Cardiotoxicity of the anticancer therapeutic agent bortezomib.

Recent case reports provided alarming signals that treatment with bortezomib might be associated with cardiac events. In all reported cases, patients experiencing cardiac problems were previously or concomitantly treated with other chemotherapeutics including cardiotoxic anthracyclines. Therefore, it is difficult to distinguish which components of the therapeutic regimens contribute to cardiotoxicity. Here, we addressed the influence of bortezomib on cardiac function in rats that were not treated with other drugs. Rats were treated with bortezomib at a dose of 0.2 mg/kg thrice weekly. Echocardiography, histopathology, and electron microscopy were used to evaluate cardiac function and structural changes. Respiration of the rat heart mitochondria was measured polarographically. Cell culture experiments were used to determine the influence of bortezomib on cardiomyocyte survival, contractility, Ca(2+) fluxes, induction of endoplasmic reticulum stress, and autophagy. Our findings indicate that bortezomib treatment leads to left ventricular contractile dysfunction manifested by a significant drop in left ventricle ejection fraction. Dramatic ultrastructural abnormalities of cardiomyocytes, especially within mitochondria, were accompanied by decreased ATP synthesis and decreased cardiomyocyte contractility. Monitoring of cardiac function in bortezomib-treated patients should be implemented to evaluate how frequently cardiotoxicity develops especially in patients with pre-existing cardiac conditions, as well as when using additional cardiotoxic drugs.

Zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, demonstrates potent antitumor effects but is unable to potentiate antitumor effects of chemotherapeutics in mice.

BACKGROUND: HO-1 participates in the degradation of heme. Its products can exert unique cytoprotective effects. Numerous tumors express high levels of HO-1 indicating that this enzyme might be a potential therapeutic target. In this study we decided to evaluate potential cytostatic/cytotoxic effects of zinc protoporphyrin IX (Zn(II)PPIX), a selective HO-1 inhibitor and to evaluate its antitumor activity in combination with chemotherapeutics. METHODS: Cytostatic/cytotoxic effects of Zn(II)PPIX were evaluated with crystal violet staining and clonogenic assay. Western blotting was used for the evaluation of protein expression. Flow cytometry was used to evaluate the influence of Zn(II)PPIX on the induction of apoptosis and generation of reactive oxygen species. Knock-down of HO-1 expression was achieved with siRNA. Antitumor effects of Zn(II)PPIX alone or in combination with chemotherapeutics were measured in transplantation tumor models. RESULTS: Zn(II)PPIX induced significant accumulation of reactive oxygen species in tumor cells. This effect was partly reversed by administration of exogenous bilirubin. Moreover, Zn(II)PPIX exerted potent cytostatic/cytotoxic effects against human and murine tumor cell lines. Despite a significant time and dose-dependent decrease in cyclin D expression in Zn(II)PPIX-treated cells no accumulation of tumor cells in G1 phase of the cell cycle was observed. However, incubation of C-26 cells with Zn(II)PPIX increased the percentage of cells in sub-G1 phase of the cells cycle. Flow cytometry studies with propidium iodide and annexin V staining as well as detection of cleaved caspase 3 by Western blotting revealed that Zn(II)PPIX can induce apoptosis of tumor cells. B16F10 melanoma cells overexpressing HO-1 and transplanted into syngeneic mice were resistant to either Zn(II)PPIX or antitumor effects of cisplatin. Zn(II)PPIX was unable to potentiate antitumor effects of 5-fluorouracil, cisplatin or doxorubicin in three different tumor models, but significantly potentiated toxicity of 5-FU and cisplatin. CONCLUSION: Inhibition of HO-1 exerts antitumor effects but should not be used to potentiate antitumor effects of cancer chemotherapeutics unless procedures of selective tumor targeting of HO-1 inhibitors are developed.

The relationship between admission heart rate and early prognosis in patients with ST-elevation myocardial infarction.

BACKGROUND: Heart rate (HR) is a basic cardiovascular parameter. The relationship between HR and cardiovascular mortality and morbidity has been indicated in clinical trials and epidemiological studies. AIM: The evaluation of the relationship between HR upon hospital admission and the in-hospital prognosis in a group of patients with ST-elevation myocardial infarction (STEMI). METHODS: The medical records of 927 patients were subject to retrospective analysis. The patients were classified on the basis of HR upon hospital admission: < 60 bpm (n = 75), 60-69 bpm (n = 169), 70-79 bpm (n = 245), 80-89 bpm (n = 172), 90-99 bpm (n = 134), and ≥ 100 bpm (n = 132). A group of patients with HR of 60-69 bpm on hospital admission (n = 169) constituted a reference group. Patients with atrioventricular blocks and arrhythmias were excluded from the analysis. Early mortality and co-existing diseases were evaluated in the study population. RESULTS: Patients with HR ≥ 90 bpm demonstrated heart failure symptoms considerably more often than patients with HR of 60-69 bpm (p = 0.0010). In-hospital mortality was significantly higher in patients with a HR of more than 90 bpm and bradycardia. The relationship between HR and cardiovascular mortality is shown with a J-shaped curve. CONCLUSIONS: HR is strictly correlated with early cardiovascular mortality in a population of patients with STEMI. The relationship between HR and early mortality is demonstrated by a J-shaped curve.

Variability of circadian blood pressure profile during 24-hour ambulatory blood pressure monitoring in hypertensive patients.

BACKGROUND: Evaluation of circadian blood pressure (BP) profile is an important element of ambulatory BP monitoring (ABPM). Abnormal nocturnal fall in BP is more common in patients with secondary causes of hypertension and in the elderly. Cardiovascular risk is substantially increased in these patients. AIM: Analysis of circadian BP profile in a population of treated hypertensives and identification of factors affecting variability of nocturnal fall in BP. METHODS: 24-h ABPM was performed in hypertensive patients. Based on nocturnal fall pattern, four subgroups were identified:dippers, non-dippers, extreme dippers, and risers. Comorbidities were assessed, and data obtained in all groups were compared with the dipper profile group. RESULTS: We analysed 161 patients (86 men, 53.4%). A dipper profile was noted in 44.7% of patients. Abnormal circadian BP profile was observed in 55.3% of patients, including a non-dipper profile in 21.1% of patients, an extreme dipper profilein 32.3% of patients, and a riser profile in 1.9% of patients. No significant differences in the rates of dyslipidaemia, previous myocardial infarction, previous stroke, and coronary artery disease were seen between the groups. The whole study population was also characterised by similar rates of excessive body weight and abdominal obesity. CONCLUSIONS: An abnormal circadian BP profile was found in over 50% of hypertensive patients. A negative correlation was found between nocturnal BP fall and the patient age. No differences were found between groups with different circadian BP pattern regarding duration of hypertension and the presence of dyslipidaemia, obesity, diabetes, or coronary artery disease.

Blood pressure load in adults with treated hypertension.

BACKGROUND AND AIM: To assess blood pressure (BP) load in a population of treated hypertensive patients. METHODS: The study group consisted of 137 hypertensive adults, including 75 (54.75%) men and 62 (45.25%) women, with either formerly or newly diagnosed hypertension based on office BP measurements. The median age in the whole study group was 52 years (47 and 56 years among men and women, respectively). The mean body mass index (BMI) was 27 ± 4 kg/m², and median duration of hypertension was 3 years. We divided the study group into subgroups depending on age, gender, BMI, and duration of hypertension. All patients underwent single 24-h ambulatory BP monitoring. We calculated 24-h, daytime and nighttime BP loads separately for systolic and diastolic BP. Statistical analysis was carried out using the SPSS 15.0 environment. RESULTS: Men were significantly younger than women (48.17 vs. 55.48 years, p < 0.02). Mean BMI was higher in men than women (28 vs. 26 kg/m², p < 0.044). There were no differences in the mean values of BP load depending on gender, BMI and, duration of hypertension (p = NS). Twenty-four hour and daytime diastolic BP load was higher in patients aged 41-65 years than in patients above 65 years (32.4 vs. 20.8%, p < 0.04; and 29.6 vs. 17.5%, p < 0.03). A negative correlation was found between daytime diastolic BP load and age (r = -0.19, p < 0.026) and a positive correlation was found between night time systolic BP load and age (r = 0.24, p < 0.005). CONCLUSIONS: There was no relationship between BP load and gender, BMI, and duration of hypertension. Diastolic BP load was age-related. Middle-aged patients were characterised by significantly higher values of 24-h and daytime diastolic BP load than the elderly patients.

Approaches to improve photodynamic therapy of cancer.

Photodynamic therapy (PDT) is a clinically approved method of tumor treatment. Its unique mechanism of action results from minimal invasiveness and high selectivity towards transformed cells. However, visible light used to excite most photosensitizers has rather limited ability to penetrate tissues resulting in insufficient destruction of deeply seated malignant cells. Therefore, novel strategies for further potentiation of the anticancer effectiveness of PDT have been developed. These include combined treatments with surgery, chemo- and radiotherapy, strategies targeting cytoprotective mechanisms induced in PDT-treated cells, as well as attempts aimed at enhancement of PDT-mediated antitumor immune response. Moreover, new photosensitizers and novel light sources are being developed. Impressive progress in nanotechnology and understanding of tumor cell biology rise hopes for further improvements in this elegant and promising method of cancer treatment.

Proteasome inhibition potentiates antitumor effects of photodynamic therapy in mice through induction of endoplasmic reticulum stress and unfolded protein response.

Photodynamic therapy (PDT) is an approved therapeutic procedure that exerts cytotoxic activity toward tumor cells by inducing production of reactive oxygen species such as singlet oxygen. PDT leads to oxidative damage of cellular macromolecules, including proteins that undergo multiple modifications such as fragmentation, cross-linking, and carbonylation that result in protein unfolding and aggregation. Because the major mechanism for elimination of carbonylated proteins is their degradation by proteasomes, we hypothesized that a combination of PDT with proteasome inhibitors might lead to accumulation of carbonylated proteins in endoplasmic reticulum (ER), aggravated ER stress, and potentiated cytotoxicity toward tumor cells. We observed that Photofrin-mediated PDT leads to robust carbonylation of cellular proteins and induction of unfolded protein response. Pretreatment of tumor cells with three different proteasome inhibitors, including bortezomib, MG132, and PSI, gave increased accumulation of carbonylated and ubiquitinated proteins in PDT-treated cells. Proteasome inhibitors effectively sensitized tumor cells of murine (EMT6 and C-26) as well as human (HeLa) origin to PDT-mediated cytotoxicity. Significant retardation of tumor growth with 60% to 100% complete responses was observed in vivo in two different murine tumor models (EMT6 and C-26) when PDT was combined with either bortezomib or PSI. Altogether, these observations indicate that combination of PDT with proteasome inhibitors leads to potentiated antitumor effects. The results of these studies are of immediate clinical application because bortezomib is a clinically approved drug that undergoes extensive clinical evaluations for the treatment of solid tumors.