Inhibition of mTOR in combination with doxorubicin in an experimental model of hepatocellular carcinoma.
OBJECTIVE
Hepatocellular carcinoma (HCC) is resistant to chemotherapy. We reported that sirolimus, an mTOR inhibitor, has antiangiogenic properties in HCC. Since antiangiogenic therapy may enhance chemotherapy effects, we tested the antitumorigenic properties of sirolimus combined with doxorubicin in experimental HCC.


METHODS
Morris Hepatoma (MH) cells were implanted into livers of syngeneic rats. Animals were assigned to sirolimus, pegylated liposomal doxorubicin, both combined or control groups. Tumoral growth was followed by MRI. Antiangiogenic effects were assessed by CD31 immunostaining and capillary tube formation assays. Cell proliferation was monitored in vitro by thymidine incorporation. Expression of p21 and phosphorylated MAPKAP kinase-2 was quantified by immunoblotting.


RESULTS
Animals treated with the combination developed smaller tumors with decreased tumor microvessel density compared to animals that received monotherapies. In vitro, inhibition of mTOR further impaired capillary formation in the presence of doxorubicin. Doxorubicin reduced endothelial cell proliferation; inhibition of mTOR accentuated this effect. Doxorubicin stimulated p21 expression and the phosphorylation of MAPKAP kinase-2 in endothelial cells. Addition of mTOR inhibitor down-regulated p21, but did not decrease MAPKAP kinase-2 phosphorylation.


CONCLUSIONS
Sirolimus has additive antitumoral and antiangiogenic effects when administered with doxorubicin. These findings offer a rationale for combining mTOR inhibitors with chemotherapy in HCC treatment.
Piguet
Anne-Christine
AC
Institute of Clinical Pharmacology, University of Berne, Berne, Switzerland.
Semela
David
D
Keogh
Adrian
A
Wilkens
Ludwig
L
Stroka
Deborah
D
Stoupis
Christoforos
C
St-Pierre
Marie V
MV
Dufour
Jean-François
JF
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D001011:Aorta / Q000166:cytology; D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000473:pathology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004317:Doxorubicin / Q000031:analogs & derivatives* / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D009368:Neoplasm Transplantation; D015689:Oncogene Protein p21(ras) / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011092:Polyethylene Glycols / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D011912:Rats, Inbred ACI; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D014157:Transcription Factors / Q000037:antagonists & inhibitors*; D000099190:MAP-Kinase-Activated Kinase 2
D000903:Antibiotics, Antineoplastic; D004317:Doxorubicin; D047908:Intracellular Signaling Peptides and Proteins; D015689:Oncogene Protein p21(ras); D011092:Polyethylene Glycols; D017346:Protein Serine-Threonine Kinases; D020123:Sirolimus; D014157:Transcription Factors; D000099190:MAP-Kinase-Activated Kinase 2; C519510:Crtc1 protein, rat; C506643:liposomal doxorubicin; C401859:temsirolimus