Induction of growth inhibition and apoptosis in prostate cancer cells by flavopiridol

Flavopiridol is an inhibitor of several cyclin-dependent kinases, and exhibits potent growth-inhibitory activity against a number of human tumor cell lines both in vitro, and when grown as xenografts in mice. It has shown promising antineoplastic activity and is currently undergoing clinical phase II testing. Prostate cancer (PCa) remains a leading cause of morbidity and mortality among males in the United States. There are no effective treatments for hormone and/or radiation refractory PCa, suggesting that novel and newer treatment strategy may be useful in the management of PCa. Our previous study showed that flavopiridol induces cell growth inhibition and apoptosis in breast cancer cells. Here, we investigated whether flavopiridol was effective against prostate cancer cells. Flavopiridol was found to inhibit growth of PC3 prostate cancer cells. Induction of apoptosis was also observed in PC3 cells treated with flavopiridol, as measured by DNA laddering and PARP cleavage. We also found a significant down-regulation of Bcl-2 in flavopiridol-treated cells. These findings suggest that down-regulation of Bcl-2 may be one of the molecular mechanisms through which flavopiridol induces apoptosis and inhibits cell growth, suggesting that flavopiridol may be an effective chemotherapeutic agent against prostate cancer.     

Induction of apoptosis and inhibition of c-erbB-2 in MDA-MB-435 cells by genistein.

Breast cancer is the most common cancer and second leading cause of cancer related deaths in women in the United States. Genistein is a protein tyrosine kinase inhibitor and prominent isoflavonoid in soy products and has been proposed as the agent responsible for lowering the rate of breast cancer in Asian women. We have previously shown that genistein inhibits the growth of MDA-MB-231 breast cancer cells, regulates the expression of apoptosis-related genes, and induces apoptosis through a p53-independent pathway. In this study, we investigated these effects of genistein in the breast cancer cell line MDA-MB-435 and 435.eB cells that were established by transfecting c-erbB-2 cDNA into MDA-MB-435. We also investigated the effect of genistein on matrix metalloproteinase (MMP) secretion previously shown to be effected by erbB-2 transfection. Genistein was found to inhibit MDA-MB-435 and 435.eB cell growth. Induction of apoptosis was also observed in these cell lines when treated with genistein, as measured by DNA laddering, poly(ADP-ribose) polymerase (PARP) cleavage, and flow cytometric analysis. We also found an up-regulation of Bax and p21WAF1 expression and down-regulation of Bcl-2 and c-erbB-2 in genistein-treated cells. Gelatin zymography showed that genistein inhibits the secretion of MMP in the breast cancer cells. From these results, we conclude that genistein inhibits the growth of MDA-MB-435 breast cancer cells, induces apoptosis, regulates the expression of genes, and may inhibit invasion and metastasis of breast cancer cells. These findings suggest that genistein may be a potentially effective chemopreventive or therapeutic agent against breast cancer.     

Growth inhibition and apoptosis of myeloma cells by the CDK inhibitor flavopiridol.

Although myeloma shows responsiveness in intensive chemotherapy, overall survival remains less than 40% at 2 years. Since myeloma appears to be dependent on cytokines, such as IL-6, we hypothesized that targeting signal transduction molecules could effectively treat myeloma. Two myeloma cell lines U266 and RPMI-8226 and CD38+ myeloma cells were studied by immune complex kinase assay or anti-phosphotyrosine blot for evidence of constitutive activation of tyrosine kinases. Growth arrest and apoptosis were evaluated in these two cell lines following their treatment with specific kinase inhibitors. We found that a variety of Src and Janus kinases were present and constitutively active in U266 and RPMI-8226 cells. Inhibitors of both Src and Janus kinases were inferior to the cyclin-dependent kinase inhibitor, flavopiridol, in inducing both growth arrest with GI50 of 100 nM and apoptosis in both cell lines and CD38+ myeloma cells. Although, flavopiridol did not affect cyclin D1 and cyclin A levels, it inhibited Mcl-1 and Bcl-2 protein levels and cyclin-dependent kinase 2 activity. Flavopiridol is a well-tolerated drug, currently in phase I-II trials for a variety of tumors. A clinical trial using flavopiridol should be performed in patients with myeloma. Its mechanism of action may involve targets other than the cyclin-dependent kinases.     

Induction of apoptosis in breast cancer cells MDA-MB-231 by genistein.

Breast cancer is the most common cancer among American women, whereas Asian women, who consume a traditional diet high in soy products, have a relatively low incidence. Genistein is a prominent isoflavonoid in soy products and has been proposed as the agent responsible for lowering the rate of breast cancer in Asian women. We investigated the effects of genistein on cell growth and apoptosis-related gene expression in breast cancer cells MDA-MB-231. We found up-regulation of Bax and p21WAF1 expressions and down-regulation of Bcl-2 and p53 expression in genistein-treated cells. Furthermore, DNA ladder formation, CPP32 activation, and PARP cleavage were observed after treatment with genistein, indicating apoptotic cell deaths. Flow cytometry with 7-amino actinomycin D staining showed that the number of apoptotic cells increased with longer treatment of genistein. From these results, we conclude that genistein inhibits the growth of MDA-MB-231 breast cancer cells, regulates the expression of apoptosis-related genes, and induces apoptosis through a p53-independent pathway. The up-regulation of Bax and p21WAF1 may be the molecular mechanisms by which genistein induces apoptosis, however, further definitive studies are needed. These results suggest that genistein may be a potentially effective chemopreventive or therapeutic agent against breast cancer.     

Sequential dependent enhancement of caspase activation and apoptosis by flavopiridol on paclitaxel-treated human gastric and breast cancer cells.

Although in the past 10 years paclitaxel has emerged as a successful drug in cancer therapy, the overall response rate to this drug in patients with advanced metastatic disease remains low. Therefore, an understanding of the mechanism of the effect of paclitaxel on inducing apoptosis and the discovery of new ways to enhance the effect of paclitaxel will be critical to improving the therapeutic efficiency of this drug. In the present studies, we have determined that the cyclin-dependent kinase inhibitor flavopiridol significantly enhances paclitaxel-induced apoptosis in the human gastric and breast cancer cell lines MKN-74 and MCF-7. Flavopiridol enhances paclitaxel-induced apoptosis only when administered after paclitaxel treatment. The activation of caspases, specifically caspase 3, is enhanced by flavopiridol on paclitaxel-treated cells. In accordance with this, poly(ADP-ribose) polymerase cleavage is enhanced in combination therapy relative to single-agent paclitaxel. The induction of apoptosis, activation of caspase 3, and poly(ADP-ribose) polymerase cleavage in treatment regimens with paclitaxel and paclitaxel followed by flavopiridol were reversed by treatment with the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone, which supports the notion that caspases are the executioners of apoptosis in these processes. Paclitaxel alone causes transient mitotic arrest with activation of cdc-2 kinase. Cells exit mitosis in a specific time window without cytokinesis, with a decrease in cdc-2 kinase activity and MPM-2 labeling. Flavopiridol accelerates the mitotic exit when administered after paclitaxel treatment in association with a more rapid decrease in MPM-2 labeling. In contrast, pretreatment with flavopiridol prevents cells from entering mitosis by inhibiting cdc-2 kinase activity, thus antagonizing the paclitaxel effect. Therefore, in this study we show that potentiation of paclitaxel-induced apoptosis by flavopiridol is highly sequence dependent, such that mitotic entry and cdc-2 kinase activation by paclitaxel must precede flavopiridol therapy, and the synergistic effect of flavopiridol on paclitaxel-treated cells is due to enhancement in caspase activation.     

Inhibition of c-erbB-2 oncogene expression by estrogens in human breast cancer cells

The c-erbB-2 oncogene is thought to play a relevant role in the development and progression of mammary neoplasia. Using the human breast cancer cell lines T47D and MCF7, we found that the arrest of cell growth induced by a steroid-depleted medium was accompanied by a strong increase of c-erbB-2 mRNA and of the c-erbB-2-encoded p185 protein. The treatment of arrested cells with estrogens was found to resume cell proliferation and to inhibit dramatically c-erbB-2 expression at both mRNA and protein level. The regulation of c-erbB-2 expression was remarkably different from that observed for c-myc, which was strongly stimulated by estrogens, and ras, whose expression was unaffected all through the treatments. In addition, in the normal rat mammary gland undergoing development and differentiation during pregnancy and lactation, p185 expression was detected only in the functionally differentiated tissue. Altogether, our data indicate that the expression of c-erbB-2 is repressed during estrogen-induced proliferation and enhanced during growth arrest and/or differentiation of mammary cells.     

Specific inhibition of breast cancer cells by antisense poly-DNP-oligoribonucleotides and targeted apoptosis

Two membrane-permeable and RNase-resistant antisense poly-2'-O-(2,4-dinitrophenyl)-oligoribonucleotides (poly-DNP-RNAs) have been synthesized as inhibitors of human breast cancer, with nucleotide sequences complementary to the genes of RIalpha subunit of protein kinase A (RIalpha/PKA) and erbB-2, respectively. Both compounds inhibit the proliferation of SK-Br-3 breast cancer cells in culture above the concentration of 10 microg/ml, but have no effect on nontumorigenic MCF-10A breast cells. These antisense inhibitors also block the cell colony formation in methylcellulose medium, whereas the control poly-DNP-RNA with either random or sense sequence has no effect. RT-PCR data show that the antisense inhibition decreases the concentration of the mRNA. TdT-mediated dUTP nick-end labeling (TUNEL) fluorescence assay indicates that the targeted antisense inhibition by poly-DNP-RNAs leads to apoptosis of SK-Br-3 cells but does not affect nontumorigenic MCF-10A cells. The control poly-DNP-RNAs with random or sense nucleotide sequence are completely inactive.     

Sequence dependent potentiation of gemcitabine by flavopiridol in human breast cancer cells

Summary Purpose. Flavopiridol is a novel cyclin dependent kinase (cdk) inhibitor currently in Phase I and II clinical trials. We investigated the interaction between flavopiridol and gemcitabine in two human breast cancer cell lines.Experimental design. MCF-7 [Estrogen receptor (ER) positive] and MDA-MB-231 cells (ER negative) were treated with sub-cytotoxic concentrations of gemcitabine (G), flavopiridol (F), and flavopiridol followed by gemcitabine (F–G), or gemcitabine followed by flavopiridol (G–F) and assayed for biological activity. Results. Growth inhibition assessed by serial cell counting and MTT assay was highest in the G–F group. Significant increase in apoptosis assessed by flow cytometry, poly-ADP-ribose polymerase (PARP) and Caspase-3 degradation was also highest in the G–F group. Expression of pro-apoptotic Bax was up-regulated and anti-apoptotic Bcl-2 was down-regulated in only the G–F treated cells. Significant up regulation of p21^WAF-1 was demonstrated in the G–F group but not in the reverse regimen treated cells. No effect on protein kinase C (PKC) expression was seen in any of the treated cells. Conclusions. In conclusion, similar to the results in the gastrointestinal cell lines, a sequence dependent potentiation of the effect of gemcitabine by flavopiridol was demonstrated in breast cancer cell lines and it was independent of ER status. This was accompanied by enhanced apoptosis and the up regulation of p21^WAF-1 protein. These results provide rationale for pre-clinical evaluation of this treatment strategy using animal models and in the design of clinical trials of this drug in combination with cytotoxic therapy.     

Induction of cell cycle arrest and apoptosis in human breast cancer cells by quercetin

Quercetin, a widely distributed bioflavonoid, has been shown to induce growth inhibition in certain cancer cell types. In the present study we have pursued the mechanism of growth inhibition in MCF-7 human breast cancer cells. Quercetin treatment resulted in the accumulation of cells specifically at G2/M phase of the cell cycle. Mitotic index measured by MPM2 staining clearly showed that cells were transiently accumulated in M phase, 24 h after treatment. The transient M phase accumulation was accompanied by a transient increase in the levels of cyclin B1 and Cdc2 kinase activity. However, 24 h or longer treatment caused a marked accumulation of cells in G2 instead of M phase. Levels of cyclin B1 and cyclin B1-associated Cdc2 kinase activity were also decreased. We also found that quercetin markedly increased Cdk-inhibitor p21CIP1/WAF1 protein level after treatment for 48 h or longer, and the induction of p21CIP1/WAF1 increased its association with Cdc2-cyclin B1 complex, however, up-regulation of p53 by quercetin was not observed. Quercetin also induced significant apoptosis in MCF-7 cells in addition to cell cycle arrest, and the induction of apoptosis was markedly blocked by antisense p21CIP1/WAF1 expression. The present data, therefore, demonstrate that a flavonoid quercetin induces growth inhibition in the human breast carcinoma cell line MCF-7 through at least two different mechanisms; by inhibiting cell cycle progression through transient M phase accumulation and subsequent G2 arrest, and by inducing apoptosis.     

Induction of apoptosis by flavopiridol in human neuroblastoma cells is enhanced under hypoxia and associated with N-myc proto-oncogene down-regulation.

PURPOSE: Neuroblastoma is the most common extracranial solid tumor of children that arises from the sympathetic nervous system. Survival rates for neuroblastoma patients is low despite intensive therapeutic intervention, and the identification of new effective drugs remains a primary goal. The cyclin-dependent kinase inhibitor, flavopiridol, has demonstrated growth-inhibitory and cytotoxic activity against various tumor types. Our aim was to investigate flavopiridol effects on advanced-stage, N-myc proto-oncogene (MYCN)-amplified human neuroblastomas and the modulation of its activity by hypoxia, a critical determinant of tumor progression and a major challenge of therapy. EXPERIMENTAL DESIGN: Cell viability was monitored by 3-(4,5 dimethyl-2 thiazolyl)-2,5 diphenyl-2H tetrazolium bromide (MTT) and trypan blue dye exclusion assays; DNA synthesis was assessed with the bromodeoxyuridine pulse-labeling technique; apoptosis was studied by Giemsa staining, DNA fragmentation, terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling reaction, flow cytometric determination of hypodiploid DNA content, and evaluation of caspase activity and cytochrome c (CytC) release; MYCN expression was determined by Northern and Western blotting. RESULTS: Flavopiridol caused dose- and time-dependent decreases in neuroblastoma viability by inducing apoptosis, as confirmed by morphologic and biochemical criteria. Cell death was preceded by DNA synthesis inhibition and G1-G2 arrest, reversed by the pancaspase inhibitor, zVAD-fmk, and associated with caspase-3 and -2 activation and CytC increase. Moreover, flavopiridol strongly down-regulated MYCN mRNA and protein expression. Exposure to hypoxia enhanced both the extent of apoptosis and flavopiridol effects on CytC, caspase 3, and MYCN. CONCLUSIONS: These results indicate that flavopiridol has growth-inhibitory and apoptotic activity against advanced-stage neuroblastomas in vitro and is worthy of further investigation for the treatment of this disease.     

Induction of apoptosis in breast cancer cells by preoperative oral administration of 5-fluorouracil

We investigated whether 5-fluorouracil (5-FU) can induce apoptosis in breast cancer cells. Preoperatively, 23 breast cancer patients were divided into a group treated with 5-FU at 200 mg/day for 2 weeks (Group A) and a non-treatment group (Group B), and breast cancer tissues were taken postoperatively. DNA fragmentation by agarose electrophoresis and the TUNEL method were used to investigate the induction of apoptosis. The labeling rate with Ki-67 was measured to study the reproductive activity of tumor cells. The involvement of p53 in the apoptosis decision mechanism was also studied. DNA was more fragmented in Group A than in Group B. The apoptosis index by the TUNEL method was 1.88 +/- 1.03 in Group A, which was significantly higher than 0.36 +/- 0.86 in Group B. The labeling rate with Ki-67 was significantly higher in Group B(62.3 +/- 21.7) than in Group A (29.8 +/- 16.0). There was no difference in the protein expression of p53 regardless of the presence or absence of DNA fragmentation. These results indicate that 5-FU administration induces apoptosis in breast cancer cells and significantly inhibits their reproductive activity. Involvement of p53 in the apoptosis decision mechanism was not demonstrated.     

c-erbB-2 oncoprotein expression in primary and advanced breast cancer.

Immunoreactivity for c-erbB-2 oncogene product expression has been investigated in patients with breast cancer using the polyclonal antibody 21N. Three series of patients were studied, 602 presenting with primary operable cancer, 57 with stage 3 and 123 with stage 4 disease. Representative tissue sections of each primary tumour were stained using a standard immunoperoxidase technique. Invasive tumour membrane immunoreactivity was assessed and identified in 15% of patients with primary operable cancer and 20% in the advanced breast cancer group. The results demonstrate a relationship between poorer survival and oncogene expression in all three patient groups. Patients in the primary operable cancer group with membrane oncoprotein expression had a poorer outcome, 35% 10-year survival, compared with those in which membrane expression was absent, 55% 10-year survival. The median survival of patients with stage 3 disease with c-erbB-2 membrane positivity was 17 months compared to 24 months with membrane negativity. In stage 4 disease median survival with membrane expression was 8.8 months compared to 19.7 months with no membrane expression. In addition in the series of primary cancers a correlation existed between histological grade and membrane immunoreactivity. Multivariate analysis showed histological grade to be a more powerful prognostic factor than c-erbB-2 protein expression. In conclusion, this study demonstrates, in a large series of patients presenting to one centre, that c-erbB-2 protein expression is a prognostic indicator in patients with primary operable and advanced breast disease.     

Growth inhibition and induction of apoptosis in MCF-7 breast cancer cells by Antrodia camphorata

Antrodia camphorata (A. camphorata) is well known in Taiwan as a traditional Chinese medicine, and it has been shown to exhibit antioxidant and anticancer effects. In this study, therefore, its ability to induce apoptosis in cultured MCF-7 breast cancer cells was studied. Treatment of the MCF-7 cells with a variety of concentrations of the fermented culture broth of A. camphorata (25-150 microg/ml) resulted in dose- and time-dependent sequences of events marked by apoptosis, as shown by loss of cell viability, chromatin condensation, internucleosomal DNA fragmentation, and sub-G1 phase accumulation. Furthermore, apoptosis in the MCF-7 cells was accompanied by the release of cytochrome c, activation of caspase 3, and specific proteolytic cleavage of poly (ADP-ribose) polymerase (PARP). Although, the A. camphorata-induced apoptosis was associated with Bax protein levels, negligible Bcl-2 reduction was observed. Interestingly, A. camphorata induced dose-dependent reactive oxygen species (ROS) generation in MCF-7 cells. Analysis of the data suggests that A. camphorata exerts antiproliferative action and growth inhibition on MCF-7 cells through apoptosis induction, and that it may have anticancer properties valuable for application in drug products.     

神经酰胺诱导人乳腺癌细胞凋亡的研究

目的 :观察神经酰胺对人乳腺癌细胞株MCF 7及耐多柔比星细胞株MCF 7/ADR的诱导凋亡作用及其对bcl 2基因表达的影响 ,探讨神经酰胺诱导凋亡的机制。方法 :采用MTT法检测细胞生存率 ,用流式细胞术检测凋亡率 ,运用流式细胞术、RT PCR方法检测bcl 2基因表达。结果 :神经酰胺对MCF 7、MCF 7/ADR细胞有明显的抑制生长作用。 2 5 μmol/LC6 神经酰胺作用48h后 ,MCF 7及MCF 7/ADR细胞凋亡率分别为( 2 0 70± 2 66) %、( 12 3 9± 1 76) % ,前者凋亡率高于后者 ,P <0 0 1。流式细胞术检测 ,MCF 7、MCF 7/ADR细胞bcl 2蛋白阳性率分别为 ( 2 7 5 9± 2 94) %、( 79 5 6±3 2 0 ) %。MCF 7/ADR细胞经神经酰胺作用后 ,bcl 2蛋白及mRNA水平均降低。结论 :神经酰胺对MCF 7、MCF 7/ADR细胞有抑制生长及诱导凋亡作用 ,神经酰胺诱导凋亡可能是通过下调bcl 2基因表达而实现的     

Metastatic cancer cells from c-erbB-2 negative primary breast cancer maintain the original c-erbB-2/HIF1alpha phenotype

The expression of c-erbB-2 and HIF1alpha proteins is linked with an aggressive tumor phenotype and poor survival in breast cancer. In the present study we investigated whether this ominous effect is a result of c-erbB-2/HIF1alpha expressing clone appearance within the primary tumor, by examining the c-erbB-2/HIF1alpha expression status in the primary tumor, node metastasis and cancer cells invading into the lymphovascular spaces. The metastasizing cancer cell clones, whether migrating to the lymph nodes or entering into the systemic circulation maintained the original c-erbB-2/HIF1alphaphenotype of the primary tumor. Migrating c-erbB-2/HIF1alpha negative tumors do so through activation of alternative biologic pathways and not through positive clone appearance. These results strongly support the concept that targeted therapies against c-erbB-2 or against HIF1alpha can be guided with precision by the primary tumor c-erbB-2/HIF1alpha status without demanding the detection of the metastatic tumor phenotype.     

组蛋白酶和c-erbB-2在乳腺癌中的表达

目的探讨乳腺癌病人c-erbB．2和cath-D表达与临床病理及预后的关系。方法通过免疫组化法，检测128例乳腺癌病人的c-erbB-2和cath-D的表达。结果cath-D和c-erbB-2表达与肿块大小、淋巴结转移显著相关（P〈0．0001）。c-erbB-2表达比不表达病人预后差（P=0．01）。结论c-erbB-2阳性表达和cath-D阳性表达者，恶性程度高，易转移、预后差。     

Quantitation of c-erbB-2 gene amplification in breast cancer tissue by competitive PCR.

Controversy exists regarding the relationship of the degree of c-erbB-2 amplification to other prognostic factors in breast cancer. To determine the degree of amplification of c-erbB-2 exactly, a sensitive and quantitative method is required. We have developed a competitive PCR method to quantitatively determine the amplification of the c-erbB-2 oncogene. Using this method, we evaluated DNA from 27 breast cancer tissue specimens and DNA from peripheral blood leukocytes from a normal individual. Regarding the relationship between the degree of c-erbB-2 amplification and clinicopathological factors, we found a greater degree of amplification of the c-erbB-2 oncogene in estrogen receptor- negative or progesterone receptor-negative specimens than in positive ones and in lymph node metastasis-positive specimens than in negative specimens, in stages II, III, and IV of disease compared with stage I disease, and in samples with positive lymphatic vessel invasion than with no lymphatic vessel invasion. Generally, these factors were seen in the group of patients who had a bad prognosis. By univariate analysis and multivariate analysis, reverse correlation was observed between amplification of c-erbB-2 and overall survival. Regarding disease-free survival, these relationships were observed only with univariate analysis in our group of patients.