Routine surveillance endomyocardial biopsy

Candidate early predictive plasma protein markers of doxorubicin-induced chronic cardiotoxicity in B6C3F1 mice

Cardiotoxicity is a serious adverse effect of doxorubicin (DOX) treatment in cancer patients. Currently, there is a lack of sensitive biomarkers to predict the risk of DOX-induced cardiotoxicity. Using SOMAmer-based proteomic technology, 1129 proteins were profiled to identify potential early biomarkers of cardiotoxicity in plasma from male B6C3F₁ mice given a weekly intravenous dose of 3 mg/kg DOX or saline (SAL) for 2, 3, 4, 6, or 8 weeks (6, 9, 12, 18, or 24 mg/kg cumulative DOX doses, respectively). Also, a group of mice received the cardio-protectant, dexrazoxane (DXZ; 60 mg/kg; intraperitoneal) 30 min before a weekly DOX or SAL dose. Proteomic analysis in plasma collected a week after the last dose showed a significant ≥1.2-fold change in level of 18 proteins in DOX-treated mice compared to SAL-treated counterparts during 8-week exposure. Of these, neurogenic locus notch homolog protein 1 (NOTCH1), von Willebrand factor (vWF), mitochondrial glutamate carrier 2, Wnt inhibitory factor 1, legumain, and mannan-binding lectin serine protease 1 were increased in plasma at 6 mg/kg cumulative DOX dose, prior to the release of myocardial injury marker, cardiac troponin I at 12 mg/kg and higher cumulative doses. These six proteins also remained significantly elevated following myocardial injury or pathology at 24 mg/kg. Pretreatment of mice with DXZ significantly attenuated DOX-induced elevated levels of only NOTCH1 and vWF with mitigation of cardiotoxicity. This suggests NOTCH1 and vWF as candidate early biomarkers of DOX cardiotoxicity, which may help in addressing a clinically important question of identifying cancer patients at risk for cardiotoxicity.

Early biomarkers of doxorubicin-induced heart injury in a mouse model

Cardiac troponins, which are used as myocardial injury markers, are released in plasma only after tissue damage has occurred. Therefore, there is a need for identification of biomarkers of earlier events in cardiac injury to limit the extent of damage. To accomplish this, expression profiling of 1179 unique microRNAs (miRNAs) was performed in a chronic cardiotoxicity mouse model developed in our laboratory. Male B6C3F1 mice were injected intravenously with 3mg/kg doxorubicin (DOX; an anti-cancer drug), or saline once a week for 2, 3, 4, 6, and 8weeks, resulting in cumulative DOX doses of 6, 9, 12, 18, and 24mg/kg, respectively. Mice were euthanized a week after the last dose. Cardiac injury was evidenced in mice exposed to 18mg/kg and higher cumulative DOX dose whereas examination of hearts by light microscopy revealed cardiac lesions at 24mg/kg DOX. Also, 24 miRNAs were differentially expressed in mouse hearts, with the expression of 1, 1, 2, 8, and 21 miRNAs altered at 6, 9, 12, 18, and 24mg/kg DOX, respectively. A pro-apoptotic miR-34a was the only miRNA that was up-regulated at all cumulative DOX doses and showed a significant dose-related response. Up-regulation of miR-34a at 6mg/kg DOX may suggest apoptosis as an early molecular change in the hearts of DOX-treated mice. At 12mg/kg DOX, up-regulation of miR-34a was associated with down-regulation of hypertrophy-related miR-150; changes observed before cardiac injury. These findings may lead to the development of biomarkers of earlier events in DOX-induced cardiotoxicity that occur before the release of cardiac troponins.

Noninvasive monitoring of rejection therapy based on intramyocardial electrograms after orthotopic heart transplantation. Initial experience with 14 cases

Despite the use of increasingly specific immunosuppressive therapy, rejection remains the leading cause of death in cardiac transplant patients. Endomyocardial biopsy (EMB) is the gold standard for early detection and monitoring of cardiac transplant rejection. However, this approach is invasive and not suitable for routine use. A noninvasive alternative for monitoring cardiac transplant patients uses the analysis of the ventricular evoked response (VER) obtained by programmed electrical stimulation. Rejection-sensitive parameters (RSP) and infection-specific parameters (ISP) are extracted from changes in the slope of the T-wave and from the duration of repolarization, respectively. For the analysis of intramyocardial electrograms, separate left and right ventricular pacing at a rate of 100 beats/min and lasting 60 s is required, following the same protocol. From year 2000, telemetric pacemakers were implanted in 14 patients undergoing heart transplantation at this institution. A total of 95 endomyocardial biopsies and 275 ventricular evoked response measurements were carried out. Five out of 6 cases with significant rejection were correctly identified by RSP values below a threshold of 98% (sensitivity=80%, specificity=50%, negative predictive value=97%, positive predictive value=11%; P<0.002). Of the EMBs, 45% could have been saved if the diagnosis model had been used to indicate need for EMB. Noninvasive cardiac graft monitoring can reduce the need for surveillance biopsies and may offer a tool to optimize immunosupressive therapy after heart transplantation. Rejection grade 2 or higher can safely be detected.