Phosphatidylinositol 3-Kinase Inhibition by LY294002 Radiosensitizes Human Cervical Cancer Cell Lines

Abstract

Purpose: 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). Experimental Design: Cervical cancer cells were treated separately and concurrently with the PI3K inhibitor LY294002 (10 Amol/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 (1log 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.

Increased expression of pAKT is associated with radiation resistance in cervical cancer

“…Also, their conclusion that only increased HER2 expression associated with improved OS is quite an opposite conclusion to the previous paper (Nakano et al, 1997). In addition, Lee suggested that 'PI3K inhibition radiosensitises cervix cancer' in his recent publication (Lee et al, 2006).…”

“…Phosphoinositide-3-kinase catalytic alpha, involved in the PI3K/ AKT-signalling pathway, is known to be an oncogene associated with cervical cancer (Ma et al, 2000). In addition, the PI3K catalytic subunit is amplified in cervical cancer, and the inhibition of PI3K by LY294002 radiosensitises human cervical cancer cell lines (Lee et al, 2006). Therefore, we thought it would be worthwhile to investigate the components of PI3K/AKT pathway in cervical cancer.…”

PTEN/pAkt/p53 signaling pathway correlates with the radioresponse of non-small cell lung cancer

“…One factor known to increase tumor cell resistance to radiation, the importance of PI3K/AKT targeting for overcoming resistance of tumors to radiotherapy, has been tested in vitro and in vivo and the results indicate this cascade is a promising target (24)(25)(26). The activation of Akt plays a critical role in fundamental cellular functions such as cell proliferation and survival by phosphorylation of a variety of substrates (36)(37)(38).…”

A novel HDAC inhibitor OBP-801 and a PI3K inhibitor LY294002 synergistically induce apoptosis via the suppression of survivin and XIAP in renal cell carcinoma

“…The PI3K-Akt signaling pathway is a key regulator of cell growth through many downstream targets. Therefore, the PI3K inhibitor LY294002 can inhibit cell growth and cause apoptosis also in RCC cells (11)(12)(13)(14)(15) Previous reports showed that co-treatment with an HDAC inhibitor and a PI3K inhibitor was effective against ovarian cancer, cervical cancer, non-small cell lung cancer, colon cancer, chronic myeloid leukemia and cutaneous T-cell lymphoma by downregulating XIAP and Mcl-1 (16)(17)(18)(19)(20)(21). The PI3K-Akt pathway is well known to be upregulated in most RCC, but the combination of a PI3K inhibitor and an HDAC inhibitor has not been examined in RCC cells.…”