Stephen W. Carper

Methyl jasmonate decreases membrane fluidity and induces apoptosis through tumor necrosis factor receptor 1 in breast cancer cells.

In recent years, studies with plant compounds have shown both chemotherapeutic and chemopreventive properties. This study with plant stress hormones (jasmonates) showed growth inhibitory effects in breast cancer cells. cis-Jasmone and methyl jasmonate (MJ) inhibited the long-term proliferation of MDA-MB-435 and MCF-7 cells. Cell cycle analysis showed G0/G1 and S-phase arrest with increasing apoptotic population. Cellular signaling studies with MJ showed decreased membrane fluidity and activation of extrinsic and intrinsic apoptotic pathways. Specifically in extrinsic apoptotic pathway increased expression of TNF receptor 1, activation of mitogen-activated protein kinase and caspase-8 was observed. MJ also decreased the mitochondrial membrane potential and activated caspase-3 in breast cancer cells. In conclusion our results revealed novel-signaling mechanism of MJ in breast cancer cells, indicating that MJ could have potential applications for chemotherapeutic purposes.

Heat shock protein 27 stimulates recovery of RNA and protein synthesis following a heat shock

Constitutive expression of human hsp27 resulted in a 100‐fold increase in survival to a single lethal heat shock in CHO cells without effecting the development of thermotolerance. A possible mechanism for the thermoprotective function of hsp27 may be increased recovery of protein synthesis and RNA synthesis following a heat shock. A lethal heat shock (44°C, 30 min) results in a 90% reduction in the rate of protein synthesis in non‐tolerant cells. Control transfected cells recovered protein synthesis to a pre‐heat shock rate 10 h after the heat shock; while cell lines that constitutively express human hsp27 recovered 6 h after the heat shock. Thermotolerant cells had a 50% reduction in protein synthesis, which recovered within 7 h following the heat shock. The same lethal heat shock (44°C, 30 min) reduced RNA synthesis by 60% in the transfected cell lines, with the controls recovering in 7 h; while the hsp27 expressing cell lines recovered within 5 h. Thermotolerant cells had a 40% reduction in RNA synthesis and were able to recover within 4 h. The enhanced ability of hsp27 to facilitate recovery of protein synthesis and RNA synthesis following a heat shock may provide the cell with a survival advantage. J. Cell. Biochem. 66:153–164, 1997.

Perillyl alcohol and methyl jasmonate sensitize cancer cells to cisplatin.

Breast cancer is the second leading cause of cancer deaths among women in the United States. Several treatment options exist, with different side effects. To alleviate the side effects, several research groups have studied chemotherapeutic effects of plant compounds on cancer cells. These could be used as an alternative treatment option either alone or in combination with other chemotherapeutic drugs. The aim of this study was to evaluate the activity of a combination of perillyl alcohol (POH), methyl jasmonate (MJ) with cisplatin to define the most effective schedule and to investigate the mechanism of action in breast cancer cells. POH and MJ treatment (20% decrease in cell viability concentration) enhanced the cytotoxicity for subsequent exposure to cisplatin in MDA-MB-435 and MDA-MB-231 cells. Combination treatment of POH and MJ blocked cells at the G0/G1 phase of the cell cycle and the addition of cisplatin forced the cells to progress through the cell cycle and induced apoptosis. Apoptotic mechanistic studies indicated that POH and MJ treatment activated tumor necrosis factor receptor 1 and this was further increased by the addition of cisplatin. It was also found that mitochondrial membrane potential decreased with POH and MJ treatment; this effect was further enhanced by cisplatin treatment. These findings contributed to a better understanding of molecular mechanism of apoptosis in combination treatment of POH, MJ, and cisplatin. Results also showed that the combination treatment of three drugs is more effective than single drug alone or two drugs together.

Phenylboronic acid selectively inhibits human prostate and breast cancer cell migration and decreases viability

We compared the in vitro effect of boric acid (BA) versus phenylboronic acid (PBA) on the migration of prostate and breast cancer cell lines and non-tumorigenic cells from the same tissues. Treatment at 24 hours with BA (≤ 500 µM) did not inhibit chemotaxis on fibronectin in any cell line. However, treatment over the same time course with concentrations of PBA as low as 1 µM significantly inhibited cancer cell migration without effecting non-tumorigenic cell lines. The compounds did not affect cell adhesion or viability at 24 hours but did alter morphology; both decreased cancer cell viability at 8 days. These results suggest that PBA is more potent than BA in targeting the metastatic and proliferative properties of cancer cells.

Jasmonates induce apoptosis and cell cycle arrest in non-small cell lung cancer lines.

The jasmonates, cis-jasmone (CJ) and methyl jasmonate (MJ), were investigated for their effects against NSCLC cell lines A549 and H520. CJ or MJ inhibited the proliferation of both cell lines in a dose-dependent manner as well as induced cell cycle arrest in the G2/M phase. Apoptosis was observed following treatment with CJ or MJ as indicated by Hoechst staining and confirmed by dual annexin V-fluorescein isothiocyanate (FITC)/prodium iodide (PI) and DAPI (4′,6-diamidine-2′-phenylindole dihydrochloride) staining. p38 and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation was observed with increased expression of bax, p21, and caspase-3 activity. These observations indicate that jasmonates may have a therapeutic value in the treatment of lung cancer.

The Promise of Integrins as Effective Targets for Anticancer Agents.

This review will briefly describe integrin function, address why integrins are attractive targets for chemotherapeutic drug design, and discuss some ongoing studies aimed at inhibiting integrin activity. Integrins are cell surface heterodimeric receptors. They modulate many cellular processes including: growth, death (apoptosis), adhesion, migration, and invasion by activating several signaling pathways. Many potential chemotherapeutic agents target integrins directly (eg, polypeptides, monoclonal antibodies, adenovirus vectors). These agents may be clinically useful in controlling the metastatic spread of cancer.

Delayed Cytotoxic Effects of Methyl Jasmonate and cis-Jasmone Induced Apoptosis in Prostate Cancer Cells

Advanced prostate cancer cells are typically hormone independent, resistant to apoptosis and do not respond to chemotherapeutic agents. The ability of methyl jasmonate (MJ) and cis-jasmone (CJ) to inhibit growth in hormone independent prostate cancer cell lines, PC-3 and DU-145, was evaluated. CJ and MJ inhibited cell growth, induced cell cycle arrest and apoptosis. Detailed studies with the PC-3 cell line revealed that 2 mM CJ or MJ treatment resulted in caspase 3 activation and Tumor Necrosis Factor Receptor 1 (TNFR1) activation, all hallmarks of apoptosis. These phytochemicals could be useful in the management of advanced prostate cancer.

Regulation of HSP70 and HSP28 gene expression: absence of compensatory interactions.

We have previously reported the lack of HSP28 gene expression during acute and chronic thermotolerance development in L929 cells (J Cell Physiol 152: 118–125, 1992; Cancer Res 52: 5787, 1992). In contrast to HSP28, an extremely high level of inducible HSP70 synthesis was observed. These results led us to investigate the possibility of compensatory interactions between HSP70 and HSP28. To test the hypothesis, L929 cells were transfected with the human HSP28 gene contained in plasmid pCMV27. Data from Western blot and two-dimensional gel electrophoresis of [3H] leucine and [32P] orthophosphate-labeled proteins showed the synthesis and phosphorylation of HSP28 in transfected cells after heating at 45°C for 10 min. However, the expression of constitutive and inducible HSP70 genes, along with the synthesis of their proteins, was not decreased after heat shock. These results suggest an independent regulation of HSP28 and HSP70 gene expression.

Toremifene, a novel antiestrogen, can overcome hsp27-induced drug resistance in human breast cancer cells

Human breast cancer cell lines derived from MDA-MB-231 were constructed to express hsp27 constitutively. The elevated presence of this protein resulted in an enhanced ability to survive a heat shock and exposure to doxorubicin, a chemotherapeutic agent. Hsp27 expression was unable to protect cells from doxorubicin if they were cultured in the presence of toremifene. Flow cytometry analysis indicated that wells exposed to both toremifene and doxorubicin accumulate at G2 + M. Protective effects of hsp27 were overcome by addition of an estrogen antagonist at clinically nontoxic levels. Addition of toremifene to chemotherapeutic regimes may enhance the sensitivity of breast cancer cells to doxorubicin.

Comparison of ALA and Photofrin in two rat glioma models

Photodynamic therapy (PDT) shows good promise as an adjuvant therapy for the treatment of gliomas. PDT requires the use of a photosensitizer but there have been few studies in which they have been directly compared. Two rat brain glioma cell lines, BT4C and F98 were used to study the effects of Photofrin (PF) and aminolevulinic acid (ALA) as photosensitizers. Both compounds were able to sensitize cells to red light (635nm) however, PF treated (2.5 &mgr;g/ml) cells displayed more cell death than ALA treated (1 mM) cells. ALA-PDT treated cells did not have a block in the cell cycle while PF-PDT treated cells had a fluence dependent G1 block 24 hrs after treatment. The BT4C cell line also displayed a G2 cell cycle block. Both photosensitizers were able to induce apoptosis as measured by flow cytometry but only PF-PDT was able to induce necrosis at the fluence rates investigated (1-20 J/cm2). These differences in cellular responses to ALA and