Correlations of mRNA expression and in vitro chemosensitivity to enzastaurin in freshly explanted human tumor cells.
OBJECTIVE
Enzastaurin (LY317615) is a novel serine/threonine kinase inhibitor, targeting Protein Kinase C-beta (PKC-beta), and PI3K/AKT pathways to inhibit angiogenesis and tumor cell proliferation. The aims of this study were to determine whether Enzastaurin has direct antitumor activity against freshly explanted tumor cells and to correlate mRNA expression of genes related to the proposed mechanism of action of enzastaurin with in vitro chemosensitivity.


METHODS
Freshly biopsied tumor cells were studied using soft-agar cell cloning experiments (SACCE) to determine the in vitro chemosensitivity to enzastaurin. An aliquot of the same tumor specimens was shock-frozen and total RNA was isolated for standardized multiplex rt-PCR experiments for gene expression of PKC-beta1, PKC-beta2, IL-8, IL-8RA, IL-8RB, Glycogen Synthase Kinase 3 beta (GSK-3beta) and TGF-beta1. Correlations, threshold optimization, sensitivity, specificity, and efficiency were analyzed using the appropriate statistical methodologies.


RESULTS
Seventy-two tumor samples were collected and 63 were fully evaluable. Low levels of mRNA expression of GSK-3beta and high levels of mRNA expression of IL-8 were highly significantly correlated with chemosensitivity to enzastaurin. Optimization analyses demonstrated threshold values of 4,000 copies for IL-8 and three copies for GSK-3beta relative to 10(4) copies of beta-actin. However, no correlation between mRNA expression of PKC-beta1, PKC-beta2, IL-8RA, IL-8RB and chemosensitivity to enzastaurin was observed. Expression of TGF-beta1 mRNA was not detectable in the specimens investigated.


CONCLUSIONS
mRNA expression levels of IL-8 and GSK-3beta correlate with antitumor activity of enzastaurin. These results form a rational basis for clinical trials to evaluate the expression of these genes as potential predictors for treatment outcome after enzastaurin chemotherapy.
Hanauske
Axel-Rainer
AR
St. Georg Hospital, Lohmühlenstr. 5, 20099 Hamburg, Germany. Hanauske.ind-synergen@t-online.de
Eismann
Ulrike
U
Oberschmidt
Olaf
O
Pospisil
Heike
H
Hanauske-Abel
Hartmut M
HM
Blatter
Johannes
J
Ma
Doreen
D
Chen
Victor
V
Lahn
Michael
M
D000970:Antineoplastic Agents / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D015870:Gene Expression; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D009369:Neoplasms / Q000188:drug therapy*; D012333:RNA, Messenger / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D007211:Indoles; D016209:Interleukin-8; D012333:RNA, Messenger; D038362:Glycogen Synthase Kinase 3; C504878:enzastaurin