riccardin-d and Breast-Neoplasms

RDD648, a novel derivative of a natural molecule riccardin D, exhibited potent anticancer activity by targeting lysosomes in vitro and in vivo. Mechanistic studies revealed that RDD648 facilitated STAT3 to translocate into the nucleus, and this activity was involved in lysosome-mediated cell death as evidenced by our finding that inhibition of STAT3 alleviated lysosomal membrane permeabilization. Further investigation indicated that nuclear STAT3 directly interacted with transcription factor TFEB, leading to the partial loss of function of TFEB, which is essential for lysosome turnover. The present study first uncovers that STAT3 contributes to lysosomal-mediated cell death in RDD648-treated breast cancer cells though interacting with TFEB, and the findings may be significant in the design of treatments for breast cancers where STAT3 is constitutively expressed.

Topics: Animals; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Breast Neoplasms; Cell Death; Dose-Response Relationship, Drug; Endoplasmic Reticulum Stress; Female; Humans; Lysosomes; MCF-7 Cells; Mice; Mice, Inbred BALB C; Mice, Nude; Phenyl Ethers; STAT3 Transcription Factor; Stilbenes

Riccardin D, a liverwort-derived naturally occurring macrocyclic bisbibenzyl, has been found to exert anticancer effects in multiple cancer cell types. In this study, we investigated the effect and mechanism of Riccardin D on human breast cancer. Experiments were performed on human breast cancer MCF-7 and MDA-MB-231 cells. The antitumour effects of Riccardin D were assessed by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and human breast cancer xenografts mice model. TRAPeze(®) XL Telomerase Detection assay was used for the detection of telomerase activity. γ-H2 AX foci formation was tested for the induction of DNA damage response. Cell cycle distribution was analysed by flow cytometry, and cell apoptosis was determined by annexin V-FITC/PI staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay and Western blotting. Riccardin D effectively inhibited the growth of MCF-7 and MDA-MB-231 cells in vitro. And Riccardin D also effectively delayed the growth of MCF-7 and MDA-MB-231-luc-D3H2LN xenografts without significant loss of body-weight. Further analysis suggested that Riccardin D's effects may arise from its suppression of telomerase activity, which led to telomere dysfunction. Telomerase inhibition and telomere dysfunction could activate the canonical ataxia telangiectasia-mutated (ATM) kinase-mediated DNA damage response, as shown by elevated expression of γ-H2 AX, p-ATM and p-Chk2. This is finally followed by the induction of cell cycle arrest and apoptosis, as shown by the increase of TUNEL-stained cells, caspase activation, PARP cleavage and the increase of bax/bcl-2 ratio. Moreover, Riccardin D induced p53-proficient MCF-7 cells to arrest in G1 phase and p53-deficient MDA-MB-231 cells to arrest in G2/M phase. Overall, these results demonstrate that Riccardin D may inhibit human breast cancer growth through suppression of telomerase activity.

Topics: Animals; Antineoplastic Agents, Phytogenic; Blotting, Western; Breast Neoplasms; Cell Line, Tumor; Female; Fluorescent Antibody Technique; Humans; In Situ Nick-End Labeling; MCF-7 Cells; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Transplantation; Phenyl Ethers; Real-Time Polymerase Chain Reaction; Stilbenes; Telomerase