1 / 27

Joshua Ko School of Chinese Medicine Hong Kong Baptist University

Herbal diterpenoids pseudolaric acid B and triptolide induce growth arrest and apoptosis in colon cancer cells. Joshua Ko School of Chinese Medicine Hong Kong Baptist University. Pseudolaric acid B. Introduction.

royce
Download Presentation

Joshua Ko School of Chinese Medicine Hong Kong Baptist University

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Herbal diterpenoids pseudolaric acid B and triptolide induce growth arrest and apoptosis in colon cancer cells Joshua Ko School of Chinese Medicine Hong Kong Baptist University

  2. Pseudolaric acid B Introduction • Novel chemotherapeutic agents derived from active phytochemicals could be used as adjuvants and improve the anti-carcinogenicity of standard drug treatments. • These include the novel terpenoid pseudolaric acid B (PLAB) extracted from the root bark of the Chinese tree Pseudolarix kaempferi, which had shown potential cytotoxicity against several tumor cells.

  3. Triptolide Introduction • Another diterpene triepoxide triptolide isolated from the herb Tripterygium wilfordii hook f. has received supporting evidences for being a potential anti-neoplastic agent. • It was found that triptolide could inhibit the growth and metastasis of various solid tumors and is having synergistic action with conventional chemotherapeutic drugs. • However, triptolide also manifests a potent but non-specific cytotoxicity in a series of mammalian cells, which has precluded its further development into potential anti-neoplastic drug.

  4. Introduction • The discovery of specific molecular targets has become important in the development of new agents for chemoprevention and chemotherapy of cancer. • Among novel molecular targets of anti-carcinogenic agents, the nonsteroidal anti-inflammatory drug (NSAID)-activated gene (NAG-1) has been actively investigated in recent years.

  5. Introduction • It is a divergent member of the transforming growth factor- superfamily, which is recognized as an important negative regulator of colonic epithelial cell growth. • Thus, it has been proposed to be a potent tumor suppressor of human colorectal cancers.

  6. Objectives of present study • To investigate the actions of PAB in modulating the apoptotic and growth-inhibitory factors in human colon cancer cells, and to correlate with its regulation of NAG-1 expression. • The mode of action of PAB would be compared with that of the other diterpenoid triptolide to see if they share common molecular target(s) and act via similar pathway.

  7. PAB induces growth inhibition in HT-29 cells

  8. PAB inhibits cell proliferation in HT-29 cells (BrdU incorporation)

  9. 1200 1200 1200 900 Number 900 900 Number Number 600 600 600 300 300 300 0 0 0 0 50 100 150 200 250 0 50 100 150 200 250 0 50 100 150 200 250 Channels (PI-A) Channels (PI-A) Channels (PI-A) PAB induces cell cycle arrest in HT-29 cells PAB (µM) G0/G1 C G2/M S 1 5 25

  10. PAB modulates growth-related proteins in HT-29 cells 24 h 48 h 72 h PAB (µM) C C 1 5 25 C C 1 5 25 C C 1 5 25 c-myc Cyclin A Cyclin B1 β-Actin

  11. PAB induces DNA fragmentation in HT-29 cells (DNA laddering) M C C 1 5 25 PAB (µM)

  12. PAB promotes apoptosis in HT-29 cells (nuclear chromatin condensation) Control 1 µM 5 µM 25 µM Phase-contrast microscopy Control 1 µM 5 µM 25 µM Fluorescence microscopy with DAPI staining

  13. PAB promotes apoptosis in HT-29 cells (FACS analysis)

  14. PAB modulates apoptosis-related proteins in HT-29 cells 24 h 48 h 72 h PAB (µM) C C 1 5 25 C C 1 5 25 C C 1 5 25 Procas-pase-3 Bcl-xL PARP β-Actin

  15. PAB modulates apoptosis-related proteins in HT-29 cells 24 h 48 h 72 h PAB (µM) C C 1 5 25 C C 1 5 25 C C 1 5 25 COX-2 NAG-1 β-Actin

  16. PAB decreases COX-2 mRNA level in HT-29 cells (Real-time PCR) (with 20 µM PAB)

  17. PAB increases NAG-1 mRNA level in HT-29 cells (Real-time PCR) (with 20 µM PAB)

  18. PAB increases Egr-1 mRNA level in HT-29 cells (Real-time PCR) (with 20 µM PAB)

  19. Triptolide induces growth inhibition in HT-29 cells

  20. Triptolide induces cell cycle arrest in HT-29 cells Triptolide (nM) G0/G1 C G2/M S 5 10 20

  21. Triptolide induces DNA fragmentation in HT-29 cells (DNA laddering) M C C 10 15 20 Triptolide (nM)

  22. Triptolide promotes apoptosis in HT-29 cells (FACS analysis)

  23. Triptolide increases NAG-1 protein expression and mRNA level in HT-29 cells • 24 h 48 h 72 h Triptolide (nM) C 10 15 20 C 10 15 20 C 10 15 20 NAG-1 β-Actin (with 15 nM triptolide)

  24. Summary (1) • Marked growth-inhibitory and pro-apoptotic effects found in HT-29 colonic cancer cells treated with PAB. • G2/M phase arrest along with suppression of the growth-related protein c-myc and modulation of the associated cyclins. • The novel NAG-1 pathway has been proven to be one of the molecular targets that mediate the cytotoxic actions of PAB; Egr-1 may be another transcriptional factor that is responsible for the PAB-induced anti-tumorigenic action.

  25. Summary (2) • In spite of the inconsistent and somewhat ambiguous actions of triptolide, it is also well known for its high toxicity in human cells, resulting in a narrow therapeutic index.

  26. Conclusion The comparatively safer drug PAB would have a higher value for prospective study of its anti-tumor effects, with known molecular targets and precise mechanism of action.

  27. Acknowledgment Dr. Pauline Chiu Department of Chemistry The University of Hong Kong

More Related