Hispidulin mediates apoptosis in human renal cell carcinoma by inducing ceramide accumulation
Authors: Ming-Quan Gao
Hui Gao
Yan-Tao Han
Jian-Jun Peng
Mei Han
Kai-Li Liu
Journal: Acta pharmacologica Sinica (2017)
Discipline: PHARMACOLOGY & TOXICOLOGY
Keywords: Hispidulin; anti-tumor effects; apoptosis induction; cell cycle arrest; clear-cell renal cell carcinoma
Affiliations: Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao 266021, China., College of Life Sciences, Chongqing Normal University, Chongqing 401331, China., Medical College, Qingdao University, Qingdao 266071, China.

Abstract:  Hispidulin, a polyphenolic flavonoid extracted from the traditional Chinese medicinal plant S involucrata, exhibits anti-tumor effects in a wide array of human cancer cells, mainly through growth inhibition, apoptosis induction and cell cycle arrest. However, its precise anticancer mechanisms remain unclear. In this study, we investigated the molecular mechanisms that contribute to hispidulin-induced apoptosis of human clear-cell renal cell carcinoma (ccRCC) lines Caki-2 and ACHN. Hispidulin (10, 20 μmol/L) decreased the viability of ccRCC cells in dose- and time-dependent manners without affecting that of normal tubular epithelial cells. Moreover, hispidulin treatment dose-dependently increased the levels of cleaved caspase-8 and caspase-9, but the inhibitors of caspase-8 and caspase-9 only partly abrogated hispidulin-induced apoptosis, suggesting that hispidulin triggered apoptosis via both extrinsic and intrinsic pathways. Moreover, hispidulin treatment significantly inhibited the activity of sphingosine kinase 1 (SphK1) and consequently promoted ceramide accumulation, thus leading to apoptosis of the cancer cells, whereas pretreatment with K6PC-5, an activator of SphK1, or overexpression of SphK1 significantly attenuated the anti-proliferative and pro-apoptotic effects of hispidulin. In addition, hispidulin treatment dose-dependently activated ROS/JNK signaling and led to cell apoptosis. We further demonstrated in Caki-2 xenograft nude mice that injection of hispidulin (20, 40 mg·kg-1·d-1, ip) dose-dependently suppressed tumor growth accompanied by decreased SphK1 activity and increased ceramide accumulation in tumor tissues. Our findings reveal a new explanation for the anti-tumor mechanisms of hispidulin, and suggest that SphK1 and ceramide may serve as potential therapeutic targets for the treatment of ccRCC. 

Retracted: Yes

PubPeer comments:
  Figure 5. Repressing SphK1 expression or inhibiting SphK1 activity enhances the anti-growth and proapoptotic effects of hispidulin. ... (C) Effect of hispidulin on cell apoptosis after SphK1 knockdown or pretreatment with a SphK1 inhibitor as examined by flow cytometry . ![file] On close inspection, two panels only differ in the inclusion of a small array of points added near the axis intersection, without even altering the percentages per quadrant. ![file] Another pair of panels with only one difference (and the same quadrant percentages): ![file] Two more pairs of panels with only local differences, e.g. a fiesta of clone-stamping in the upper right quadrant. ![file] , 
 Comparing Fig 8C (left) with Fig 6A from [Gao et al (2017)] . ![file] Could the authors clarify whether the bottom right panel is stained for p-JNK-1 2 or Cleaved PARP? , 
 5C, this time marked up... ![file] ...for comparison with 5G of [Pan et al (2016)] . ![file] , 
 Retracted [7 September 2021] . ------------------------------- The Editor-in-Chief has retracted this article. Concerns were raised regarding a number of figures, specifically: - Figure 5C: two panels (SKI-II and SphK1 siRNA for Caki-2) appear to be nearly identical - Figure 5C: the Caki-2 Control panel appears to be nearly identical to the ACHN SKI-II panel. - Figure 5C: the Caki-2 panel for His (20u2009u00b5mol l) appears to be nearly identical to the ACHN panel for His+SKI-II. - Figure 5C: the Caki-2 panel for His+SKI-II appears to be nearly identical to the ACHN panel for His-SphK1 siRN. - Figure 5C appears to partially overlap with Figure 5G of [1]. - Figure 6C: the TUNEL Control, TUNEL His (40u2009mg kg) panels and the p-JNK1 2 His (40u2009mg kg panels appear to have been previously published as the TUNEL Control, TUNEL His (40u2009mg kg) and cleaved PARP His (40u2009mg kg) panels of Figure 4C of [2]. The Editor-in-Chief therefore no longer has confidence in the reliability of the data reported in the article. References 1. Pan X, Wang H, Tong D, Wang C, Sun L, Zhao C, et al. Physcion induces apoptosis in hepatocellular carcinoma by modulating miR-370. Am J Cancer Res. 2016;6:2919u201331. 2. Gao MQ, Gao H, Han M, Liu KL, Peng JJ, Han YT. Hispidulin suppresses tumor growth and metastasis in renal cell carcinoma by modulating ceramide-sphingosine 1-phosphate rheostat. Am J Cancer Res. 2017;7:1501u201314. (Retraction published Am J Cancer Res. 2020 Jun 01;10(6):1921). ,