A retrospective pooled analysis of trabectedin safety in 1,132 patients with solid tumors treated in phase II clinical trials.

PURPOSE: To summarize the safety experience obtained from phase II clinical trials conducted with trabectedin as single-agent therapy in patients with advanced solid tumors. METHODS: This retrospective analysis includes 1,132 patients exposed to trabectedin in 19 phase II trials carried out between February 1999 and April 2008. Trabectedin was administered intravenously as 1 of 3 schedules: 24-hour infusion every 3 weeks (q3wk 24-h; n = 570/2,818 cycles), 3-hour infusion every 3 weeks (q3wk 3-h; n = 258/1,003 cycles), and 3-hour infusion for three consecutive weeks every 4 weeks (qwk 3-h; n = 304/1,198 cycles). RESULTS: The majority of patients (90%) had received previous chemotherapy. Patients were given a median of three treatment cycles of trabectedin (range, 1-59). Nausea, fatigue and vomiting were the most common trabectedin-related adverse events, reported in ≥20% of patients. Reversible myelosuppression (mainly neutropenia) and transient reversible transaminase increases were the most common laboratory abnormalities seen with trabectedin, with a very low incidence of relevant clinical consequences. Deaths associated with drug-related adverse events were infrequent, occurring in 19 (1.7%) patients. CONCLUSION: Single-agent trabectedin treatment was reasonably well tolerated. Trabectedin can be administered for prolonged periods to patients with sustained clinical benefit (induction of disease stability or shrinkage) without cumulative toxicities over time.

Novel role for EKLF in megakaryocyte lineage commitment.

Megakaryocytes and erythroid cells are thought to derive from a common progenitor during hematopoietic differentiation. Although a number of transcriptional regulators are important for this process, they do not explain the bipotential result. We now show by gain- and loss-of-function studies that erythroid Krüppel-like factor (EKLF), a transcription factor whose role in erythroid gene regulation is well established, plays an unexpected directive role in the megakaryocyte lineage. EKLF inhibits the formation of megakaryocytes while at the same time stimulating erythroid differentiation. Quantitative examination of expression during hematopoiesis shows that, unlike genes whose presence is required for establishment of both lineages, EKLF is uniquely down-regulated in megakaryocytes after formation of the megakaryocyte-erythroid progenitor. Expression profiling and molecular analyses support these observations and suggest that megakaryocytic inhibition is achieved, at least in part, by EKLF repression of Fli-1 message levels.

Suv39h histone methyltransferases interact with Smads and cooperate in BMP-induced repression.

Smad proteins transduce signals from transforming growth factor-beta (TGF-beta) superfamily ligands to regulate the expression of target genes. In order to identify novel partners of Smad proteins in transcriptional regulation, we performed a two-hybrid screen using Smad5, a protein that is activated predominantly by bone morphogenetic protein (BMP) signaling. We identified an interaction between Smad5 and suppressor of variegation 3-9 homolog 2 (Suv39h2), a chromatin modifier enzyme. Suv39h proteins are histone methyltransferases that methylate histone H3 on lysine 9, resulting in transcriptional repression or silencing of target genes. Biochemical studies in mammalian cells demonstrated that Smad5 binds to both known mammalian isoforms of Suv39h proteins, and that Smad proteins activated by the TGF-beta signaling pathway, Smad2 and Smad3, do not bind with significant affinity. Functional studies using the muscle creatine kinase (MCK) promoter, which is suppressed by BMP signaling, demonstrate that Suv39h proteins and Smads cooperate to repress promoter activity. These data suggest a model where association of Smad proteins with Suv39h methyltransferases can repress or silence genes involved in developmental processes, and argues that inefficient gene repression may result in the alteration of the differentiated phenotype. Thus, examination of the Smad-Suv interaction may provide insight into the mechanism of phenotypic determination mediated by BMP signaling.