Hypothalamic Proline Rich Polypeptide Regulates Hematopoiesis

The AGAPEPAEPAQPGVY proline-rich polypeptide (PRP-1) was isolated from neurosecretory granules of the bovine neurohypophysis; it is produced by N. supraopticus and N. paraventricularis. It has been shown that PRP-1 has many potentially beneficial biological effects including immunoregulatory, hematopoietic, antimicrobial and anti-neurodegenerative properties. Here we demonstrated that PRP-1 administration influence on redistribution of monocytes, granulocytes and lymphocytes between bone marrow (BM) and peripheral blood and promotes the influx of granulocytes and monocytes/macrophages from BM into peripheral blood and accumulation of immature granulocyte and monocyte in BM and delayed the maturation of T cells in BM. PRP-1 increased colony-forming cell proliferation in rat cells in vivo. In PRP-treated rat BM, the CFU number at day 4, 7 and 14 was considerably increased in comparison with untreated rats BM and no difference was found at day 21 and day 28. We found that PRP-1 enhances erythroid and myeloid colonies formation in human CD34⁺ progenitor cell culture in the presence of different growth factors and down-regulates T cells colony formation and specific surface markers expression during induction of human CD34⁺ progenitor cells differentiation into T lymphocytes lineage. We suggested that the hypothalamic PRP-1 possibly represents an endogenous peptide whose primary functions are to regulate neuronal survival and differentiation and hematopoiesis within neurosecretory hypothalamus—bone marrow humoral axis.     

Melatonin as an effective protector against doxorubicin-induced cardiotoxicity

The present study was designed to explore the protective effects of melatonin and its analogs, 6-hydroxymelatonin and 8-methoxy-2-propionamidotetralin, on the survival of doxorubicin-treated mice and on doxorubicin-induced cardiac dysfunction, ultrastructural alterations, and apoptosis in mouse hearts. Whereas 60% of the mice treated with doxorubicin (25 mg/kg ip) died in 5 days, almost all the doxorubicin-treated mice survived when melatonin or 6-hydroxymelatonin (10 mg/l) was administered in their drinking water. Perfusion of mouse hearts with 5 microM doxorubicin for 60 min led to a 50% suppression of heart rate x left ventricular developed pressure and a 50% reduction of coronary flow. Exposure of hearts to 1 microM melatonin or 6-hydroxymelatonin reversed doxorubicin-induced cardiac dysfunction. 8-Methoxy-2-propionamidotetralin had no protective effects on animal survival and on in vitro cardiac function. Infusion of melatonin or 6-hydroxymelatonin (2.5 microg/h) significantly attenuated doxorubicin-induced cardiac dysfunction, ultrastructural alterations, and apoptosis in mouse hearts. Neither melatonin nor 6-hydroxymelatonin compromised the antitumor activity of doxorubicin in cultured PC-3 cells. These results suggest that melatonin protect against doxorubicin-induced cardiotoxicity without interfering with its antitumor effect.     

HSP25 down-regulation enhanced p53 acetylation by dissociation of SIRT1 from p53 in doxorubicin-induced H9c2 cell apoptosis

Heat shock proteins (HSPs) play important roles in cellular stress resistance. Previous reports had already suggested that HSP27 played multiple roles in preventing doxorubicin-induced cardiotoxicity. Although HSP25 might have biological functions similar to its human homolog HSP27, the mechanism of HSP25 is still unclear in doxorubicin-induced cardiomyocyte apoptosis. To investigate HSP25 biological function on doxorubicin-induced apoptosis, flow cytometry was employed to analyze cell apoptosis in over-expressing HSP25 H9c2 cells in presence of doxorubicin. Unexpectedly, the H9c2 cells of over-expressing HSP25 have no protective effect on doxorubicin-induced apoptosis. Moreover, no detectable interactions were detected by coimmunoprecipitation between HSP25 and cytochrome c, and HSP25 over-expression failed in preventing cytochrome c release induced by doxorubicin. However, down-regulation of endogenous HSP25 by a specific small hairpin RNA aggravates apoptosis in H9c2 cells. Subsequent studies found that HSP25, but not HSP90, HSP70, and HSP20, interacted with SIRT1. Knockdown of HSP25 decreased the interaction between SIRT1 and p53, leading to increased p53 acetylation on K379, up-regulated pro-apoptotic Bax protein expression, induced cytochrome c release, and triggered caspase-3 and caspase-9 activation. These findings indicated a novel mechanism by which HSP25 regulated p53 acetylation through dissociation of SIRT1 from p53 in doxorubicin-induced H9c2 cell apoptosis.     

Coadministration of swainsonine and doxorubicin attenuates doxorubicin-induced lethality in mice.

This study in mice concerns the protective effectiveness and mechanisms of action by which a coadministered regimen of an immunomodulatory alkaloid swainsonine (8alphabeta-indolizidine-1alpha,2alpha,8beta-triol) protects against lethality induced by a single bolus intraperitoneal injection of LD50/14 doxorubicin. This swainsonine coadministration treatment regimen has been identified previously in our laboratory as the superior of the two optimal conditions for diminishing lethality in mice due to LD50/14 doxorubicin. The anthracycline, doxorubicin is a potent and widely used cancer chemotherapeutic agent whose clinical usefulness is limited by both a dose- and time-dependent cardiomyopathy. Specifically, mice were given simultaneous injections of swainsonine or its diluent buffer, phosphate buffered saline and LD50/14 doxorubicin on day 0, followed by twice daily injections of swainsonine or phosphate buffered saline up to day +9. The survival and well being of mice were monitored daily for 70 days, which may be considered equivalent to a period of 4 to 5 years in humans. This duration has a clinical implication with respect to the late manifestation of cardiotoxicity after doxorubicin treatment. We quantified the bone marrow cellularity of mice and performed in vitro progenitor cell assays to determine the effects of swainsonine coadministration treatment regimen on bone marrow competence after doxorubicin treatment. The effects of this regimen on doxorubicin-induced changes in heart morphology and on hematologic toxicities caused by doxorubicin were determined. This swainsonine coadministration treatment regimen significantly diminished doxorubicin-induced lethality and prolonged survival and well being of mice by preventing bone marrow pancytopenia from the start of therapy. It decreased bone marrow toxicity and facilitated its restoration. It accelerated restoration of blood hematocrit and total leukocyte levels. Also it facilitated the proliferation and differentiation of bone marrow pluripotent stem cells along the different paths to progenitor lineages, and significantly preserved the mouse heart morphology. These underlying mechanisms of action for the protection by swainsonine coadministration strongly suggest a potential role for swainsonine in high dose chemotherapy with doxorubicin.     

Overexpression of Nd1, a novel Kelch family protein, in the heart of transgenic mice protects against doxorubicin-induced cardiomyopathy

Doxorubicin is one of the most effective drugs available for cancer chemotherapy. However, the clinical use of doxorubicin has been greatly limited because of severe side effects on cardiomyocytes. Since Nd1-L, a novel actin-binding protein, is expressed most abundantly in the heart of adult mice, we examined a role of Nd1-L in doxorubicin-induced cardiomyopathy. When doxorubicin (5 mg/kg × 4 times) was injected into adult mice at a 3-day-interval, approximately 50% of injected mice died within 4 weeks of the first injection. Nd1-L mRNA expression in the heart decreased within 3 weeks after the first injection and many cardiomyocytes of injected mice died by apoptosis. Overexpression of Nd1-L in the heart of transgenic mice protected the cardiomyocytes from apoptosis and improved survival rate after doxorubicin injection. Furthermore, activation of Erk1/2 was observed in cultured cells overexpressing Nd1-L. Thus, Nd1-L plays a critical role in protecting the heart from doxorubicin-induced cardiomyopathy.     

Upregulation of IGF-IIRα intensifies doxorubicin-induced cardiac damage

Cardiotoxicity by doxorubicin hampers its therapeutic potential as an anticancer drug, but mechanisms leading to cardiotoxicity remain contentious. Through this study, the functional contribution of insulin-like growth factor receptor type II α (IGF-IIRα) which is a novel stress-inducible protein was explored in doxorubicin-induced cardiac stress. Employing both in vitro H9c2 cells and in vivo transgenic rat models (SD-TG [IGF-IIRα]) overexpressing IGF-IIRα specifically in heart, we found that IGF-IIRα leads to cardiac structural abnormalities and functional perturbations that were severely aggravated by doxorubicin-induced cardiac stress. Overexpression of IGF-IIRα leads to cumulative elevation of stress associated cardiac hypertrophy and apoptosis factors. There was a significant reduction of survival associated proteins p-Akt and estrogen receptor β/α, and abnormal elevation of cardiac hypertrophy markers such as atrial natriuretic peptide, cardiac troponin-I, and apoptosis-inducing agents such as p53, Bax, and cytochrome C, respectively. IGF-IIRα also altered the expressions of AT1R, ERK1/2, and p38 proteins. Besides, IGF-IIRα also increased the reactive oxygen species production in H9c2 cells which were markedly aggravated by doxorubicin treatment. Together, we showed that IGF-IIRα is a novel stress-induced protein that perturbed cardiac homeostasis and cumulatively exacerbated the doxorubicin-induced cardiac injury that perturbed heart functions and ensuing cardiomyopathy.     

Essential role for integrin linked kinase in Akt-mediated integrin survival signaling in hippocampal neurons

Activation of integrin receptors in neurons can promote cell survival and synaptic plasticity, but the underlying signal transduction pathway(s) is unknown. We report that integrin signaling prevents apoptosis of embryonic hippocampal neurons by a mechanism involving integrin-linked kinase (ILK) that activates Akt kinase. Activation of integrins using a peptide containing the amino acid sequence EIKLLIS derived from the alpha chain of laminin protected hippocampal neurons from apoptosis induced by glutamate or staurosporine, and increased Akt activity in a beta1 integrin-dependent manner. Transfection of neurons with a plasmid encoding dominant negative Akt blocked the protective effect of the integrin-activating peptide, as did a chemical inhibitor of Akt. Although inhibitors of phosphoinositide-3 (PI3) kinase blocked the protective effect of the peptide, we found no increase in PI3 kinase activity following integrin stimulation suggesting that PI3 kinase was necessary for Akt activity but was not sufficient for the increase in Akt activity following integrin activation. Instead, we show a requirement for ILK in integrin receptor-induced Akt activation. ILK was activated following integrin stimulation and dominant negative ILK blocked integrin-mediated Akt activation and cell survival. Activation of ILK and Akt were also required for neuroprotection by substrate-associated laminin. These results establish a novel pathway that signals cell survival in neurons in response to integrin receptor activation.     

The Role of Kif4A in Doxorubicin-Induced Apoptosis in Breast Cancer Cells

This study was to investigate the mechanism and role of Kif4A in doxorubicin-induced apoptosis in breast cancer. Using two human breast cancer cell lines MCF-7 (with wild-type p53) and MDA-MB-231 (with mutant p53), we quantitated the expression levels of kinesin super-family protein 4A (Kif4A) and poly (ADP-ribose) Polymerase-1 (PARP-1) by Western blot after doxorubicin treatment and examined the apoptosis by flow cytometry after treatment with doxorubicin and PARP-1 inhibitor, 3-Aminobenzamide (3-ABA). Our results showed that doxorubicin treatment could induce the apoptosis of MCF-7 and MDA-MB-231 cells, the down-regulation of Kif4A and upregulation of poly(ADP-ribose) (PAR). The activity of PARP-1 or PARP-1 activation was significantly elevated by doxorubicin treatment in dose- and time-dependent manners (P < 0.05), while doxorubicin treatment only slightly elevated the level of cleaved fragments of PARP-1 (P > 0.05). We further demonstrated that overexpression of Kif4A could reduce the level of PAR and significantly increase apoptosis. The effect of doxorubicin on apoptosis was more profound in MCF-7 cells compared with MDA-MB-231 cells (P < 0.05). Taken together, our results suggest that the novel role of Kif4A in doxorubicin-induced apoptosis in breast cancer cells is achieved by inhibiting the activity of PARP-1.     

Melatonin attenuates doxorubicin-induced cardiotoxicity through preservation of YAP expression

There are increasing concerns related to the cardiotoxicity of doxorubicin in the clinical setting. Recently, melatonin has been shown to exert a cardioprotective effect in various cardiovascular diseases, including cardiotoxic conditions. In this study, we examined the possible protective effects of melatonin on doxorubicin-induced cardiotoxicity and explored the underlying mechanisms related to this process. We found that in vitro doxorubicin treatment significantly decreased H9c2 cell viability and induced apoptosis as manifested by increased TUNEL-positive cells, down-regulation of anti-apoptotic protein Bcl-2, as well as up-regulation of pro-apoptotic protein Bax. This was associated with increased reactive oxygen species (ROS) levels and decreased mitochondrial membrane potentials (MMP). In vivo, five weeks of doxorubicin treatment significantly decreased cardiac function, as evaluated by echocardiography. TUNEL staining results confirmed the increased apoptosis caused by doxorubicin. On the other hand, combinational treatment of doxorubicin with melatonin decreased cardiomyocyte ROS and apoptosis levels, along with increasing MMP. Such doxorubicin-melatonin co-treatment alleviated in vivo doxorubicin-induced cardiac injury. Western Blots, along with in vitro immunofluorescence and in vivo immunohistochemical staining confirmed that doxorubicin treatment significantly down-regulated Yes-associated protein (YAP) expression, while YAP levels were maintained under co-treatment of doxorubicin and melatonin. YAP inhibition by siRNA abolished the protective effects of melatonin on doxorubicin-treated cardiomyocytes, with reversed ROS level and apoptosis. Our findings suggested that melatonin treatment attenuated doxorubicin-induced cardiotoxicity through preserving YAP levels, which in turn decreases oxidative stress and apoptosis.     

Augmentation of myelopoiesis in a murine host bearing a T cell lymphoma following in vivo administration of proton pump inhibitor pantoprazole

Proton pump inhibitors (PPI) are being proposed as potent antitumor agents, owing to their ability to specifically induce tumor cell death by reversing H⁺ ion homeostasis. As tumor growth induces myelosuppression in tumor-bearing hosts, it remains unclear if PPI can also modulate tumor-induced myelosuppression. Thus, we studied the effect of in vivo administration of pantoprazole (PPZ), a PPI, on myelopoiesis in a murine model of a transplantable T cell lymphoma, designated as Dalton’s lymphoma (DL). Intraperitoneal administration of PPZ to tumor-bearing mice resulted in an enhanced bone marrow cellularity, inhibited induction of apoptosis and augmented bone marrow cell (BMC) survival. BMC of PPZ-administered tumor-bearing mice showed elevated number of F4/80 positive cells, augmented colony forming ability and differentiation in bone marrow-derived macrophages (BMDM) with higher expression of F4/80 and CD11c markers. This study also presents evidences to indicate that PPZ-dependent augmentation of myelopoiesis in the tumor-bearing host is dependent on an enhanced expression of M-CSF and receptors for M-CSF & GM-CSF in BMC, along with a modulation in the expression of cell survival regulatory molecules PUMA, Bcl2, p53 and caspase-activated DNase (CAD). BMDM obtained from PPZ-administered tumor-bearing mice also showed an augmented expression of TLR-2, tumoricidal activity, production of NO and monokines: IL-1, IL-6 & TNF-α. The study discusses the possible mechanisms underlying PPZ-dependent augmentation of myelopoiesis. Taken together, the present study proposes that a PPZ-dependent alleviation of tumor-induced myelosuppression could contribute to an augmented myelopoiesis.     

α2β1 integrin promotes chemoresistance against doxorubicin in cancer cells through extracellular signal-regulated kinase (ERK)

The role and the mechanisms by which β1 integrins regulate the survival and chemoresistance of T cell acute lymphoblastic leukemia (T-ALL) still are poorly addressed. In this study, we demonstrate in T-ALL cell lines and primary blasts, that engagement of α2β1 integrin with its ligand collagen I (ColI), reduces doxorubicin-induced apoptosis, whereas fibronectin (Fn) had no effect. ColI but not Fn inhibited doxorubicin-induced mitochondrial depolarization, cytochrome c release, and activation of caspase-9 and -3. ColI but not Fn also prevented doxorubicin from down-regulating the levels of the prosurvival Bcl-2 protein family member Mcl-1. The effect of ColI on Mcl-1 occurred through the inhibition of doxorubicin-induced activation of c-Jun N-terminal kinase (JNK). Mcl-1 knockdown experiments showed that the maintenance of Mcl-1 levels is essential for ColI-mediated T-ALL cell survival. Furthermore, activation of MAPK/ERK, but not PI3K/AKT, is required for ColI-mediated inhibition of doxorubicin-induced JNK activation and apoptosis and for ColI-mediated maintenance of Mcl-1 levels. Thus, our study identifies α2β1 integrin as an important survival pathway in drug-induced apoptosis of T-ALL cells and suggests that its activation can contribute to the generation of drug resistance.     

Hyaluronidase activation of c-Jun N-terminal kinase is necessary for protection of L929 fibrosarcoma cells from staurosporine-mediated cell death

Hyaluronidase counteracts the growth inhibitory function of transforming growth factor beta (TGF-beta), whereas secretion of autocrine TGF-beta and hyaluronidase is necessary for progression and metastasis of various cancers. Whether hyaluronidase and TGF-beta1 induce resistance to staurosporine in L929 fibrosarcoma cells was investigated. When pretreated with TGF-beta1 for 1-2 h, L929 cells resisted staurosporine apoptosis. In contrast, without pretreatment, hyaluronidase protected L929 cells fromstaurosporine apoptosis. Hyaluronidase rapidly activated p42/44 MAPK (or ERK) in L929 cells and TGF-beta1 retarded the activation. Nonetheless, TGF-beta1 synergistically increased hyaluronidase-mediated inhibition of staurosporine apoptosis. Hyaluronidase rapidly activated c-Jun N-terminal kinase (JNK1 and JNK2) in L929 cells in 20 min. Dominant negative JNK1, JNK2, and JNK3 abolished the hyaluronidase inhibition of staurosporine apoptosis, but not the TGF-beta1 protective effect. Unlike the resistance to staurosporine, pretreatment of L929 cells with hyaluronidase is necessary to generate resistance to other anticancer drugs, including doxorubicin, daunorubicin, actinomycin D, and camptothecin, and the induced resistance was also blocked by dominant-negative JNKs. Together, hyaluronidase-mediated JNK activation is necessary to generate resistance to various anticancer drugs in L929 cells.     

Proline-rich Polypeptide-1 Protects the Cells In Vitro from Genotoxic Effects of Mitomycin C

A new proline-rich polypeptide (PRP-1) has been earlier shown to possess a broad spectrum of biological activities and seems to be a potential medicine. The potential genotoxic properties of PRP-1 and protective effect of PRP-1 against genotoxic action of Mitomycin C (MMC) were analyzed in details in the present work. DNA and chromosome damages were studied in KCL-22 cell line of human myeloid leukemia by the Comet assay and micronucleus induction test, respectively. The results suggest that DNA damages are, at least partly, transient and reparable. PRP-1 at the doses 0.5–2.0 μg/ml does not possess genotoxic activity. Moreover, this peptide expresses both preventive and therapeutic effects against MMC-induced DNA damage. Pre-treatment of cells with PRP-1 also prevents the appearance of daughter cells bearing as heavy MMC-induced DNA/chromosome damages as MNs. Thus, the polypeptide studied is able to protect the cells from genotoxic action of MMC. This defense includes not only DNA but also heritable chromosome damage in post-mitotic cells. Possible mechanisms of PRP-1 protective action are discussed.     

Proline-Rich Polypeptide-1 Protects the Cells In Vitro from Genotoxic Effects of Mitomycin C

A new proline-rich polypeptide (PRP-1) has been earlier shown to possess a broad spectrum of biological activities and seems to be a potential medicine. The potential genotoxic properties of PRP-1 and protective effect of PRP-1 against genotoxic action of Mitomycin C (MMC) were analyzed in details in the present work. DNA and chromosome damages were studied in KCL-22 cell line of human myeloid leukemia by the Comet assay and micronucleus induction test, respectively. The results suggest that DNA damages are, at least partly, transient and reparable. PRP-1 at the doses 0.5–2.0 l g/ml does not possess genotoxic activity. Moreover, this peptide expresses both preventive and therapeutic effects against MMCinduced DNA damage. Pre-treatment of cells with PRP-1 also prevents the appearance of daughter cells bearing as heavy MMC-induced DNA/chromosome damages as MNs. Thus, the polypeptide studied is able to protect the cells from genotoxic action of MMC. This defense includes not only DNA but also heritable chromosome damage in postmitotic cells. Possible mechanisms of PRP-1 protective action are discussed.     

Mice primed with swainsonine are protected against doxorubicin-induced lethality.

The anthracycline, doxorubicin is a potent cancer chemotherapeutic agent whose therapeutic usefulness is limited by both a dose- and time-dependent cardiomyopathy. We tested the ability of an immunomodulatory alkaloid swainsonine (8alphabeta-indolizidine-1alpha,2alpha,8beta-triol) to protect C57BL/6 mice against lethality within 70 days following a single bolus intraperitoneal injection of LD50/14 doxorubicin. Also, we sought the potential mechanisms responsible for this protection. This extended 70-day study in mice, which may be considered equivalent to a period of 4 to 5 years in humans, has clinical implication for delayed cardiotoxic sequela of therapy with high dose doxorubicin. Mice were pretreated with swainsonine or its diluent buffer, phosphate buffered saline for ten consecutive days prior to a single bolus intraperitoneal injection of a LD50/14 doxorubicin. We have previously defined this swainsonine pretreatment regimen as one of the two optimal conditions for swainsonine rescue of mice from death induced by LD50/14 doxorubicin. The survival and well being of groups of mice pretreated with swainsonine and phosphate buffered saline prior to LD50/14 doxorubicin, sham-treated and untreated were monitored daily for up to 70 days. The bone marrow cellularity of the mice were quantified, and in vitro progenitor cell assays were used to determine the effects of these treatment regimens on bone marrow competence following doxorubicin treatment. The effects of these treatment regimens on heart morphology and hematologic toxicities were also determined. This swainsonine pretreatment regimen significantly abrogated doxorubicin-induced lethality and prolonged survival of mice by facilitating restoration of bone marrow cellularity, accelerating restoration of blood hematocrit and total leukocyte levels, enhancing the proliferation and differentiation of bone marrow pluripotent stem cells along the different paths to progenitor lineages, and preserving the heart morphology. This study strongly suggests a potential role for swainsonine with doxorubicin in cancer chemotherapy.     

N1-guanyl-1,7-diaminoheptane (GC7) enhances the therapeutic efficacy of doxorubicin by inhibiting activation of eukaryotic translation initiation factor 5A2 (eIF5A2) and preventing the epithelial–mesenchymal transition in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) cells undergo the epithelial–mesenchymal transition (EMT) during chemotherapy, which reduces the efficacy of doxorubicin-based chemotherapy. We investigated N1-guanyl-1,7-diaminoheptane (GC7) which inhibits eukaryotic translation initiation factor 5A2 (eIF5A2) activation; eIF5A2 is associated with chemoresistance. GC7 enhanced doxorubicin cytotoxicity in epithelial HCC cells (Huh7, Hep3B and HepG2) but had little effect in mesenchymal HCC cells (SNU387, SNU449). GC7 suppressed the doxorubicin-induced EMT in epithelial HCC cells; knockdown of eIF5A2 inhibited the doxorubicin-induced EMT and enhanced doxorubicin cytotoxicity. GC7 combination therapy may enhance the therapeutic efficacy of doxorubicin in HCC by inhibiting eIF5A2 activation and preventing the EMT.     

Parathyroid hormone-related protein ameliorates death receptor-mediated apoptosis in lung cancer cells

Parathyroid hormone-related protein (PTHrP) is expressed in more advanced, aggressive tumors and may play an active role in cancer progression. This study investigated the effects of PTHrP on apoptosis after UV irradiation, Fas ligation, or staurosporine treatment in BEN human squamous lung carcinoma cells. Cells at 70% confluency were treated for 24 h with 100 nM PTHrP-(1-34), PTHrP-(38-64), PTHrP-(67-86), PTHrP-(107-139), or PTHrP-(140-173) in media with serum, exposed for 30 min to UV-B radiation (0.9 mJ/cm²), and maintained for another 24 h. Caspase-3, caspase-8, and caspase-9 activities increased fivefold. Pretreatment with PTHrP-(1-34) and PTHrP-(140-173) ameliorated apoptosis after UV irradiation, as indicated by reduced caspase activities, increased cell protein, decreased nuclear condensation, and increased clonal survival. Other peptides had no effect on measures of apoptosis. PTHrP-(140-173) also reduced caspase activities after Fas ligation by activating antibody, but neither peptide had effects on caspase-3 or caspase-9 activity after 1 µM staurosporine. These data indicate that PTHrP-(1-34) and PTHrP-(140-173) protect against death receptor-induced apoptosis in BEN lung cancer cells but are ineffective against mitochondrial pathways. PTHrP contributes to lung cancer cell survival in culture and could promote cancer progression in vivo. The mechanism for the protective effect against apoptosis remains to be determined. caspases; cell surface receptors; growth substances     

Vincristine attenuates doxorubicin cardiotoxicity

Our aim was to test the hypothesis that the vinca alkaloid vincristine could prevent doxorubicin-induced cardiomyocyte death and to identify the mechanisms involved. Adult mouse cardiac myocytes were incubated for 24 h with doxorubicin, with and without concurrent vincristine. Trypan blue exclusion showed that 50–60% of myocytes treated with doxorubicin alone survived. Concurrent vincristine treatment increased survival to 85%. Treatment with doxorubicin + vincristine activated the prosurvival signal Akt and diminished cytochrome C release. The PI3K/Akt inhibitor LY294002 and the MEK/ERK inhibitor PD98059 augmented doxorubicin cardiotoxicity and attenuated salvage during concurrent vincristine treatment, indicating that the mechanism of vincristine cardioprotection involves activation of specific survival signals. Vincristine retarded the onset of apoptosis in association with a delay in poly(ADP) ribose polymerase activation. Vincristine also exhibited greater protection than the antioxidant MPG. These novel findings may have clinical implications for the prevention of doxorubicin cardiomyopathy.     

Protectors against doxorubicin-induced cardiotoxicity: Flavonoids

Doxorubicin is a widely used anthracycline anticancer agent. Its use may cause cardiomyopathy: in fact, the development of cumulative dose-related cardiotoxicity forms the major limitation of clinical doxorubicin use. We therefore searched for protective agents that combine iron-chelating and oxygen radical-scavenging properties. Moreover, any novel protector should not interfere with the cytostatic activity of doxorubicin. After extensive in vitro screening we found that flavonoids could serve this purpose. In particular 7-monohydroxyethylrutoside almost completely protected against the negative inotropic action of doxorubicin in the electrically paced mouse left atrium model. In vivo it gave full protection at 500 mg/kg intraperitoneally against the doxorubicin-induced ST-interval lengthening in the ECG. Moreover, this protector did not influence the antitumor effect of doxorubicin either in vitro using the human ovarian cell lines A2780 and OVCAR-3 and the human breast cancer cell line MCF-7 or in vivo in A2780 and OVCAR-3 subcutaneous xenografts in nude mice. Comparison of various iron chelators suggest that iron, in contrast to the general assumption, might not play a crucial role in the oxidative stress-induced toxicity of doxorubicin. Moreover, incubation of vascular endothelial cells with doxorubicin produced overexpression of adhesion molecules, which could be inhibited by 7-monohydroxyethylrutoside. From a study in human volunteers, we conclude that an intravenous dose of 1500 mg/m² of 7-monohydroxyethylrutoside is feasible and is safe to be investigated as protection against doxorubicin-induced cardiotoxicity.