Phosphatidylinositol 3-kinase inhibition by LY294002 radiosensitizes human cervical cancer cell lines.
OBJECTIVE
The phosphatidylinositol 3-kinase (PI3K) catalytic subunit is amplified in cervical cancers, implicating PI3K in cervical carcinogenesis. We evaluated the radiosensitizing effect of PI3K inhibition by LY294002 on clonogenic survival, growth characteristics, and gene expression in cervical cancer cell lines (HeLa and CaSki).


METHODS
Cervical cancer cells were treated separately and concurrently with the PI3K inhibitor LY294002 (10 micromol/L) and radiation (2 Gy) with serial analysis of cell count, apoptosis, and flow cytometry. PI3K inhibition was assessed by protein analysis of phosphorylated Akt. Clonogenic assays were done with varying doses of radiation and LY294002 and varied time points of administration of LY294002 proximate to the radiation dose. Surviving fractions and dose modification factors (DMF) were calculated. Each experiment was done in triplicate and analyzed using ANOVA regression analysis and Dunnett's t Test. Microarray gene expression analysis was done on the HeLa cell line.


RESULTS
PI3K inhibition with LY294002 alone did not decrease cell survival. However, treatment with LY294002 significantly radiosensitized HeLa and CaSki cell lines with DMFs (1 log cell kill) of 1.95 and 1.37, respectively. Compared with post-irradiation, pretreatment produced more radiosensitization (P < 0.0001). DMFs were 2.2, 2.0, 2.0, and 1.2 for LY294002 added at 6, 2, and 0.5 hours before irradiation and 6 hours after irradiation, respectively. LY294002 pretreatment in irradiated HeLa cells led to altered gene expression.


CONCLUSIONS
Although LY294002 alone did not produce cytotoxic effects, PI3K inhibition with LY294002 produced significant radiosensitization, showed significant time-dependent effects, increased apoptosis, and altered gene expression. These findings support future investigation of PI3K inhibitors in combination with radiation therapy for carcinoma of the cervix.
Lee
Christopher M
CM
Department of Radiation Oncology, University of Utah School of Medicine and Huntsman Cancer Hospital, Salt Lake City, Utah, USA.
Fuhrman
Christa B
CB
Planelles
Vicente
V
Peltier
Morgan R
MR
Gaffney
David K
DK
Soisson
Andrew P
AP
Dodson
Mark K
MK
Tolley
H Dennis
HD
Green
Christopher L
CL
Zempolich
Karen A
KA
D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002470:Cell Survival / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D009025:Morpholines / Q000494:pharmacology*; D020411:Oligonucleotide Array Sequence Analysis; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D002583:Uterine Cervical Neoplasms / Q000378:metabolism* / Q000628:therapy
D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D011838:Radiation-Sensitizing Agents; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases