eIF4E-Overexpression imparts perillyl alcohol and rapamycin-mediated regulation of telomerase reverse transcriptase.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
perillyl alcohol (POH) | decrease | eIF4E-binding protein (4E-BP1) | Cancer cells | - | dephosphorylate | #1 |
perillyl alcohol (POH) | decrease | cap-dependent translation | Cancer cells | - | attenuate | #2 |
rapamycin | decrease | eIF4E-binding protein (4E-BP1) | Cancer cells | - | dephosphorylate | #3 |
rapamycin | decrease | cap-dependent translation | Cancer cells | - | attenuate | #4 |
perillyl alcohol (POH) | neutral | telomerase activity | cancer cell lines with elevated eIF4E | - | regulate | #5 |
rapamycin | neutral | telomerase activity | cancer cell lines with elevated eIF4E | - | regulate | #6 |
- | increase | eIF4E amounts | rb4E cells | 5-fold | 5-fold higher | #7 |
- | no change | telomerase activity | control and rb4E cells | - | nearly equivalent | #8 |
- | no change | telomerase reverse transcriptase (TERT) mRNA | control and rb4E cells | - | nearly equivalent | #9 |
- | no change | TERT protein | control and rb4E cells | - | nearly equivalent | #10 |
perillyl alcohol (POH) | no change | telomerase activity | control cells | - | unaffected | #11 |
perillyl alcohol (POH) | no change | TERT mRNA | control cells | - | unaffected | #12 |
perillyl alcohol (POH) | no change | TERT protein levels | control cells | - | unaffected | #13 |
rapamycin | no change | telomerase activity | control cells | - | unaffected | #14 |
rapamycin | no change | TERT mRNA | control cells | - | unaffected | #15 |
rapamycin | no change | TERT protein levels | control cells | - | unaffected | #16 |
perillyl alcohol (POH) | decrease | telomerase activity | rb4E cells | - | attenuated | #17 |
perillyl alcohol (POH) | decrease | TERT protein | rb4E cells | - | attenuated | #18 |
rapamycin | decrease | telomerase activity | rb4E cells | - | attenuated | #19 |
rapamycin | decrease | TERT protein | rb4E cells | - | attenuated | #20 |
perillyl alcohol (POH) | no change | TERT mRNA | rb4E cells | - | without corresponding decreases | #21 |
rapamycin | no change | TERT mRNA | rb4E cells | - | without corresponding decreases | #22 |
mTOR mediators | neutral | S6K | cells with increased eIF4E | - | modulated | #23 |
mTOR mediators | neutral | Akt | cells with increased eIF4E | - | modulated | #24 |
mTOR mediators | neutral | 4E-BP1 | cells with increased eIF4E | - | modulated | #25 |
perillyl alcohol (POH) | decrease | telomerase | rb4E cells | - | enables inhibitory effects | #26 |
perillyl alcohol (POH) | decrease | TERT protein | rb4E cells | - | enables inhibitory effects | #27 |
rapamycin | decrease | telomerase | rb4E cells | - | enables inhibitory effects | #28 |
rapamycin | decrease | TERT protein | rb4E cells | - | enables inhibitory effects | #29 |
eIF4E-overexpression | neutral | cellular protein synthetic processes | rb4E cells | - | modifies | #30 |
eIF4E-overexpression | neutral | gene regulation | rb4E cells | - | modifies | #31 |
Translation is mediated partly by regulation of free eukaryotic initiation factor 4E (eIF4E) levels through PI3K-Akt-mTOR signaling. Cancer cells treated with the plant-derived perillyl alcohol (POH) or the mechanistic target of rapamycin (mTOR) inhibitor rapamycin dephosphorylate eIF4E-binding protein (4E-BP1) and attenuate cap-dependent translation. We previously showed in cancer cell lines with elevated eIF4E that POH and rapamycin regulate telomerase activity through this pathway. Here, immortalized Chinese hamster ovary (CHO) control cells and CHO cells with forced eIF4E expression (rb4E) were used to elucidate eIF4E's role in telomerase regulation by POH and rapamycin. Despite 5-fold higher eIF4E amounts in rb4E, telomerase activity, telomerase reverse transcriptase (TERT) mRNA, and TERT protein were nearly equivalent in control and rb4E cells. In control cells, telomerase activity, TERT mRNA and protein levels were unaffected by either compound. In contrast, telomerase activity and TERT protein were both attenuated by either agent in rb4E cells, but without corresponding TERT mRNA decreases indicating a translational/post-translational process. S6K, Akt, and 4E-BP1 were modulated by mTOR mediators only in the presence of increased eIF4E. Thus, eIF4E-overexpression in rb4E cells enables inhibitory effects of POH and rapamycin on telomerase and TERT protein. Importantly, eIF4E-overexpression modifies cellular protein synthetic processes and gene regulation.