Piperine, a bioactive alkaloid, is known to have anticancer activities. Hence, in this study, the effectiveness of piperine pretreatment as a strategy for radio‐sensitizing colorectal adenocarcinoma cell line (HT‐29) was analyzed. For this, HT‐29 cells were pretreated with piperine (12.5 and 25 µg/mL) and exposed to γ‐radiation (1.25 Gy) and analyzed for various effector pathways to elucidate the possible mode of action in comparison to individual treatments. The proliferation efficiency of the cells was analyzed by trypan blue dye exclusion assay and MTT assay. The synergistic effects of the combination treatment were analyzed with compuSyn software. Downstream signaling pathways leading to apoptosis were studied using flowcytometry, immunofluorescence, and immunoblot assays. It was observed that combination treatment arrested HT‐29 cells at G2/M phase nearly 2.8 folds higher than radiation treatment alone, inducing the radio‐resistant cells to undergo apoptosis through mitochondria‐dependent pathway. In addition, activation of caspase‐3 and cleavage of poly(ADP‐ribose) polymerases‐1, the key molecular events in apoptotic signaling, were significantly enhanced. Activation of estrogen receptor beta (ERβ), a nuclear hormone transcription factor promoting tumor suppression represents a novel clinical advance towards management and prevention of cancers. Interestingly, the expression of ERβ was increased in the cells treated with piperine. In conclusion, piperine pretreatment enhances radio‐sensitization in HT‐29 cells by inducing the cells to undergo apoptosis hence, can be used as a classic candidate for colon cancer sensitization towards radiotherapy. Practical Application Piperine induces enhanced radiosensitization of colon cancer cell line (HT‐29) by interfering with the cancer cell line proliferation, DNA damage, and apoptosis.

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Background Lung cancer is a major constrain that increases mortality globally. Radiotherapy is one of the treatment modalities against lung cancer. A high dose of targeted radiation is required to achieve the treatment efficacy of cell killing. After radiotherapy, eventual tumor progression and therapy resistance are still a consequence of patient who undertakes nonsurgical radiation therapy. Piperine, a plant alkaloid, has been known to enhance the action of the anticancer drugs in various drug-resistant cancer cells. The aim of the current in vitro study was to study the effect of piperine on radiosensitizing property against A549 cells. Methods In vitro radiosensitizing activity of piperine was elucidated on A549 cells using MTT (3-(4, 5-dimethylthiazol-2-yl)-25-diphenyltetrazolium bromide) assay. CompuSyn analysis was used to compute the combination index values to analyze the combinatory effect of piperine and radiation Results and Conclusion We observed that piperine increased tumor cell killing in combination with the γ-radiation in vitro. However, further studies are warranted to understand the molecular mechanism of the radiosensitizing action of piperine.

Background Gamma radiation(γ) and other DNA targeted compounds generate highly lethal DNA double-stranded breaks (DSBs) inducing the cells to undergo apoptosis. Non-homologous end joining (NHEJ), one of the primary DSB repair pathways, plays an important role in providing cancer cells resistance against radio/chemotherapeutic agents resulting in cancer progression and relapse. Downregulating DNA-PK, a key protein in NHEJ could result in the accretion of DSBs, thereby sensitizing the cells towards radiation. Methods Cytotoxicity assays, Clonogenic assays, DNA damage assays, Flowcytometry analysis, Confocal Microscopy, immunofluorescence, and Immunoblotting were carried out. Combinatorial index calculations were done using Compusyn Analysis and data analysis was done using one-way ANOVA and two-way ANOVA, where a p-value of ≤ 0.0001 was considered significant. Results Here we found that the treatment of MCF7 cells with piperine, lead to the accumulation of DSBs induced by γ-radiation through lowering DNA-PK complex (comprising of DNA-PKcs/Ku70/Ku80), by altering the estrogen receptor (ER) α /β ratio. Piperine lowered DNA-PK mediated NHEJ repair through its transcription factor, ERα. Upregulation of ERβ, a nuclear hormone transcription factor promoting tumor suppression positively correlated with lowered expression of ERα and DNA-PK marked by the accumulation of radiation-induced DSBs and DNA damage response, cell cycle arrest leading to the intrinsic pathway of apoptosis. Conclusion Breast Cancer cells may be sensitized to radiation by altering the expression of DNA-PKc Complex, a key dsDNA repair protein machinery through selective estrogen receptor modulation. This study proposes a new strategy for combating acquired radioresistance through estrogen receptor-mediated modulation of the NHEJ pathway.