The specific 26S proteasome inhibitor bortezomib (BZ) potently induces autophagy, endoplasmic reticulum (ER) stress and apoptosis in multiple myeloma (MM) cell lines (U266, IM-9 and RPMI8226). The macrolide antibiotics including concanamycin A, erythromycin (EM), clarithromycin (CAM) and azithromycin (AZM) all blocked autophagy flux, as assessed by intracellular accumulation of LC3B-II and p62. Combined treatment of BZ and CAM or AZM enhanced cytotoxicity in MM cell lines, although treatment with either CAM or AZM alone exhibited almost no cytotoxicity. This combination also substantially enhanced aggresome formation, intracellular ubiquitinated proteins and induced the proapoptotic transcription factor CHOP (CADD153). Expression levels of the proapoptotic genes transcriptionally regulated by CHOP (BIM, BAX, DR5 and TRB3) were all enhanced by combined treatment with BZ plus CAM, compared with treatment with each reagent alone. Like the MM cell lines, the CHOP+/+ murine embryonic fibroblast (MEF) cell line exhibited enhanced cytotoxicity and upregulation of CHOP and its transcriptional targets with a combination of BZ and one of the macrolides. In contrast, CHOP−/− MEF cells exhibited resistance against BZ and almost completely canceled enhanced cytotoxicity with a combination of BZ and a macrolide. These data suggest that ER stress-mediated CHOP induction is involved in pronounced cytotoxicity. Simultaneously targeting two major intracellular protein degradation systems such as the ubiquitin-proteasome system by BZ and the autophagy-lysosome system by a macrolide antibiotic enhances ER stress-mediated apoptosis in MM cells. This result suggests the therapeutic possibility of using a macrolide antibiotic with a proteasome inhibitor for MM therapy.
The relation between expression of cell cycle-regulator molecules and apoptosis was examined in surgical specimens and cultured human lung carcinoma cell lines. Cell-cycle regulation, a fundamental mechanism determining cell proliferation, is precisely regulated by the specific interaction of cyclins, cdks and cdk-inhibitors. 1,2 Aberrant expression of cyclins and cdks is involved in oncogenic transformation in cultured cells. 3,4 Successive clinicopathologic analyses of human malignant tumors, including carcinomas of the breast, lung, gastrointestinal tract, ovary and other sites, showed a correlation between overexpression of cell-cycle proteins and worse clinical outcome.  Indeed, in previous studies of human lung carcinomas and soft tissue sarcomas, we found that the expression and kinase activity of the cyclin A/cdk2 complex were novel predictors of proliferative activity and prognosis. 6,10,11 Thus, studies in both cultured cells and human tumors have consistently suggested that dysregulated expression of cyclin/cdk complexes is crucially involved in neoplastic transformation and the aggressive phenotypes of cancers.However, in the past decade, overexpression or abnormal expression of several positive regulators of the cell cycle has been closely associated with apoptosis. These proteins include c-myc, E2F1 and the HPV oncoproteins. 12-15 Several studies have implicated cell-cycle regulator molecules in apoptosis: e.g., upregulation of cyclin D1, cdk4 and/or cdc2 may be a critical event during apoptosis in neuronal cells. 16 -18 Furthermore, several reports have implicated other cell cycle-regulatory molecules, including cyclin E and cyclin B, as key factors in the apoptosis of cultured cells. 19,20 Although these reports suggested that overexpression of any cyclin or cdk could induce apoptosis, each has been shown to have individual potential functions. Previously, we demonstrated that (i) constitutive overexpression of cdk4 significantly promotes apoptosis in rat pheochromocytoma PC12 cells; 17 (ii) in contrast, constitutive overexpression of cdk2 or cdc2 promotes cell proliferation and abrogates the response to nerve growth factor; 4,21 and (iii) transient overexpression of cdk4 or cyclin D1 induces apoptosis in the presence of trophic support in neuronal, hematopoietic and human cancer cell lines. 22,23 These results overall suggest that cdk4/cyclin D1 kinase plays a specific and crucial role in inducing apoptosis in a wide spectrum of cell types. However, observations of these phenomena have been limited to cultured cells and precise pathobiologic or clinicopathologic analyses on apoptosis in surgical specimens of human tumors have not been documented. Several clinicopathologic analyses of apoptosis have examined its prognostic significance in human cancers but with somewhat mixed results. In lung carcinomas, several groups have reported that enhanced apoptosis is associated with shortened survival, 24,25 yet other studies have found no statistically significant correlation. 26 In cont...
Lung cancer is a leading cause of death worldwide, and the long-term survival rate of lung cancer patients is one of the lowest among cancers.1,2) Two major types of lung cancer have been identified: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). NSCLC, the most prevalent subtype, is relatively resistant to chemotherapy and radiation therapy. On the other hand, SCLC is initially highly sensitive to chemotherapy and radiation therapy, but shows resistance to treatment in the majority of patients.3) The high mortality in NSCLC is due to the difficulty of early diagnosis and its high potential for local invasion and distant metastasis. Although relatively effective chemotherapeutic agents have been developed, lung cancer still has a low cure rate. Furthermore, the adverse effects of chemotherapeutic compounds often hamper the quality of life of lung cancer patients. Therefore, the discovery of effective novel prophylactic, diagnostic, and therapeutic treatments for NSCLC is urgently needed."Apoptosis" has been used as a synonym for programmed cell death (PCD), and is a well-known form of PCD. Since the 1960s, various morphological forms of PCD have been recognized. Clarke classified cell death into 4 types, including type I PCD (apoptosis) and type II PCD (autophagy). 4)Numerous studies have demonstrated that most chemotherapy agents and certain naturally occurring compounds induce cell death by activating the apoptotic pathway. It is thought that apoptosis induction in tumor cells with either drugs or natural products is effective therapy for cancer and immune system diseases. On the other hand, autophagy is one of the major regulatory mechanisms in the degradation of intracellular proteins and organelles. 5,6) During autophagy, the cytosol and whole organelles become encased in double-membrane vacuoles such as autophagosomes, and subsequently fuse with lysosomes.5) Degradation of the sequestered material generates nucleotides, amino acids, and free fatty acids that are recycled for macromolecular synthesis and ATP generation.7) Although originally characterized as a survival response to nutrient deficiency, autophagy is now recognized as frequently induced in response to a variety of stressors to maintain cellular homeostasis.  In recent years, the importance of autophagy has been emphasized in various biological fields, including cancer. 9, Furthermore, cancer cells show less autophagy than normal cells. 16,17) These findings indicate that autophagy induction is an attractive modality of anticancer therapy.b-Carboline alkaloids occur in a number of medicinal plants such as Peganum harmala, Passiflora edulis, Passiflora incarnata, and Banisteriopsis caapi.18,19) These plants have been used in traditional medicine to treat asthma, jaundice, lumbago, and other human ailments.19-21) Recently, it has been reported that certain b-carboline alkaloids and their related compounds have cytotoxic effects on cancer cells.  We also reported previously that harm...
The aim of this study was to investigate the anticancer effects of the phenoxazine derivatives, 2-amino-4,4·-dihydro-4·,7-dimethyl-3H-phenoxazine-3-one (Phx-1), 3-amino-1,4·-dihydro-4·,8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-aminophenoxazine-3-one (Phx-3) on human pancreatic cancer cell lines, KLM-1 and MIA-PaCa-2, in combination with tumor necrosis factor-related apoptosisinducing ligand (TRAIL), a member of the tumor necrosis factor superfamily of cytokines. Of these three phenoxazines, Phx-1 and Phx-3 inhibited proliferation of KLM-1 dosedependently, but Phx-2 did not. Phx-3 caused both apoptosis and necrosis in KLM-1 cells, as evidenced by the phosphatidylserine externalization and propidium iodide permeable cells detected by a flow cytometric method using annexin-V and propidium iodide. Down-regulation of Bcl-2 expression appeared to be involved in the Phx-3-induced cell death. TRAIL did not affect proliferation of KLM-1, and the inhibitory effects of Phx-1 and Phx-3 on the KLM-1 cell line were not augmented by the combination with TRAIL. On the other hand, proliferation of the MIA-PaCa-2 cell line was not affected by Phx-1, Phx-2 and Phx-3, although it was significantly inhibited by TRAIL in a dose-dependent manner. Inhibitory effects of TRAIL on MIA-PaCa-2 were synergistically augmented by the addition of Phx-1 and Phx-3, but not by Phx-2. These results suggest that both Phx-1 and Phx-3 exert anticancer effects against human pancreatic cancer cells, KLM-1 and MIA-PaCa-2, through distinct action modes. Phx-1 and Phx-3 may be effective for the treatment of pancreatic cancer.
Six antitumor antibiotics of a new structure class, indoxamycins A-F (1-6), were isolated from a saline culture group of marine-derived actinomyces whose strains showed approximately 96% sequence homology of 16S rDNA with the family streptomycetaceae. The structures of these indoxamycins, which are unusual polyketides composed of six consecutive chiral centers, were assigned by combined spectral and chemical methods. In feeding experiments using a stable isotope label, indoxamycin A was assembled from propionate units initially forming the "aglycon" pentamethyl indeno furan. The discovery of these unprecedented compounds from marine-derived actinomycetes, a low gene homology genus, offers a significant opportunity for drug discovery.
Anti-tumor effects of a novel phenoxazinone, 2-amino-4,4-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx), which was synthesized by the reaction of 2-amino-5-methylphenol with bovine hemoglobin, were studied in terms of suppression of the proliferation of human lung carcinoma cells and apoptosis induction. When Phx was added to cultures of the human lung carcinoma cell lines A549 (adenocarcinoma) and H226 (squamous carcinoma), it caused the growth inhibition and the death of these cells. Phx also fragmented the DNA of these cells to oligonucleosomal-sized fragments, which is characteristic of the apoptosis, dependent on the dose and exposure time. The cellular death caused by the administration of Phx was partially reversed by the addition of Z-VAD-fmk, a caspase family inhibitor. Present results suggest that Phx demonstrates anti-cancer activity against human lung carcinoma cell lines A549 and H226, by inhibiting growth and inducing apoptosis.
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