title: mTOR inhibitors synergize on regression, reversal of gene expression, and autophagy in hepatocellular carcinoma.
abstract: Hepatocellular carcinoma (HCC) affects more than half a million people worldwide and is the third most common cause of cancer deaths. Because mammalian target of rapamycin (mTOR) signaling is up-regulated in 50% of HCCs, we compared the effects of the U.S. Food and Drug Administration-approved mTOR-allosteric inhibitor, RAD001, with a new-generation phosphatidylinositol 3-kinase/mTOR adenosine triphosphate-site competitive inhibitor, BEZ235. Unexpectedly, the two drugs acted synergistically in inhibiting the proliferation of cultured HCC cells. The synergistic effect closely paralleled eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) dephosphorylation, which is implicated in the suppression of tumor cell proliferation. In a mouse model approximating human HCC, the drugs in combination, but not singly, induced a marked regression in tumor burden. However, in the tumor, BEZ235 alone was as effective as the combination in inhibiting 4E-BP1 phosphorylation, which suggests that additional target(s) may also be involved. Microarray analyses revealed a large number of genes that reverted to normal liver tissue expression in mice treated with both drugs, but not either drug alone. These analyses also revealed the down-regulation of autophagy genes in tumors compared to normal liver. Moreover, in HCC patients, altered expression of autophagy genes was associated with poor prognosis. Consistent with these findings, the drug combination had a profound effect on UNC51-like kinase 1 (ULK1) dephosphorylation and autophagy in culture, independent of 4E-BP1, and in parallel induced tumor mitophagy, a tumor suppressor process in liver. These observations have led to an investigator-initiated phase 1B-2 dose escalation trial with RAD001 combined with BEZ235 in patients with HCC and other advanced solid tumors.
authors.affiliation: Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, OH 45215, USA.
authors.forename: Hala Elnakat
authors.initials: HE
authors.lastname: Thomas
authors.forename: Carol A
authors.initials: CA
authors.lastname: Mercer
authors.forename: Larissa S
authors.initials: LS
authors.lastname: Carnevalli
authors.forename: Jongsun
authors.initials: J
authors.lastname: Park
authors.forename: Jesper B
authors.initials: JB
authors.lastname: Andersen
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Conner
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tanaka
authors.forename: Tomoo
authors.initials: T
authors.lastname: Matsutani
authors.forename: Akio
authors.initials: A
authors.lastname: Iwanami
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Aronow
authors.forename: Liu
authors.initials: L
authors.lastname: Manway
authors.forename: S Michel
authors.initials: SM
authors.lastname: Maira
authors.forename: Snorri S
authors.initials: SS
authors.lastname: Thorgeirsson
authors.forename: Paul S
authors.initials: PS
authors.lastname: Mischel
authors.forename: George
authors.initials: G
authors.lastname: Thomas
authors.forename: Sara C
authors.initials: SC
authors.lastname: Kozma
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001343:Autophagy / Q000187:drug effects; D000071189:Autophagy-Related Protein-1 Homolog; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism; D000068338:Everolimus; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology / Q000627:therapeutic use*; D015151:Immunoblotting; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011804:Quinolines / Q000494:pharmacology / Q000627:therapeutic use*; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*
chemical_list: D000970:Antineoplastic Agents; D007093:Imidazoles; D011804:Quinolines; D000068338:Everolimus; D000071189:Autophagy-Related Protein-1 Homolog; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; C112444:Ulk1 protein, mouse; C531198:dactolisib; D020123:Sirolimus