Rac-WAVE2 signaling is involved in the invasive and metastatic phenotypes of murine melanoma cells

WAVEs (WASP-family verprolin-homologous proteins) regulate the actin cytoskeleton through activation of Arp2/3 complex. As cell motility is regulated by actin cytoskeleton rearrangement and is required for tumor invasion and metastasis, blocking actin polymerization may be an effective strategy to prevent tumor dissemination. We show that WAVEs, especially WAVE2, are essential for invasion and metastasis of melanoma cells. Malignant B16F10 mouse melanoma cells expressed more WAVE1 and WAVE2 proteins and showed higher Rac activity than B16 parental cells, which are neither invasive nor metastatic. The effect of WAVE2 silencing by RNA interference (RNAi) on the highly invasive nature of B16F10 cells was more dramatic than that of WAVE1 RNAi. Membrane ruffling, cell motility, invasion into the extracellular matrix, and pulmonary metastasis of B16F10 cells were suppressed by WAVE2 RNAi. WAVE2 RNAi also had a profound effect on invasion induced by a constitutively active form of Rac (RacCA). In addition, ectopic expression of both RacCA and WAVE2 in B16 cells resulted in further increase in the invasiveness than that observed in B16 cells expressing only RacCA. Thus, WAVE2 acts as the primary effector downstream of Rac to achieve invasion and metastasis, suggesting that suppression of WAVE2 activity holds a promise for preventing cancer invasion and metastasis.     

Hematopoietic cytokines enhance Chk1-dependent G2/M checkpoint activation by etoposide through the Akt/GSK3 pathway to inhibit apoptosis

Hematopoietic cytokines play crucial roles in regulation of cell cycle progression and apoptosis of hematopoietic cells. However, the effects of cytokines on cellular responses to chemotherapeutic agents and the mechanisms involved have remained elusive. Here we report that erythropoietin or IL-3 promotes G2/M arrest and prevents apoptosis induced by the topoisomerase II inhibitor etoposide in murine hematopoietic 32D cells and human leukemic UT7 cells. Erythropoietin or IL-3 significantly enhanced etoposide-induced activation-specific phosphorylation of Chk1, a checkpoint kinase that inhibits Cdc2 activation by Cdc25 phosphatases, and led to the inhibition of Cdc2 kinase activity with the persistent inhibitory phosphorylation on Tyr15. The inhibitory Cdc2 phosphorylation and G2/M block by etoposide were enhanced or inhibited by overexpression of Chk1 or by the specific Chk1 inhibitor SB218078, respectively. The G2/M arrest induced by etoposide was also enhanced or inhibited by expression of a constitutively activated or dominant-negative Akt mutant, respectively. Furthermore, SB216763 or LiCl, a specific inhibitor for the GSK3 kinase inhibited by Akt, enhanced the Chk1 phosphorylation and G2/M arrest by etoposide. These results indicate that hematopoietic cytokines protect etoposide-treated cells from DNA damage-induced apoptosis by promoting, through the PI3K/Akt/GSK3 signaling pathway, G2/M checkpoint that is dependent on Chk1-mediated inhibition of Cdc2.     

Arsenic trioxide (As(2)O(3)) induces apoptosis through activation of Bax in hematopoietic cells

This study explores the roles of Bax and other Bcl-2 family members play in arsenic trioxide (As(2)O(3))-induced apoptosis. We showed that As(2)O(3) treatment triggered Bax conformational change and subsequent translocation from cytosol to mitochondria to form various multimeric homo-oligomers in IM-9 cells. On the other hand, human leukemic Jurkat cells deficient in Bax showed dramatically reduced apoptosis in response to As(2)O(3). Stable overexpression of Bcl-2 in IM-9 cells (IM-9/Bcl-2) inhibited As(2)O(3)-mediated Bax activation and apoptosis, and this inhibition could be partially averted by cell-permeable Bid-Bcl-2 homology (BH)3 peptide. Meanwhile, Bax conformational change and oligomerization induced by As(2)O(3) were not inhibited by the pancaspase inhibitor z-VAD-fmk, although Bid cleavage could be completely abolished. Bax activation by As(2)O(3) seemed to require stress-induced intracellular reactive oxygen species (ROS), since the ROS scavengers (N-acetyl-L-cysteine and lipoic acid) could completely block the conformational change and translocation of Bax from cytosol to mitochondria. These data suggest that As(2)O(3) might exert the cell killing in part by inducing Bax activation through a Bcl-2-suppressible pathway in hematopoietic cells that is caspase independent and intracellular ROS regulated.     

Methylseleninic acid sensitizes prostate cancer cells to TRAIL-mediated apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytotoxic agent that preferentially induces apoptosis in a variety of human cancer cells. Unfortunately, some tumor cells remain resistant to TRAIL. Therefore, agents that sensitize malignant cells to TRAIL-mediated cell death might be of particular importance for the development of novel antitumor therapeutic regimens. Recent studies establish a critical role of selenium in prostate cancer prevention in vitro and in vivo. Here, we demonstrate that concomitant administration of TRAIL and methylseleninic acid (MSA) produces synergistic effects on the induction of apoptosis in androgen-dependent LNCaP and androgen-independent DU-145 prostate cancer cells. MSA rapidly and specifically downregulates expression of the cellular FLICE inhibitory protein, a negative regulator of death receptor signaling. In addition, we demonstrate that the synergistic effects of MSA and TRAIL result from the activation of the mitochondrial pathway-mediated amplification loop. Addition of MSA effectively blocked TRAIL-mediated BAD phosphorylation at Ser112 and Ser136 in DU-145 cells and was accompanied by induction of the mitochondrial permeability transition and release of apoptogenic cytochrome c and Smac/DIABLO proteins from the mitochondria and into the cytosol. These results suggest that selenium-based dietary compounds may help to overcome resistance to TRAIL-mediated apoptosis in prostate cancer cells.     

Importance of thymidine phosphorylase expression in tumor stroma as a prognostic factor in patients with advanced colorectal carcinoma

Thymidine phosphorylase (TP) is a unique enzyme involved not only in angiogenesis, but in 5-fluorouracil (5-FU) metabolism as well. TP is produced by both tumor and stromal cells. The aim of this study was to reveal the clinical implication of TP localization in tumor tissues. Advanced colorectal cancer specimens (n=97) were prepared for immunohistochemical staining using monoclonal antibodies against TP, p53, vascular endothelial growth factor (VEGF), factor VIII, CD68 and thymidylate synthase (TS). Clinicopathological factors and the clinical prognosis were examined for each indicator. High tumor TP expression and high stromal TP expression were observed in 38% (36/95 cases) and 49% (47/95 cases) of the cases, respectively. High tumor TP expression tended to correlate with microvessel density (MVD) (p=0.0511). Among patients who underwent curative resection, those with high stromal TP expression had a favorable prognosis (p=0.0127). High stromal TP status was also a strong prognostic factor in the group receiving adjuvant 5-FU derivatives (p=0.0222). TP produced by tumor cells has a stimulatory effect on tumor angiogenesis, while that produced by stromal cells plays an entirely different role. The latter may enhance the anticancer effect of 5-FU via its catalyzed function.     

Small cell carcinoma of the esophagus responding to fourth-line chemotherapy with weekly paclitaxel

A patient was diagnosed with a small cell carcinoma of the esophagus (T4N1M1b by the International Union Against Cancer [UICC] classification) in October 2002, and initially received two courses of concurrent chemotherapy with 5-fluorouracil (5-FU; 400 mg/m² by continuous infusion; days 1–5 and 8–12) and cisplatin (40 mg/m² by drip infusion; days 1 and 8) and radiation therapy (2 Gy/day, days 1–5, 8–12, and 15–19; total, 30 Gy per course) with the second course given after a 2-week interval. Two courses of chemotherapy with 5-FU (800 mg/m²; days 1–5) and cisplatin (80 mg/m²; day 1) given after this was completed. Although a complete response had been confirmed, recurrence with multiple liver and lymph node metastases was detected 3 months after the cessation of the second course of chemotherapy. Although the patient received second-line chemotherapy with irinotecan (150 mg/m²; every 2 weeks) from June 2003, the disease progressed. Brain metastases developed during third-line chemotherapy with gemcitabine (1000 mg/m² weekly by drip infusion). The symptoms were attenuated after whole-brain radiation (30 Gy), and fourth-line chemotherapy using paclitaxel (80 mg/m²; weekly) was initiated from November 2003. A computed tomography scan 1 month after the first course of paclitaxel showed remarkable regression of the liver metastases. The treatment strategy used for treating small cell carcinomas of the lung may be applicable for these carcinomas of the esophagus.     

Advanced chemoresistant breast cancer responding to multidisciplinary treatment with hyperthermia, radiotherapy, and intraarterial infusion

We employed multidisciplinary therapy, consisting of hyperthermia, radiotherapy, and intraarterial infusion, for a patient with progressive advanced breast cancer that was resistant to epirubicin hydrochloride and cyclophosphamide (EC) therapy as well as being resistant to docetaxel hydrate, and obtained a good therapeutic response. Because estrogen and progesterone receptors were both negative and HER2 was 3(+), administration of trastuzumab was started, and this patient has shown no signs of recurrence at 33 months after our treatment. The results suggested that our multidisciplinary therapy can be an effective method for the treatment of progressive breast cancer showing resistance to major chemotherapy agents such as anthracyclines and taxanes.     

Nitric oxide inhibits the bradykinin B2 receptor-mediated adrenomedullary catecholamine release but has no effect on adrenal blood flow response in vivo

The role of nitric oxide (NO) in bradykinin (BK)-induced adrenal catecholamine secretion still remains obscure. The present study was to investigate whether an inhibition of NO synthase with N(omega)-nitro-L-arginine methyl ester (L-NAME) would modulate BK-induced adrenal catecholamine secretion (ACS) and adrenal vasodilating response (AVR) in anesthetized dogs. Plasma catecholamine concentrations were determined with an HPLC coupled with an electrochemical detector. All drugs were locally administered to the left adrenal gland via intra-arterial infusion. BK dose-dependently increased both ACS and AVR. Hoe-140, a selective B(2) antagonist, significantly blocked the BK-induced increases in both ACS and AVR. In the presence of L-NAME, the BK-induced ACS was significantly enhanced, while the simultaneous AVR remained unaffected. These results suggest that the both BK-induced ACS and AVR are primarily mediated by B(2) receptors in the canine adrenal gland. Our results also suggest that the enhanced ACS in response to BK in the presence of L-NAME may have resulted from a specific inhibition of NO formation in the adrenal gland. It is concluded that the BK-induced NO may play an inhibitory role in the B(2)-receptor-mediated mechanisms regulating ACS, while it may not be implicated in the B(2)-receptor-mediated AVR under in vivo conditions.     

Dopamine D<Subscript>2</Subscript> receptor plays a role in memory function: implications of dopamine–acetylcholine interaction in the ventral hippocampus

Rationale The role of the hippocampal dopaminergic system in mnemonic function has not been clarified yet. Objective We previously reported that the dopamine D₂ receptor (D₂R) is involved in the regulation of acethylcholin (ACh) release in the hippocampus. In this study, we further investigated ACh–dopamine (DA) interaction in the hippocampus and its involvement in mnemonic function. Methods For experiment 1, rats fed with Cholin (Ch)-deficient chow were used. We examined the effects of D₂R antagonist, raclopride, on cognitive performance using a passive avoidance task. We further carried out in vivo microdialysis to assess the effect of infusion of D₂R agonist, quinpirole, into the ventral hippocampus on its capacity to release ACh. For experiment 2, rats fed with normal chow were used. The performance of a radial arm maze task was assessed to examine the effects of hippocampal injection of D₂R agonist, quinpirole, on memory impairment induced by scopolamine, a muscarinic ACh antagonist. Results In experiment 1, rats fed with Ch-deficient chow showed impaired performances indicated by prolonged latency on retention trials of a passive avoidance task following the hippocampal injection of D₂R antagonist, and showed reduced capacity to release ACh following the injection of D₂R agonist compared with rats fed with normal chow. In experiment 2, memory impairment induced by the intraperitoneal injection of scopolamine was ameliorated by the injection of D₂R agonist into the ventral hippocampus. Conclusion These results indicate the possible involvement of hippocampal ACh–DA interaction in mnemonic processing.