethanolic) on the estrogen receptor positive MCF-7 and estrogen receptor negative MDA-MB231 breast cancer cells by WST-1 assay. Down regulation of the proliferative activity and cell killing by isopropanolic and ethanolic extracts occurred in a clear dose-dependent response with a 50% growth inhibitory concentration of 54.1 +/- 11.4 and 80.6 +/- 17.7 micro g/ml in MCF-7 cells and of 29.5 +/- 3.0 and 58.6 +/- 12.6 microg/ml in MDA-MB231 cells, respectively. Further, the mode of cell death was identified as apoptosis by microscopic inspection and confirmed by light scatter characteristics and by detection of Annexin V adherence to phosphatidylserine by flow cytometry. In addition, the involvement of activated caspases was supported by the cleavage of cytokeratin 18 detected with M30 antibody. Increases in the level of M30-antigen of about 4-fold and 2-fold over untreated controls were observed in C. racemosa -treated MCF-7 and MDA-MB231 cells. These results indicate that C. racemosa extract exerts no proliferative activity, but kills the estrogen receptor positive MCF-7 as well as estrogen receptor negative MDA-MB231 cells by activation of caspases and induction of apoptosis.

Detection of annexin IV in bovine retinal rods.

The fraction of proteins capable of binding to photoreceptor membranes in a Ca2+-dependent manner was isolated from bovine rod outer segments. One of these proteins with apparent molecular mass of 32 kD (p32) was purified to homogeneity and identified as annexin IV (endonexin) by MALDI-TOF mass-spectrometry. In immunoblot, annexin IV purified from bovine rod outer segments cross-reacted with antibodies against annexin IV from bovine liver. This is the first detection of annexin IV in vertebrate retina.

Translocation of annexin I to plasma membranes and phagosomes in human neutrophils upon stimulation with opsonized zymosan: possible role in phagosome function.

Annexin I in the cytosol of resting neutrophils was translocated to the plasma membranes upon addition of opsonized zymosan (OZ). Maximum translocation could be detected 1 min after stimulation with OZ, and decreased thereafter. Subcellular fractionation studies demonstrated that annexin I could not be detected in the granule fractions in either resting or activated cells, but was found in association with the phagosome fraction. The marked translocation of annexin I was unique to OZ, since formyl-Met-Leu-Phe induced only slight translocation of annexin I to the plasma membranes, and phorbol 12-myristate 13-acetate had no effect at all. The mechanism regulating the translocation of annexin I is not clear. Annexin I is not phosphorylated in resting or stimulated cells. The correlation between the elevation in the intracellular calcium ion concentration ([Ca2+]i) and the degree of translocation of annexin I to the plasma membranes induced by the different stimuli, together with the inhibition of these processes by the addition of EGTA, indicate that the translocation of annexin I can probably be attributed to the rise in [Ca2+]i. However, this cannot be the sole mechanism since ionomycin, which caused an increase in [CA2+]i similar to that induced by OZ, was less efficient than OZ in inducing translocation of annexin I. The induction of annexin I translocation to the plasma membrane by OZ, which was the only agent that induced phagosome formation, and the detection of annexin I in the phagosome fraction, suggest that annexin I participates in phagosome function.