In this study, we investigated the effect of the extracts from Vaccinium oldhamii on cell proliferation and the regulatory mechanisms of cyclin D1 protein level in human cancer cells. The branch extracts from Vaccinium oldhamii (VOB) showed higher inhibitor effect against the cell growth than leave extracts (VOL) and fruit extracts (VOF) in human colorectal cancer, breast cancer, prostate cancer, non-small lung cancer, pancreatic cancer and liver cancer cells. In addition, VOB decreased cyclin D1 level at both protein and mRNA level. MG132 treatment attenuated VOB-mediated cyclin D1 downregulation. A point mutation of threonine-286 to alanine attenuated cyclin D1 degradation by VOB. In addition, the inhibition of nuclear export by leptomycin B (LMB) attenuated cyclin D1 degradation by VOB. But, the treatment of PD98059 (ERK1/2 inhibitor), SB203580 (p38 inhibitor), SP600125 (JNK inhibitor), LiCl (GSK3β inhibitor), LY294002 (PI3K inhibitor) or BAY 11-7082 (IκK inhibitor) did not affect VOB-induced cyclin D1 degradation. In conclusion, VOB induced cyclin D1 degradation through redistribution of cyclin D1 from the nucleus to cytoplasm via T286 phosphorylation of cyclin D1, which resulted in the inhibition of cancer cell proliferation.

Abstract
 Introduction
 Materials and methods
  Materials
  Sample preparation
  Cell culture and treatment
  Cell proliferation assay
  SDS-PAGE and Western blot analysis
  Reverse transcriptase-polymerase chain reaction (RT-PCR)
  Expression vectors
  Statistical analysis
 Results and discussion
  Effect of VOB on the cell proliferation and cyclin D1expression in human cancer cells
  Induction of cyclin D1 proteasomal degradation by VOBin human cancer cells
  Contribution of threonine-286 (T286) phosphorylation ofcyclin D1 by VOB to cyclin D1 degradation
  Determination of upstream kinases associated withVOB-induced cyclin D1 degradation
 References

• Su Bin Park(Department of Medicinal Plant Resources, Andong National University)
• Ha Na Kim(Department of Medicinal Plant Resources, Andong National University)
• Gwang Hun Park(Forest Medicinal Resources Research Center, National Institute of Forest Science)
• Ho-Jun Son(Forest Medicinal Resources Research Center, National Institute of Forest Science)
• Hyun Ji Eo(Forest Medicinal Resources Research Center, National Institute of Forest Science)
• Jeong Ho Song(Forest Medicinal Resources Research Center, National Institute of Forest Science)
• Hun Min Song(Baekdudaegan National Arboretum)
• Ji Ae Park(Baekdudaegan National Arboretum)
• Jin Boo Jeong(Department of Medicinal Plant Resources, Andong National University) Corresponding author