PD0332991 (palbociclib/Ibrance®) is a cyclin-dependent kinase (CDK)4/6 inhibitor that has recently been approved for the treatment of estrogen receptor‑positive advanced breast cancer. The present study investigated the antiproliferative effects of PD0332991 on gastric cancer (GC) cells and the underlying molecular mechanisms. The activity of PD0332991 was tested in several GC cell lines, including AGS, KATO‑Ⅲ, NCI‑N87 and HS746T. Growth inhibitory activity of PD0332991, alone or in combination with fluorouracil (5‑FU), was measured by MTT assay. The effects of PD0332991 on cell cycle progression were analyzed by flow cytometry and western blotting. Protein pathway array and Ingenuity Pathway Analysis were used to identify signaling pathways that may mediate the antiproliferative effects of PD0332991. PD0332991 inhibited proliferation in a dose‑dependent manner and enhanced the activity of 5‑FU in all GC cell lines tested. Cells treated with PD0332991 exhibited cell cycle arrest in G1 phase of the cell cycle, whereas the number of cells in G2/M phase was decreased. PD0332991 also inhibited CDK6‑specific phosphorylation of retinoblastoma on Ser780, reduced the expression of cyclin D1, and induced expression of p53 and p27. Furthermore, 31 proteins were identified, the expression of which was significantly altered following treatment with PD0332991 in at least three cell lines. Pathway analysis indicated that the altered proteins were frequently associated with cell death, cell cycle and the molecular mechanism of cancer. The results of the present study indicated that PD0332991 may inhibit cell proliferation via modulation of the cell cycle, and may affect numerous oncogenic signaling pathways. Therefore, PD0332991 may be considered effective for the treatment of GC.

It is not known whether brain‑derived neurotrophic factor (BDNF) protects hippocampal neurons from high glucose‑induced apoptosis and/or synaptic plasticity dysfunction. The present study aimed to assess whether BDNF exerted a neuroprotective effect in rat hippocampal neurons exposed to high glucose and examine the underlying mechanisms. The apoptosis of primary hippocampal neurons was assessed by Annexin V‑fluorescein isothiocyanate/propidium iodide staining. The mRNA and protein expression levels were measured by reverse transcription‑-quantitative polymerase chain reaction and western blot experiments, respectively. Synaptic plasticity was evaluated by the immunolocalization of synaptophysin (Syn). Exposure of the hippocampal neurons to high glucose (75 mM for 72 h) resulted in cell apoptosis, decreased mRNA and protein expression levels of three synaptic plasticity‑related proteins (Syn, Arc and cyclic AMP response element‑binding protein), and changes in the cellular distribution of Syn, indicating loss of synaptic density. These effects of high glucose were partially or completely reversed by prior administration of BDNF (50 ng/ml for 24 h). Pre‑treatment with wortmannin, a phosphatidylinositol‑3‑kinase (PI3K) inhibitor, suppressed the ability of BDNF to inhibit the effects of high glucose. In addition, BDNF significantly upregulated the tropomyosin‑related kinase B, its cognate receptor, Akt and phosphorylated Akt at the protein levels under high glucose conditions. In conclusion, high glucose induced apoptosis and downregulated synaptic plasticity‑related proteins in hippocampal neurons. These effects were reversed by BDNF via the PI3K/Akt signaling pathway.