Citations

Abstract Kaposi's sarcoma (KS) is the most common neoplasm in untreated AIDS patients and accounts for significant morbidity and mortality worldwide. We have recently reported that Notch signaling (which plays an important role in cell proliferation, apoptosis, and oncogenesis) is constitutively activated in KS tumor cells. Blockade of this activity using γ-secretase inhibitors resulted in apoptosis of SLK cells, a KS tumor cell line; however, this apoptosis was preceded by a prolonged G2-M cell cycle arrest. This result led us to hypothesize that the cells were undergoing mitotic catastrophe, an abnormal mitosis that leads to eventual cell death. Here, we show that Notch inhibition in KS tumor cells using γ-secretase inhibitors or Notch-1 small interfering RNA resulted in G2-M cell cycle arrest and mitotic catastrophe characterized by the presence of micronucleated cells and an increased mitotic index. Interestingly, Notch inhibition led to a sustained increase in nuclear cyclin B1, a novel observation suggesting that Notch signaling can modulate expression of this critical cell cycle protein. Further analysis showed the induction of cyclin B1 was due, at least in part, to increased nuclear factor-κB (NF-κB) activity, which was also required for the G2-M growth arrest after Notch inhibition. Taken together, these studies suggest that Notch inhibition can initiate aberrant mitosis by inducing NF-κB activity that inappropriately increases cyclin B1 resulting in cell death via mitotic catastrophe. [Mol Cancer Ther 2007;6(7):1983–92]

Quantitation of circulating tumor cells (CTCs) constitutes an emerging tool for the diagnosis and staging of cancer, assessment of response to therapy, and evaluation of residual disease after surgery. Unfortunately, no existing technology has the sensitivity to measure the low numbers of tumor cells (<1 CTC per ml of whole blood) that characterize minimal levels of disease. We present a method, intravital flow cytometry, that noninvasively counts rare CTCs in vivo as they flow through the peripheral vasculature. The method involves i.v. injection of a tumor-specific fluorescent ligand followed by multiphoton fluorescence imaging of superficial blood vessels to quantitate the flowing CTCs. Studies in mice with metastatic tumors demonstrate that CTCs can be quantitated weeks before metastatic disease is detected by other means. Analysis of whole blood samples from cancer patients further establishes that human CTCs can be selectively labeled and quantitated when present at ≈2 CTCs per ml, opening opportunities for earlier assessment of metastatic disease.

Purpose Gemcitabine as a single agent and the combination of gemcitabine and docetaxel have activity in patients with metastatic soft tissue sarcoma. To determine if the addition of docetaxel to gemcitabine improved clinical outcome of patients with metastatic soft tissue sarcomas, we compared a fixed dose rate infusion of gemcitabine versus a lower dose of gemcitabine with docetaxel. Patients and Methods In this open-label phase II clinical trial, the primary end point was tumor response, defined as complete or partial response or stable disease lasting at least 24 weeks. A Bayesian adaptive randomization procedure was used to produce an imbalance in the randomization in favor of the superior treatment, accounting for treatment-subgroup interactions. Results One hundred nineteen of 122 randomly assigned patients had assessable outcomes. The adaptive randomization assigned 73 patients (60%) to gemcitabine-docetaxel and 49 patients (40%) to gemcitabine alone, indicating gemcitabine-docetaxel was superior. The objective Response Evaluation Criteria in Solid Tumors response rates were 16% (gemcitabine-docetaxel) and 8% (gemcitabine). Given the data, the posterior probabilities that gemcitabine-docetaxel was superior for progression-free and overall survival were 0.98 and 0.97, respectively. Median progression-free survival was 6.2 months for gemcitabine-docetaxel and 3.0 months for gemcitabine alone; median overall survival was 17.9 months for gemcitabine-docetaxel and 11.5 months for gemcitabine. The posterior probability that patients receiving gemcitabine-docetaxel had a shorter time to discontinuation for toxicity compared with gemcitabine alone was .999. Conclusion Gemcitabine-docetaxel yielded superior progression-free and overall survival to gemcitabine alone, but with increased toxicity. Adaptive randomization is an effective method to reduce the number of patients receiving inferior therapy.

The action of lipoprotein lipase on triglyceride-rich lipoproteins generates fatty acids that are either transported into tissues or mix with circulating free fatty acids (FFAs) via a process known as spillover. In the present study, arterial, portal vein, and hepatic vein sampling catheters were surgically placed in nine mongrel dogs. The animals were subsequently studied after a 42-h fast during infusion of [14C]oleate and a lipid emulsion containing [3H]triolein; the emulsion was used as a surrogate for the study of chylomicron metabolism. More than one-half of splanchnic [3H]triglyceride uptake occurred in the liver, and substantial fractional spillover of [3H]oleate was observed in both liver and nonhepatic tissues (∼50% each). There was a significant correlation between FFA release from nonhepatic tissues (presumably visceral fat) and nonhepatic fractional spillover (R = 0.81, P &lt; 0.01), consistent with a model in which the rate of intracellular lipolysis influences spillover by determining the direction of net fatty acid flow between the cell and the interstitium. There was a significant correlation between “true” and “net” splanchnic spillover (R = 0.84, P &lt; 0.005), the latter representing calculation of spillover between arterial and hepatic venous blood without portal venous data. Metabolism of chylomicron triglycerides in visceral fat may be an important source of portal venous FFAs.

OBJECTIVE—Type 1 and type 2 diabetes are characterized by an ∼98 and ∼65% loss of pancreatic β-cells, respectively. Efforts to reverse either form of diabetes increasingly focus on the possibility of promoting β-cell replacement and/or regeneration. Islet transplantation has been explored, but it does not provide long-term insulin independence. One possible source of β-cell regeneration is hematopoietic stem cells. In mice, there are conflicting data as to whether hematopoietic stem cells contribute to pancreatic β-cells. We sought to establish whether hematopoietic stem cells (derived from adult donors) transdifferentiate into pancreatic β-cells in adult humans. RESEARCH DESIGN AND METHODS—We addressed this in 31 human pancreata obtained at autopsy from hematopoietic stem cell transplant recipients who had received their transplant from a donor of the opposite sex. RESULTS—Whereas some donor-derived cells were observed in the nonendocrine pancreata, no pancreatic β-cells were identified that were derived from donor hematopoietic stem cells, including two cases with type 2 diabetes. CONCLUSIONS—We conclude that hematopoietic stem cells derived from adult donors contribute minimally to pancreatic β-cells in nondiabetic adult humans. These data do not rule out the possibility that hematopoietic stem cells contribute to pancreatic β-cells in childhood or in individuals with type 1 diabetes.

AbstractSphingolipids (SLs), including glycosphingolipids, are found on the plasma membrane where they play important roles in a wide variety of cell functions, including cell‐cell communication, cell growth and differentiation, host‐pathogen interactions, and cell‐signaling events. This unit illustrates the use of fluorescent SL analogs to identify the mechanisms underlying SL endocytosis and subsequent intracellular trafficking. Techniques used to study SL domain formation at the plasma membrane, endocytic mechanisms and intracellular transport steps are highlighted. The use of biochemical treatments and dominant‐negative protein expression to block specific steps in lipid trafficking are also discussed.