Background: Insensitivity towards anthracycline drugs like doxorubicin poses a significant challenge in the treatment of breast cancer. Among several factors, Aurora A (a mitotic serine threonine kinase) plays crucial roles in acquiring non-responsiveness towards doxorubicin. However, the mechanisms underlying need to be elucidated. The present study was therefore designed to evaluate the underlying mechanisms of Aurora A mediated doxorubicin insensitivity in MCF-7Dox/R, an isolated resistant-subline of MCF-7 (breast adenocarcinoma cell line). Effect of curcumin, a natural phytochemical in restoring doxorubicin sensitivity by targeting Aurora A was assessed furthermore. Methods: A doxorubicin resistant subline (MCF-7Dox/R) was isolated from the parental MCF-7 cells by treating the cell with gradual step-wise increasing concentration of the drug. Expressions of Aurora A and its target proteins (Akt, IκBα and NFκB) were assessed in both parental and MCF-7Dox/R cells. Both the cell lines were pretreated with curcumin prior to doxorubicin treatment. Cellular proliferation rate was measured using BrdU (5-bromo-2'-deoxyuridine) assay kit. Intracellular doxorubicin accumulation was estimated spectrofluorimetrically. Cellular uptake of curcumin (spectrophotometric and spectrofluorimetric method) and its nuclear localization was confirmed by confocal microscopic study. Protein expressions were determined by western blot analysis. Localization of Aurora A was ascertained by immunofluorescence assay. To explore the possible outcome of impact of curcumin on Aurora A, cell-cycle distribution and apoptosis were performed subsequently. Results: Higher expressions of Aurora A in MCF-7Dox/R cells led to phosphorylation of Akt as well as IκBα. Phosphorylated IκBα preceded release of NFκB. Phospho-Akt, NFκB consequentially decreased doxorubicin accumulation by enhancing the expressions of ABCG2 and Pgp1 respectively. Curcumin by regulating Aurora A and its target molecules sensitized resistant subline towards doxorubicin mediated G2/M-arrest and apoptosis. Conclusion: Molecular targeting of Aurora A by curcumin restores chemosensitivity by increasing the efficacy of doxorubicin in breast cancer.

The clinical scenario of acquired cisplatin resistance is considered as a major impediment in cervical cancer treatment. Bulky drug-DNA adducts formed by cisplatin elicits DNA damage response (DDR) which either subsequently induces apoptosis in the cervical cancer cells or enables them to adapt with drug assault by invigorating pro-survival molecular cascades. When HPV infected cervical cancer cells encounter cisplatin, a complex molecular interaction between deregulated tumor suppressors, DNA damage-repair enzymes, and prosurvival molecules get initiated. Ambiguous molecular triggers allow cancer cells to cull apoptosis by opting for a survival fate. Overriding of the apoptotic cues by the pro-survival cues renders a cisplatin resistant phenotype in the tumor microenvironment. The present review undrapes the impact of deregulated signaling nexus formed due to crosstalk of the key molecules related to cell survival and apoptosis in orchestrating platinum resistance in cervical cancer.

Background/Aim: Compromised cell-cycle checkpoint is a major obstacle for rendering radiotherapeutic success of radioresistant cells. Aspirin (ASA), an anti-inflammatory agent was repurposed previously for improving radiotherapy by limiting radiation toxicity. However, the underlying mechanism was unclear. The present study aimed to identify the mechanism of ASA mediated reversal of radioresistance in cervical cancer cells. Methods: Radioresistant subline SiHa/RR was developed from parental cervical squamous carcinoma cell line SiHa by chronic fractionated irradiation (IR). The radioresistance property of SiHa/RR was confirmed by clonogenic assay. Alteration in cell-cycle by ASA was determined by flow cytometry. ASA induced nuclear damage as consequence of mitotic catastrophe was confirmed by microscopic observation. The interaction between ASA and G2/M regulators was explored through in silico docking analysis and expressional change of them was affirmed by western blotting. Immunofluorescence study to examine Aurora Kinase A localization in presence and absence of ASA treatment was conducted. Finally the radiosensitizing ability of ASA was verified by apoptotic parameters (flow cytometrically and by western blotting). Result: Higher colony forming ability of SiHa/RR compared to SiHa became restrained upon ASA (5μM) treatment prior to IR. Flow cytometric analysis of ASA treated cells showed increased G2/M population followed by enlargement of cells displaying giant multinucleated morphology; typical characteristics of mitotic catastrophe. Underlying noteworthy mechanisms involved decreased expressions of G2/M regulatory proteins (Cyclin B1, CDK1, Aurora A Kinase, pAurora A Kinase) in IR/ASA along with inhibiting nuclear localization of Aurora Kinase A in SiHa/RR. Docking results also supported the findings. Prolonged treatment (12 h) with ASA led to apoptosis by altering expressions of Bcl2, Bax and Cytochrome C; which was achieved through the event of mitotic catastrophe. Conclusion: This work established that G2/M arrest and mitotic catastrophe can be considered as the principle mechanism of restoration of radiosensitivity in SiHa/RR by ASA pretreatment.

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