Suman Sengupta

EGFR upregulates inflammatory and proliferative responses in human lung adenocarcinoma cell line (A549), induced by lower dose of cadmium chloride

Exposure to cadmium is associated with the development of pulmonary damage such as emphysema and lung cancer. This metal is also a powerful inducer of different proinflammatory and cell cycle regulatory proteins in many biologic models. Previously, we showed that prolonged exposure of low concentration of cadmium resulted in upregulation of proinflammatory cytokines and cell cycle regulatory molecules in mice lung cell. The present study was undertaken to determine molecular mechanism of inflammation and its relation to cell proliferation in a transformed human lung adenocarcinoma epithelial cell line (A549) in response to cadmium chloride. In comparative studies, we examine that short-duration exposure to lower doses of cadmium significantly increase the growth of A549 cells, whereas higher doses are toxic and cause cell death. We also observed that cadmium induced elevated expression of epidermal growth factor receptor (EGFR) along with different proinflammatory cytokines like interleukin-1 beta (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). The possible occurrence of cell proliferation events was evaluated via analysis of the physical state of the DNA and the expression of Ki-67 and proliferating cell nuclear antigen (PCNA). We also checked the pattern of expression of different cell cycle regulatory molecules involved in the onset of cell proliferation. Our results indicate that cadmium treatment appears to induce inflammatory and growth responses in transformed A549 cell line by activating EGFR and its downstream modulators. These results may contribute to better understand the toxic mechanism of cadmium; moreover, the expression profile of cadmium-induced regulatory molecules could provide potential biomarkers for cadmium exposure.

TGF-β-Smad2 dependent activation of CDC 25A plays an important role in cell proliferation through NFAT activation in metastatic breast cancer cells

In late stages of cancer, TGF-β promotes the metastasis process by enhancing the invasiveness of cancer cells and inducing the epithelial-to-mesenchymal transition (EMT), a process that is concomitantly associated with breast cancer metastasis. Metastasis comprises of multiple steps with the regulation of complex network of signaling. Metastasis is associated with both the EMT and cell proliferation, but yet it has not been clearly distinguished how the balance between the cell proliferation and EMT is maintained together. Recently, it has been accounted that a transcription factor, NFAT has an important role for switching tumor suppressive to progressive effect of TGF-β and NFAT has a role in TGF-β mediated EMT by regulating N-cadherin. CDC 25A phosphatase, an important cell cycle regulator is overexpressed in breast cancer. Our results demonstrate that TGF-β regulating the CDC 25A in a Smad2 dependent way, translocates NFAT to nucleus and NFAT in co-operation with Smad2 promotes the tumor progression by upregulating the CDK2, CDK4, and cyclin E. This result signifies that TGF-β by regulating NFAT in different ways maintains the balance between EMT and cell proliferation mechanism concurrently during the late stage of breast cancer.

Low fucose containing bacterial polysaccharide facilitate mitochondria-dependent ROS-induced apoptosis of human lung epithelial carcinoma via controlled regulation of MAPKs-mediated Nrf2/Keap1 homeostasis signaling

Reactive oxygen species (ROS), the key mediators of cellular oxidative stress and redox dysregulation involved in cancer initiation and progression, have recently emerged as promising targets for anticancer drug discovery. Continuous free radical assault upsets homeostasis in cellular redox system and regulates the associated signaling pathways to mediate stress‐induced cell death. This study investigates the dose‐specific pro‐oxidative behavior of a bacterial fucose polysaccharide, which attenuated proliferation of different cancer cells. In the fermentation process, Bacillus megaterium RB‐05 [GenBank Accession Number HM371417] was found to biosynthesize a polysaccharide with low‐fucose content (4.9%), which conferred the maximum anti‐proliferative activity (750 µg/mL) against human lung cancer epithelial cells (A549) during preliminary screening. Structural elucidation and morphological characterization of the duly purified polysaccharide was done using HPLC, GC‐MS, 1H/13C NMR, and microscopy. The polysaccharide exhibited concentration‐ and time‐dependent anti‐proliferative effects against A549 cells by inducing intracellular ROS level and regulating the mitochondrial membrane‐permeability following the apoptotic pathway. This process encompasses activation of caspase‐8/9/3/7, increase in the ratio of Bax/Bcl2 ratio, translocation of Bcl2‐associated X protein (Bax) and cytochrome c, decrease in expression of anti‐apoptotic members of Bcl2 family, and phosphorylation of mitogen activated protein kinases (MAPKs). Apoptosis was attenuated upon pretreatment with specific caspase‐inhibitors. Simultaneously, during apoptosis, the ROS‐mediated stress as well as activated MAPKs triggered nuclear translocation of transcription factors like nuclear factor (erythroid‐derived)‐like 2 (Nrf2) and promoted further transcription of downstream cytoprotective genes, which somehow perturbed the chemotherapeutic efficacy of the polysaccharide, although using CuPP, a chemical inhibitor of HO‐1, apoptosis increased significantly (P < 0.05).

A pharmaceutical cocrystal with potential anticancer activity

The design of pharmaceutical cocrystals has become a prime thrust of crystal engineering and the pharmaceutical industry in recent times – but the use of pharmaceutical cocrystals as regular drugs is yet to be explored. Quinoxaline acts as a basic skeleton of several potential anticancer drugs. We have successfully cocrystallized quinoxaline with another organic molecule 3-thiosemicarbano-butan-2-one-oxime (TSBO, a virus replication inhibitor) and examined the anticancer activity of the cocrystal. The crystal structure of the cocrystal was determined by single crystal X-diffraction study. According to thermogravimetric study the cocrystal exhibits better thermal stability than quinoxaline. UV-Vis spectroscopic study has shown that in solution state the behavior of the cocrystal and the physical mixture of its components (mixture of quinoxaline and TSBO) are significantly different. The solubility of the cocrystal in distilled water has been found to be 31.9 mg mL−1. The cocrystal exhibits a specific cytotoxic effect on lung cancer cells (A549) at 10−7 M concentration while it shows growth inhibitory effect on normal cells. The detailed mechanistic study of the cytotoxicity of the cocrystal suggests that it follows the mitochondrial mediated cell death pathway through activation of Caspase 9 and Bax. It also shows anticancer activity on breast cancer cells (MCF-7).

Attenuation of Smad2 activity shows resistance to TGF-β signalling in mammary adenocarcinoma (MCF-7) cells.

Transforming growth factor‐β (TGF‐β) is a potent inhibitor of the growth of normal mammary epithelial cells, and has a pleiotropic, context‐dependent, concentration‐dependent action. We found attenuation of TGF‐β signalling in mammary adenoma carcinoma cells. Phosphorylation at the linker site of Smad2 occurred in a cooperative way during the attenuation of TGF‐β signalling, and was associated with upregulation of CDK2 and cyclin D1. CDK2 inhibitor restored the anti‐proliferative effect of TGF‐β by upregulating p21, with inhibition of linker phosphorylation of Smad2. CDK2‐mediated linker phosphorylation of Smad2 may be a plausible mechanism for the attenuation of TGF‐β signalling in breast cancer.