Inhibition of Rac1 signaling by lovastatin protects against anthracycline-induced cardiac toxicity

Normal tissue damage limits the efficacy of anticancer therapy. For anthracyclines, the clinically most relevant adverse effect is cardiotoxicity. The mechanisms involved are poorly understood and putative cardioprotectants are controversially discussed. Here, we show that the lipid-lowering drug lovastatin protects rat H9c2 cardiomyoblasts from doxorubicin in vitro. Protection by lovastatin is related to inhibition of the Ras-homologous GTPase Rac1. It rests on a reduced formation of DNA double-strand breaks, resulting from the inhibition of topoisomerase II by doxorubicin. Doxorubicin transport and reactive oxygen species are not involved. Protection by lovastatin was confirmed in vivo. In mice, lovastatin mitigated acute doxorubicin-induced heart and liver damage as indicated by reduced mRNA levels of the pro-fibrotic cytokine connective tissue growth factor (CTGF) and pro-inflammatory cytokines, respectively. Lovastatin also protected from doxorubicin-provoked subacute cardiac damage as shown by lowered mRNA levels of CTGF and atrial natriuretic peptide. Increase in the serum concentration of troponin I and cardiac fibrosis following doxorubicin treatment were also reduced by lovastatin. Whereas protecting the heart from harmful doxorubicin effects, lovastatin augmented its anticancer efficacy in a mouse xenograft model with human sarcoma cells. These data show that statins lower the incidence of cardiac tissue injury after anthracycline treatment in a Rac1-dependent manner, without impairing the therapeutic efficacy.     

Scavenging activity of indole compounds against cisplatin-induced reactive oxygen species

The antioxidant effects of indole compounds such as melatonin (MLT), tryptophan, and serotonin, on cisplatin (cis-diaminedichloroplatinum, or CDDP)-induced reactive oxygen species (ROS) generation were examined by electron spin resonance (ESR). In addition, DNA fragmentation by CDDP-induced ROS and the effect of MLT on it were analyzed in primary cultures of rat renal tubular epithelial cells. MLT and serotonin had scavenging effects on CDDP-induced hydroxy radicals (*OH), and the scavenging activity of MLT was higher than that of serotonin. The exposure of primary-cultured renal tubular cells to CDDP caused severe cytotoxicity. Tryptophan, serotonin, and 6-OH-MLT did not reduce the CDDP-induced cytotoxicity, whereas MLT did. CDDP exposure induced DNA fragmentation in primary-cultured renal tubular cells, but the simultaneous administration of MLT inhibited the DNA fragmentation. These results indicate that MLT inhibits CDDP-induced cytotoxicity by directly scavenging *OH, and that MLT markedly reduces renal cytotoxicity and DNA fragmentation caused by CDDP-induced ROS in vitro.     

Vitamin C increases the apoptosis via up-regulation p53 during cisplatin treatment in human colon cancer cells

Vitamin C (VC) is an important antioxidant and enzyme co-factor that works by stimulating the immune system and protecting against infections. It is well known that melanoma cells are more susceptible to VC than any other tumor cells. However, the role of VC in the treatment of colon cancer has not been studied. Cisplatin (CDDP) is a DNA damaging agent and is widely used for treating cancer, while the role of p53 in CDDP-induced cell death has been stressed. Using cell growth assays, morphological methods, Western blotting, flow cytometry, and DNA fragmentation analysis, we measured the expression of p53 level involved in the effect of VC on CDDP-induced apoptosis of HCT116, a human colon cancer cell line. CDDP plus VC treatment resulted in significantly increased apoptosis along with upregulation of p53 compared to untreated cells and/or CDDP-treated cells. These results suggest that VC enhanced CDDP sensitivity and apoptosis via upregulation of p53.     

An overview on the biological activity and anti-cancer mechanism of lovastatin

Lovastatin, a secondary metabolite isolated from fungi, is often used as a representative drug to reduce blood lipid concentration and treat hypercholesterolemia. Its structure is similar to that of HMG-CoA. Lovastatin inhibits the binding of the substrate to HMG-CoA reductase, and strongly competes with HMG-CoA reductase (HMGR), thereby exerting a hypolipidemic effect. Further, its safety has been confirmed in vivo and in vitro. Lovastatin also has anti-inflammatory, anti-cancer, and neuroprotective effects. Therefore, the biological activity of lovastatin, especially its anti-cancer effect, has garnered research attention. Several in vitro studies have confirmed that lovastatin has a significant inhibitory effect on cancer cell viability in a variety of cancers (such as breast, liver, cervical, lung, and colon cancer). At the same time, lovastatin can also increase the sensitivity of some types of cancer cells to chemotherapeutic drugs and strengthen their therapeutic effect. Lovastatin inhibits cell proliferation and regulates cancer cell signaling pathways, thereby inducing apoptosis and cell cycle arrest. This article reviews the structure, biosynthetic pathways, and applications of lovastatin, focusing on the anti-cancer effects and mechanisms of action.     

The Ganglioside GM3 Is Associated with Cisplatin-Induced Apoptosis in Human Colon Cancer Cells

Cisplatin (cis-diamminedichloroplatinum, CDDP) is a well-known chemotherapeutic agent for the treatment of several cancers. However, the precise mechanism underlying apoptosis of cancer cells induced by CDDP remains unclear. In this study, we show mechanistically that CDDP induces GM3-mediated apoptosis of HCT116 cells by inhibiting cell proliferation, and increasing DNA fragmentation and mitochondria-dependent apoptosis signals. CDDP induced apoptosis within cells through the generation of reactive oxygen species (ROS), regulated the ROS-mediated expression of Bax, Bcl-2, and p53, and induced the degradation of the poly (ADP-ribosyl) polymerase (PARP). We also checked expression levels of different gangliosides in HCT116 cells in the presence or absence of CDDP. Interestingly, among the gangliosides, CDDP augmented the expression of only GM3 synthase and its product GM3. Reduction of the GM3 synthase level through ectopic expression of GM3 small interfering RNA (siRNA) rescued HCT116 cells from CDDP-induced apoptosis. This was evidenced by inhibition of apoptotic signals by reducing ROS production through the regulation of 12-lipoxigenase activity. Furthermore, the apoptotic sensitivity to CDDP was remarkably increased in GM3 synthase-transfected HCT116 cells compared to that in controls. In addition, GM3 synthase-transfected cells treated with CDDP exhibited an increased accumulation of intracellular ROS. These results suggest the CDDP-induced oxidative apoptosis of HCT116 cells is mediated by GM3.     

p53 gene status and chemosensitivity in ovarian cancer.

Recent studies suggest that drug induced apoptosis relates to the sensitivity. p53 gene, which has a pivotal role in inducing apoptosis, frequently mutates in ovarian cancer. Therefore, p53 gene status and chemosensitivity in epithelial ovarian cancer is discussed. Nonresponders to chemotherapy had mutations of the p53 gene more frequently (83% for nonresponders vs. 16% for responders) in patients with epithelial ovarian cancer undergoing platinum-base chemotherapy. Apoptotic index was significantly greater in tumors with wild-type p53 gene than those without the gene. p53 gene transduction markedly enhanced the sensitivity to cisplatin (CDDP) and CDDP-induced apoptosis, but did not affect the sensitivity to paclitaxel (PTX) nor PTX-induced apoptosis in ovarian cancer cells without p53 gene. The combination treatment with a recombinant adenovirus carrying a wild-type p53 gene (AxCAp53) and CDDP significantly suppressed tumor growth of ovarian cancer cells with and without p53 gene, compared with a single treatment of either AxCAp53 or CDDP in ovarian cancer xenograft. Apoptotic index was significantly higher and proliferating cell nuclear antigen labeling index was relatively lower in an ovarian cancer xenograft without p53 gene receiving combination treatment, compared with a single treatment of either CDDP or AxCAp53, suggesting that the transduction of p53 gene induces apoptosis, but does not enhance the DNA repair system. A significant survival advantage was observed in the combination treatment compared with other treatments in carcinoma peritonitis models. In conclusion, p53 gene status contributes the sensitivity to CDDP in ovarian cancer. Additionally, combination treatment of p53 gene transduction and CDDP may be an effective therapeutic modality for ovarian cancer without wild-type p53 gene.     

Re-purposing clinical kinase inhibitors to enhance chemosensitivity by overriding checkpoints

Inhibitors of the DNA damage checkpoint kinase, Chk1, are highly effective as chemo- and radio-sensitizers in preclinical studies but are not well-tolerated by patients. We exploited the promiscuous nature of kinase inhibitors to screen 9 clinically relevant kinase inhibitors for their ability to sensitize pancreatic cancer cells to a sub-lethal concentration of gemcitabine. Bosutinib, dovitinib, and BEZ-235 were identified as sensitizers that abrogated the DNA damage checkpoint. We further characterized bosutinib, an FDA-approved Src/Abl inhibitor approved for chronic myelogenous leukemia. Unbeknownst to us, we used an isomer (Bos-I) that was unknowingly synthesized and sold to the research community as “authentic” bosutinib. In vitro and cell-based assays showed that both the authentic bosutinib and Bos-I inhibited DNA damage checkpoint kinases Chk1 and Wee1, with Bos-I showing greater potency. Imaging data showed that Bos-I forced cells to override gemcitabine-induced DNA damage checkpoint arrest and destabilized stalled replication forks. These inhibitors enhanced sensitivity to the DNA damaging agents’ gemcitabine, cisplatin, and doxorubicin in pancreatic cancer cell lines. The in vivo efficacy of Bos-I was validated using cells derived directly from a pancreatic cancer patient’s tumor. Notably, the xenograft studies showed that the combination of gemcitabine and Bos-I was significantly more effective in suppressing tumor growth than either agent alone. Finally, we show that the gatekeeper residue in Wee1 dictates its sensitivity to the 2 compounds. Our strategy to screen clinically relevant kinase inhibitors for off-target effects on cell cycle checkpoints is a promising approach to re-purpose drugs as chemosensitizers.     

5-Aminolevulinic Acid Protects against Cisplatin-Induced Nephrotoxicity without Compromising the Anticancer Efficiency of Cisplatin in Rats In Vitro and In Vivo

Background/Aims

Nephrotoxicity is a frequent and major limitation in cisplatin (CDDP)-based chemotherapy. 5-Aminolevulinic acid (ALA) is widely distributed in animal cells, and it is a precursor of tetrapyrole compounds such as heme that is fundamentally important in aerobic energy metabolism. The aim of this study is to evaluate the protective role of ALA in CDDP-induced acute kidney injury (AKI).

Method

We used CDDP-induced AKI rat model and cultured renal tubular cells (NRK-52E). We divided four groups of rats: control, CDDP only, CDDP + ALA(post);(ALA 10 mg/kg + Fe in drinking water) after CDDP, CDDP + ALA(pre & post).

Result

CDDP increased Cr up to 6.5 mg/dl, BUN up to 230 mg/dl, and ALA significantly reduced these changes. ALA ameliorates CDDP-induced morphological renal damages, and reduced tubular apoptosis evaluated by TUNEL staining and cleaved caspase 3. Protein and mRNA levels of ATP5α, complex(COX) IV, UCP2, PGC-1α in renal tissue were significantly decreased by CDDP, and ALA ameliorates reduction of these enzymes. In contrast, Heme Oxigenase (HO)-1 level is induced by CDDP treatment, and ALA treatment further up-regulates HO-1 levels. In NRK-52E cells, the CDDP-induced reduction of protein and mRNA levels of mitochondrial enzymes was significantly recovered by ALA + Fe. CDDP-induced apoptosis were ameliorated by ALA + Fe treatment. Furthermore, we evaluated the size of transplantated bladder carcinoma to the rat skin, and ALA did not change the anti cancer effects of CDDP.

Conclusion

These data suggested that the protective role of ALA in cisplatin-induced AKI is via protection of mitochondrial viability and prevents tubular apoptosis. Also there are no significant effects of ALA on anticancer efficiency of CDDP in rats. Thus, ALA has the potential to prevent CDDP nephrotoxicity without compromising its anticancer efficacy.     

Beclin 1 augmented cis-diamminedichloroplatinum induced apoptosis via enhancing caspase-9 activity

Beclin 1, identified as a Bcl-2-interacting protein, is known to enhance autophagy. However, the effect of Beclin 1 on apoptotic signaling has remained unclear. Here, we show that overexpression of Beclin 1 in MKN28 human gastric cancer cells augmented cis-diamminedichloroplatinum (CDDP)-induced apoptosis. Conversely, "knockdown" of Beclin 1 by a small inhibitory RNA in MKN 1 cells attenuated this cytotoxicity. Furthermore, not only caspase-3/7 activities, but also caspase-9 activity was increased in Beclin 1 gene transfectants treated with CDDP, and caspase-9 inhibitor completely abolished augmentation of CDDP-induced apoptosis by Beclin 1 as did a caspase-3 inhibitor. Thus, Beclin 1 augments CDDP-induced apoptosis through enhancing caspase-9 activity and functions as a pro-apoptotic molecule.     

下调TSG101基因对人急性髓性白血病细胞的调节作用

构建肿瘤易感基因101(TSG101)基因的小干扰RNA载体并将其转导入HL-60细胞,获得稳定转染的阳性克隆后,应用RT-PCR和Western印迹进行鉴定;MTT法和流式细胞仪检测细胞转染前后生长速度和细胞周期的变化;DNA梯带(ladder)法和流式细胞仪检测细胞对顺铂诱导的凋亡的变化;Western印迹检测耐药相关蛋白P-gp和MRP的表达变化。结果表明,成功构建了TSG101的小干扰RNA载体;经蛋白质水平检测证实成功建立了稳定的TSG101低表达的白血病细胞模型;转染TSG101小干扰RNA后的细胞生长速度显著减慢,出现G1期阻滞;对顺铂的敏感性明显增强,形成DNA条带,且低表达P-gp。因此,下调TSG101基因能抑制HL-60细胞生长,增加细胞对化疗药物的敏感性,并提示该基因具有进行白血病基因治疗的可行性。     

Lovastatin inhibits bone marrow-derived dendritic cell maturation and upregulates proinflammatory cytokine production

Statins are a group of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors which are most effective as lipid lowering agents, and are currently extensively used clinically. Recently, it was also shown that statins affect the immune response. We investigated the effects of lovastatin on the maturation and functional changes of bone marrow-derived dendritic cells (BM-DC). Lovastatin inhibited MHC class II and CD40 expression on DC in a dose-dependent manner, but had lesser effects on CD16, CD80, CD86, and CD11b expression. Nuclear extracts of lovastatin treated DC had decreased NF-kappaB DNA binding activity. Although antigen capture capacity of DC was not affected by lovastatin, the T-cell stimulatory activity of DC was inhibited. Lovastatin up-regulated DC pro-inflammatory cytokine production induced by LPS as measured by intracellular cytokine staining, ELISA and cDNA microarrays. Mevalonate, added in vitro, prevented these effects. These results indicate that lovastatin may inhibit BM-DC maturation and up-regulate cytokine production through a mevalonate dependent pathway, and may cause adverse effects on either innate or adaptive immunity.     

Functional and physical interactions between ERCC1 and MSH2 complexes for resistance to cis-diamminedichloroplatinum(II) in mammalian cells

Bulky DNA lesions are mainly repaired by nucleotide excision repair (NER), in which the interaction of ERCC1 with XPA protein recruits the ERCC1-XPF complex, which acts as a structure-specific endonuclease in the repair process. However, additional functions besides NER have been suggested for the ERCC1-XPF complex, because ERCC1- or XPF-deficient rodent cells are significantly more sensitive to DNA interstrand cross-linking (ICL) agents such as cis-diamminedichloroplatinum(II) (CDDP) than any other NER-deficient cells and because ERCC1-deficient mice suffer a more severe phenotype than XPA-deficient mice. By using RNA interference we show here that suppression of ERCC1 expression increases the sensitivity of xeroderma pigmentosum group A (XPA)-deficient human cells to CDDP but not to UV. This increased sensitivity to CDDP is observed in mouse cells defective in Xpa as well but not in cells defective both in Xpa and the mismatch repair gene Msh2. These data suggest that ERCC1 and MSH2 are involved co-operatively in CDDP resistance in mammalian cells. As a possible molecular basis, we show further a physical interaction between endogenous ERCC1 and MSH2 complexes in HeLa cell extracts. Using tagged ERCC1 in COS7 cells, the minimum region in ERCC1 necessary for the immuno-precipitation of MSH2 is turned out to be the carboxyl-terminal domain between the 184th and 260th amino acid, which is partly overlapping with the XPF-binding domain of ERCC1. This interaction may be important in additional functions of ERCC1-XPF including the repair of CDDP-induced DNA damage.     

Enhanced Sensitivity of G1 Arrested Human Cancer Cells Suggests a Novel Therapeutic Strategy Using a Combination of Simvastatin and TRAIL

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) preferentially induces apoptosis in tumor cells over normal cells. To study the relationship between cell cycle progression and TRAIL-induced apoptosis, SW480 colon cancer and H460 lung cancer cell lines were examined for their sensitivity to TRAIL after arrest in different cell cycle phases. Cells were synchronized in G0/G1, S, and G2/M phase by serum starvation, aphidicolin, or nocodazole treatment, respectively. We found that arrest of cells in G0/G1 phase confers significantly higher susceptibility to TRAIL-induced apoptosis as compared to cells in late G1, S, or G2/M phase. To determine if cell cycle phase could be harnessed for therapeutic gain in the presence of TRAIL, we used the HMG-CoA reductase inhibitor, Simvastatin and lovastatin, to enrich a cancer cell population in G0/G1. Both simvastatin and lovastatin significantly augmented TRAIL-induced apoptosis in tumor cells, but not in normal keratinocytes. The results indicate that TRAIL, in combination with a HMG-CoA reductase inhibitor, may have therapeutic potential in the treatment of human cancer.

Key Words

TRAIL, Synchronization, Simvastatin, Cancer Therapy, Lovastatin, Cell Cycle, Apoptosis     

Differential Regulation of c-Jun Protein Plays an Instrumental Role in Chemoresistance of Cancer Cells

The chemotherapeutic drug cisplatin (cis-diamminedichloroplatinum(II) (CDDP)) is widely used in the treatment of human cancers. However, the mechanism underlying intrinsic tumor resistance to CDDP remains elusive. Here, we demonstrate that treatment with CDDP resulted in down-regulation of c-Jun expression via caspase-9-dependent cleavage of c-Jun at Asp-65 and MEKK1-mediated ubiquitylation and degradation of c-Jun in CDDP-sensitive cancer cells. In contrast, activation of JNK2 (but not JNK1) phosphorylated and up-regulated the expression of c-Jun in CDDP-resistant cells. Activated c-Jun bound to the promoter regions of the MDR1 gene and promoted the expression of MDR1. Expression of a cleavage-resistant c-Jun mutant (D65A) suppressed CDDP-induced apoptosis of CDDP-sensitive cells, whereas depletion of JNK2, c-Jun, or MDR1 in CDDP-resistant cancer cells promoted apoptosis upon CDDP treatment. In addition, mammary gland tumors induced by polyomavirus middle T antigen in JNK2^−/− mice were more sensitive to CDDP compared with those in JNK2^+/+ mice. These findings highlight the instrumental role of c-Jun in the resistance of tumors to treatment with CDDP and indicate that c-Jun is a molecular target for improving cancer therapy.     

MK2206 Enhances Cisplatin-Induced Cytotoxicity and Apoptosis in Testicular Cancer Through Akt Signaling Pathway Inhibition

OBJECTIVE: To improve conventional chemotherapeutic efficacy, it is significant to identify novel molecular markers for chemosensitivity as well as possible molecules accelerating cell-killing mechanisms. In this study, we attempted to elucidate how MK2206, an allosteric Akt inhibitor, enhances the cisplatin (CDDP)-induced cytotoxicity and apoptosis in testicular cancer. MATERIALS AND METHODS: We checked three testicular cancer cell lines for the expression of phospho(p)-Akt and its downstream molecules targets by Western blot. The potential antitumor effects were analyzed by MTT assay in vitro and by subcutaneous xenograft models in vivo. The cell invasion was analyzed by transwell invasion assay, and the activities of Akt signaling pathway and expression of apoptosis-related proteins were measured by Western blot. RESULTS: Our results indicated that there was overactivation of p-Akt and its downstream molecules in testicular cancer cell lines compared with normal testis epithelium cells. MK2206 (600 nM) inhibited cell invasion in TCAM-2 and P19 cell lines and significantly increased the susceptibility of testicular cancer to CDDP. Combined with CDDP, MK2206 potentiated CDDP-induced cytotoxicity and apoptosis, with repressed expression of p-Akt and its downstream targets. The subcutaneous xenograft models also showed that a combined CDDP/MK2206 therapy completely suppressed tumor growth without any side effects. CONCLUSION: These results suggested that the concomitant use of MK2206 could enhance the CDDP-induced cytotoxicity and apoptosis in testicular cancer with the suppressed expression of Akt pathway.     

Management of Oxidative Stress by Heme Oxygenase-1 in Cisplatin-induced Toxicity in Renal Tubular Cells

Induction of heme oxygenase-1 (HO-1) may serve as an immediate protective response during treatment with the cytostatic drug cisplatin (CDDP). Oxidative pathways participate in the characteristic nephrotoxicity of CDDP. In the present study, cultured tubular cells (LLC-PK1) were used to investigate whether induction of HO provided protection against CDDP by maintaining the cellular redox balance. The antioxidants, &#102 -tocopherol (TOCO) and N -acetylcysteine (NAC), were used to demonstrate that elevation of ROS levels contribute to the development of CDDP-induced cytotoxicity. Chemical modulators of HO activity were used to investigate the role of HO herein. Hemin was used to specifically induce HO-1, while exposure of the cells to tin-protoporphyrin (SnPP) was shown to inhibit HO activity. Hemin treatment prior to CDDP-exposure significantly decreased the generation of ROS to control levels, while inhibition of HO increased the ROS levels beyond the levels measured in cells treated with CDDP alone. Furthermore, HO induction protected significantly against the cytotoxicity of CDDP, although this protection was limited. Similar results were obtained when the cells were preincubated with TOCO, suggesting that mechanisms other than impairment of the redox ratio are important in CDDP-induced loss of cell viability in vitro. In addition, SnPP treatment exacerbated the oxidative response and cytotoxicity of CDDP, especially at low CDDP concentrations. We therefore conclude that HO is able to directly limit the CDDP-induced oxidative stress response and thus serves as safeguard of the cellular redox balance.     

A combination of cilostazol and Ginkgo biloba extract protects against cisplatin-induced Cochleo-vestibular dysfunction by inhibiting the mitochondrial apoptotic and ERK pathways

Cisplatin (cis-diammine-dichloroplatinum; CDDP) is an anticancer drug that induces significant hearing loss and balance dysfunction as side effects. Cilostazol (CS, 6-[4-(1-cyclohexyl-1H-tetrazol-5-yl) butoxy]-3, 4-dihydro-2-(1H)-quinolinone) has neuroprotective and antioxidant effects, whereas Ginkgo biloba extract (GbE) has preventive effects on CDDP-induced hearing loss in rats, and GbE enhances the antiatherogenic effect of CS by inhibiting the generation of reactive oxygen species (ROS). The purpose of this study was to investigate the effects of renexin (RXN), which contains GbE and CS, against CDDP-induced cochleo-vestibular dysfunction in rats and to elucidate the mechanism underlying the protective effects of RXN on auditory cells. Rats intraperitoneally injected with CDDP exhibited an increase in hearing threshold and vestibular dysfunction, which agreed with hair cell damage in the Organ of Corti and otoliths. However, these impairments were significantly prevented in a dose-dependent manner by pre- and co-treatment with RXN, and these preventive effects in RXN-treated rats were more prominent than those in GbE-treated rats. In a CDDP pharmacokinetic study, platinum concentration was very similar between CDDP-only treated and RXN+CDDP cotreated rats. RXN markedly attenuated CDDP-induced intracellular ROS and significantly reduced CDDP-activated expression of p-extracellular regulated kinase (ERK), BAX, cytochrome c, cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase, but increased BCL-XL expression. These results show that RXN may have a synergistic effect by strongly protecting hearing and vestibular dysfunction induced by CDDP by inhibiting ROS production, mitochondrial pathways and the ERK pathway, without interfering with CDDP pharmacokinetics. Therefore, RXN could potentially be used to reduce CDDP-related hearing loss and dizziness.     

Characterization of lovastatin–docosahexaenoate anticancer properties against breast cancer cells

Lovastatin (LOV) and docosahexaenoic acid (DHA), besides improving cardiovascular functions, are also known for their anticancer activities. However, use of these compounds for treating or preventing cancer is limited because of their efficacies. The approach pursued involved chemical linkage of these two chemotypes. A lovastatin–docosahexaenoate (LOV–DHA) conjugate was prepared and tested against selected breast tumor cells lines with differential expression of estrogen receptors (ER) and Heregulin-2 (Her-2). The LOV–DHA conjugate exhibited superior cytotoxic effects against ER⁻/Her-2⁻ cell lines (MDA-MB-231 and MDA-MB-468), which were not observed with DHA or lovastatin alone, or in combination. Lovastatin supplementation arrested cells in the G₀/G₁ phase and enhanced expression levels of p21, whereas the conjugate did not demonstrate cell cycle arrest nor increased p21 expression. The LOV–DHA conjugate induced significant (P < 0.05) apoptosis as low as 1 μM, whereas DHA and lovastatin were ineffective at this concentration. The growth inhibitory effects of lovastatin were reversed by the addition of mevalonate, whereas mevalonate had no effect on the LOV–DHA conjugate-induced growth inhibition in MDA-MB-231 cells. Furthermore, the LOV–DHA conjugates were stable in mouse serum and intracellularly in MDA-MB-231 cells. These data suggest that the LOV–DHA conjugate mediated its effects through a HMG-CoA reductase-independent pathway and exerted significantly (P < 0.05) higher anticancer effects in breast cancer cells than lovastatin or DHA alone.     

Studies on mutagenesis and repair induced by platinum analogs

Mutagenesis and cytotoxicity were studied in Escherichia coli by iproplatin and carboplatin, two analogs of cisplatin (CDDP) currently undergoing clinical trial. As with CDDP, mutagenesis by these agents was mediated by the umuDC gene product. In contrast to CDDP, however, mismatch repair did not substantially contribute to survival of cells after exposure to these agents since dam-3 E. coli were not more sensitive than wild type E. coli. UvrA- E. coli, however were more sensitive to these analogs demonstrating that as with CDDP, uvr endonuclease-mediated excision contributes to the repair of DNA damage induced by platinum compounds.