Bikas Chandra Pal

Apoptotic effects of mahanine on human leukemic cells are mediated through crosstalk between Apo-1/Fas signaling and the Bid protein and via mitochondrial pathways

Apo-1 (Fas/CD95), a cell surface receptor, triggers apoptosis after binding to its physiological ligand, Apo-1L (FasL/CD95L). This study reports that mahanine, purified from the leaves of Murraya koenigii, has a dose- and time-dependent anti-proliferative activity in acute lymphoid (MOLT-3) and chronic myeloid (K562) leukemic cell lines and in the primary cells of leukemic and myeloid patients, with minimal effect on normal immune cells including CD34(+) cells. Leukemic cells underwent phosphatidylserine externalization and DNA fragmentation, indicating mahanine-induced apoptosis. An increase in reactive oxygen species suggests that the mahanine-induced apoptosis was mediated by oxidative stress. A significant drop in the Bcl2/Bax ratio, the loss of mitochondrial transmembrane potential as well as cytochrome c release from the mitochondria to the cytosol suggested involvement of the mitochondrial pathway of apoptosis. Cytochrome c release was followed by the activation of caspase-9, caspase-3 and caspase-7, and cleavage of PARP in both MOLT-3 and K562 cells. In MOLT-3 cells, formation of the Fas-FasL-FADD-caspase-8 heterotetramer occurred, leading to the cleavage of Bid to its truncated form, which consequently resulted in formation of the mitochondrial transmembrane pore. The incubation of MOLT-3 cells with mahanine in the presence of caspase-8 inhibitor or FasL-neutralizing NOK-2 antibody resulted in the decrease of mahanine-induced cell death. Mahanine was also a potent inhibitor of K562 xenograft growth, which was evident in an athymic nude mice model. In summary, these results provide evidence for involvement of the death receptor-mediated extrinsic pathway of apoptosis in the mahanine-induced anticancer activity in MOLT-3 cells, but not in K562 cells, which are deficient in Fas/FasL.

Oxidative inhibition of Hsp90 disrupts the super-chaperone complex and attenuates pancreatic adenocarcinoma in vitro and in vivo.

Pancreatic cancer is almost always fatal, in part because of its delayed diagnosis, poor prognosis, rapid progression and chemoresistance. Oncogenic proteins are stabilized by the Hsp90, making it a potential therapeutic target. We investigated the oxidative stress‐mediated dysfunction of Hsp90 and the hindrance of its chaperonic activity by a carbazole alkaloid, mahanine, as a strategic therapeutic in pancreatic cancer. Mahanine exhibited antiproliferative activity against several pancreatic cancer cell lines through apoptosis. It induced early accumulation of reactive oxygen species (ROS) leading to thiol oxidation, aggregation and dysfunction of Hsp90 in MIAPaCa‐2. N‐acetyl‐L‐cysteine prevented mahanine‐induced ROS accumulation, aggregation of Hsp90, degradation of client proteins and cell death. Mahanine disrupted Hsp90‐Cdc37 complex in MIAPaCa‐2 as a consequence of ROS generation. Client proteins were restored by MG132, suggesting a possible role of ubiquitinylated protein degradation pathway. Surface plasmon resonance study demonstrated that the rate of interaction of mahanine with recombinant Hsp90 is in the range of seconds. Molecular dynamics simulation showed its weak interactions with Hsp90. However, no disruption of the Hsp90‐Cdc37 complex was observed at an early time point, thus ruling out that mahanine directly disrupts the complex. It did not impede the ATP binding pocket of Hsp90. Mahanine also reduced in vitro migration and tube formation in cancer cells. Further, it inhibited orthotopic pancreatic tumor growth in nude mice. Taken together, these results provide evidence for mahanine‐induced ROS‐mediated destabilization of Hsp90 chaperone activity resulting in Hsp90‐Cdc37 disruption leading to apoptosis, suggesting its potential as a specific target in pancreatic cancer.

Improved chemosensitivity in cervical cancer to cisplatin: Synergistic activity of mahanine through STAT3 inhibition

Toxicity reduction of cisplatin is necessary for improved treatment of cancer. Here we have demonstrated the synergistic growth-inhibitory effect of cisplatin on cervical cancer cells in-combination with a nontoxic herbal carbazole alkaloid, mahanine. Mahanine enhanced cisplatin-induced apoptosis and reduced its effective concentration ∼5-8 folds. Mahanine inhibited JAK1 and Src and subsequently promoted proteasome-mediated degradation of STAT3. This event was further enhanced in-combination with cisplatin and subsequently inhibited cancer cell migration. Collectively, our results revealed that mahanine may be a prospective agent to reduce the concentration of cisplatin in adjunct for the treatment of cancer and thereby decreasing its toxicity.

Hydroxychavicol, a Piper betle leaf component, induces apoptosis of CML cells through mitochondrial reactive oxygen species-dependent JNK and endothelial nitric oxide synthase activation and overrides imatinib resistance.

Alcoholic extract of Piperbetle (Piper betle L.) leaves was recently found to induce apoptosis of CML cells expressing wild type and mutated Bcr‐Abl with imatinib resistance phenotype. Hydroxychavicol (HCH), a constituent of the alcoholic extract of Piper betle leaves, was evaluated for anti‐CML activity. Here, we report that HCH and its analogues induce killing of primary cells in CML patients and leukemic cell lines expressing wild type and mutated Bcr‐Abl, including the T315I mutation, with minimal toxicity to normal human peripheral blood mononuclear cells. HCH causes early but transient increase of mitochondria‐derived reactive oxygen species. Reactive oxygen species‐dependent persistent activation of JNK leads to an increase in endothelial nitric oxide synthase‐mediated nitric oxide generation. This causes loss of mitochondrial membrane potential, release of cytochrome c from mitochondria, cleavage of caspase 9, 3 and poly‐adenosine diphosphate‐ribose polymerase leading to apoptosis. One HCH analogue was also effective in vivo in SCID mice against grafts expressing the T315I mutation, although to a lesser extent than grafts expressing wild type Bcr‐Abl, without showing significant bodyweight loss. Our data describe the role of JNK‐dependent endothelial nitric oxide synthase‐mediated nitric oxide for anti‐CML activity of HCH and this molecule merits further testing in pre‐clinical and clinical settings. (Cancer Sci 2012; 103: 88–99)

Mahanine synergistically enhances cytotoxicity of 5-fluorouracil through ROS-mediated activation of PTEN and p53/p73 in colon carcinoma

Abstract5-Fluorouracil (5-FU) alone or in combination with other drugs is the main basis of chemotherapeutic treatment in colorectal cancer although patients with microsatellite instability generally show resistance to 5-FU treatment. The present investigation is focussed on the mechanistic insight of a pure herbal carbazole alkaloid, mahanine, as a single or in combination with 5-FU in colon cancer. We demonstrated that mahanine-induced apoptosis involved reactive oxygen species (ROS)-mediated nuclear accumulation of PTEN and its interaction with p53/p73. Mahanine and 5-FU in combination exerted synergistic inhibitory effect on cell viability. This combination also enhanced ROS production, increased tumour suppressor proteins and suppressed chemo-migration. Taken together, our results revealed that mahanine can be a potential chemotherapeutic agent with efficacy to reduce the concentration of toxic 5-FU in colon cancer.

Corchorusin-D, a saikosaponin-like compound isolated from Corchorus acutangulus Lam., targets mitochondrial apoptotic pathways in leukemic cell lines (HL-60 and U937)

PurposeThe presence of triterpene saponins in Corchorus acutangulus Lam. has been reported. However, no studies concerning biological activity of the plant extracts have been done so far. In the present study, the anti-leukemic activity of the methanol extract of aerial parts (ME) of C. acutangulus has been investigated, and efforts have been made to identify the active ingredient responsible for this activity.MethodsThe anti-leukemic activity of ME, its fractions and corchorusin-D (COR-D), the active ingredient, was investigated in leukemic cell lines U937 and HL-60 using cell viability and MTT assays. The molecular pathways leading to the activity of COR-D were examined by confocal microscopy, flow-cytometry, caspase and Western blot assays.ResultsME, its n-butanolic fraction and COR-D inhibited cell growth and produced significant cytotoxicity in leukemic cell lines U937 and HL-60. COR-D produced apoptotic cell death via mitochondrial disfunction and was found to pursue the intrinsic pathway by inciting the release of apoptosis-inducing factors (AIFs) from mitochondria. COR-D-induced translocation of Bax from cytosol to mitochondria facilitating caspase-9 activation and up regulation of downstream pathways leading to caspase-3 activation and PARP cleavage, which resulted in the subsequent accumulation of cells in the sub-G0 phase followed by DNA fragmentation.ConclusionsCOR-D possesses significant anti-leukemic activity in U937 and HL-60 cell lines by acting on the mitochondrial apoptotic pathways. Since the necrotic body formation is low after COR-D treatment, the occurrence of inflammation in in vivo systems could be reduced, which represents a positive indication in view of therapeutic application.

Identification and quantification of the active component quercetin 3-O-rutinoside from Barringtonia racemosa, targets mitochondrial apoptotic pathway in acute lymphoblastic leukemia

Barringtonia racemosa has been used as a traditional medicine for the treatment of various diseases. The antitumor property of the seed extract of this plant in mice model promotes us to search for the active component present in the fruit extract. Quercetin 3-O-rutinoside (QOR) has been isolated from the fruits of this plant for the first time and quantified by HPLC method. The compound was identified by IR, mass, and NMR (1D, 2D) spectral data analysis. QOR showed dose- and time-dependent anti-proliferative activity in several leukemic cell lines with negligible effect on normal human peripheral blood mononuclear cell (PBMC). A representative T-lineage acute lymphoblastic leukemia cell line (MOLT-3) showed phosphatidyl serine externalization and DNA fragmentation, indicating QOR-induced programed cell death. We established that QOR-induced apoptosis occurred preferentially on accumulation of cells in the sub-G0 phase and genomic DNA fragmentation through the activation of mitochondria-dependent caspase cascade for the first time in T-lineage ALL cell line.