Researchers from Dana-Farber characterized an HR-positive breast cancer cell line that is resistant to treatment with CDK4/6 inhibitors, and they demonstrated that these cells have alterations in the RB-pathway, including loss of the retinoblastoma protein, higher levels of p107, CDK2 and cyclin E2
, and lower levels of the estrogen receptor.
Spermine ingestion significantly increased the gene expressions of cyclin A2 (Group SP-3 d vs Group Con-3 d; Group SP-6 d vs Group Con-6 d; Group SP-9 d vs Group Con-9 d) but markedly decreased mRNA expressions of p21 (Group SP-6 d vs Group Con-6 d; Group SP-9 d vs Group Con-9 d), cyclin D3 (Group SP-6 d vs Group Con-6 d), and cyclin E2 (Group SP-6 d vs Group Con-6 d; p<0.05).
As shown in Figure 2, in the spleen, gene expression of cyclin A2 (Group SP-3 d vs Group Con-3 d; Group SP-6 d vs Group Con-6 d; Group SP-9 d vs Group Con-9 d) significantly increased but p21 (Group SP-3 d relative to Group Con-3 d) and cyclin D3 (Group SP-9 d relative to Group Con-9 d) markedly decreased (p<0.05), and no significant difference was found in cyclin E2 mRNA abundance that was induced by spermine intake (p>0.05).
Kanget al., "Cyclin E2
overexpression is associated with endocrine resistance but not insensitivity to CDK2 inhibition in human breast cancer cells," Molecular Cancer Therapeutics, vol.
Polyclonal antibodies against p16-INK4A, cyclin E2, and p53 and monoclonal antibodies against cyclin D1 and p21-CIP1 were purchased from Cell Signaling Technology (Danvers, MA, USA).
The protein content of these complexes, that is, CDK2, cyclin E2, CDK4, and cyclin D1, was significantly decreased in the senescent cells (Figures 5(b2) and (b3)); and, as a result, the phosphorylation of pRB was also significantly inhibited (Figure 5(b4)).
We further found that CcNe1 (cyclin E1), CCNE2 (cyclin E2), and CDK2 were all upregulated, while CDKN1A (P21) and CDKN1B (P27) were downregulated in tumor samples.
Downregulated p21 and p27 do not inhibit cyclin E1 and cyclin E2 from forming cyclin E-CDK2 complexes with CDK2.
Symbol Gene name 1 CCNA1 Cyclin A1 2 CCNA2 Cyclin A2 3 CCNB1 Cyclin B1 4 CCND1 Cyclin D1 5 CCND2 Cyclin D2 6 CCND3 Cyclin D3 7 CCNE1 Cyclin E1 8 CCNE2 Cyclin E2
9 CCNH Cyclin H 10 CDC25A Cell division cycle 25 homolog A (S.
The protein content of these complexes, that is, CDK2, cyclin E2
, CDK4, and cyclin D1, was significantly decreased in the senescent cells (B-2 and B-3); and, as a result, the phosphorylation of pRB was also significantly inhibited (B4).
Antibodies against Bach1 (sc-14700), Bcl2 (sc-7382), Bcl-xL (sc-8392), HO-1 (sc-1796), cyclin D1 (sc-20044), cyclin E2 (sc-28351), cyclin B1 (sc-595), CDK2 (sc-163), CDK4 (sc-601), CDK6 (sc-177), p21 (sc-397), p53 (sc-126), the human Bach1 siRNA (sc-37064), and the control siRNA were obtained from Santa Cruz Biotechnology (Santa Cruz, CA).
Cyclin E2 levels were significantly greater in Ad-Bach1 HMVECs but decreased markedly when the cells were treated with NAC (Figures 6(a) and 6(b)).