Molecular analysis of the PI3K‐AKT pathway in uterine cervical neoplasia: Frequent PIK3CA amplification and AKT phosphorylation

Abstract

Uterine cervical carcinogenesis is probably dependent on cellular genetic damage in addition to the integration of high-risk HPV DNA in the epithelial cell genome. Gain of chromosome 3q24-29 is commonly observed in cervical neoplasia. The putative oncogene PIK3CA located in this region encodes a phosphatidylinositol 3-kinase (PI3K). In a process reversed by PTEN, PI3K generates inositol phospholipids that trigger AKT phosphorylation, which in turn effects tumor driving signals. We studied 46 specimens of formalin-fixed, paraffin-embedded cervical neoplastic tissue. The activation state of the PI3K-AKT pathway was assessed immunohistochemically using an antibody with specificity towards serine 473-phosphorylated AKT. AKT phosphorylation was found in 39 out of 46 examined specimens. To examine the possible molecular basis for this activation, we searched for PIK3CA amplification using quantitative real-time polymerase chain reaction. PIK3CA gene copy number was estimated to be 3 or more in 28 out of 40 successfully examined cases. Further, a PTEN mutation analysis of all 9 PTEN exons was carried out, but except for 1 metastasis with an exon 9 V369I heterozygosity, all cases showed normal PTEN sequence. Immunohistochemical staining for PTEN was strong in all lesions. In conclusion, an increased activation state of AKT kinase appears to be present in cervical carcinogenesis, and may be accounted for by PIK3CA amplification, whereas PTEN mutation seems to be of little importance. ' 2005 Wiley-Liss, Inc.Key words: cervical cancer; AKT; PIK3CA; PTEN; quantitative realtime PCR Cervical carcinoma is the second most common cancer in women world-wide. 1 High-risk human papillomavirus (HPV) DNA present in the neoplastic cells plays a causative role. 2 Integration of HPV DNA in the epithelial cell genome is accompanied by expression of the viral gene products E6 and E7 that abrogate the Rb and p53 tumor suppressor pathways, increase telomerase activity, and give rise to mitotic defects and numerical and structural chromosome instability. 3-5 Both E6 and E7 are required for the neoplastic process and they cooperate to immortalize human genital keratinocytes. 6 Even so, only a small proportion of highrisk HPV-positive lesions eventually progress to carcinoma, indicating that accumulation of additional genetic events in the host cell is needed for malignant conversion. 3,4 Cervical carcinomas show a recurrent pattern of cytogenetic instability where a gain of the long arm of chromosome 3 is commonly observed. [7][8][9][10][11] The same aberration has been demonstrated in HPV-transfected keratinocytes, pre-malignant cervical precursor lesions and cervical cancer cell lines. 7 , 8 , 12-14 By comparative genomic hybridization (CGH), the areas of gain have been refined to parts of chromosomal bands 3q24-29. 9-11 , 15 A possible oncogene in this region is PIK3CA at 3q26.3, encoding the p110a catalytic subunit of class IA phosphatidylinositol 3-kinase (PI3K). 16 Upon activation by receptor tyrosine kinases, PI3K generates inosito...

The epidermal growth factor receptor pathway in relation to pelvic lymph node metastasis and survival in early-stage cervical cancer

“…In our study, no relation between loss of PTEN and activation of the AKT pathway was found. Our low percentage (5.3%) of pAKT-positive cases is in contrast to previous studies in cervical cancer that used the same antibody and staining protocol but observed 29% to 94% pAKT-positive cases [22][23][24]. A major difference between these studies and our study is that we assessed pAKT in a much larges series (310 vs 31) of earlystage cervical cancer patients.…”

“…Loss of PTEN can be due to mutations, deletions, gene promoter methylation, or microRNAs (miRs) [25][26][27][28]. Mutations and deletions of PTEN are rare events in cervical cancer [16,22,29]. In a study by Yang et al, PTEN methylation was observed in 20 (15.7%) of 127 cervical cancers, whereas Cheung et al [16] reported PTEN methylation in 36 (58%) of 62 of squamous cell cervical cancers.…”

Increased phosphorylation of p70 S6 kinase is associated with HPV16 infection in cervical cancer and esophageal cancer

“…Recent studies also found that amplification of the PIK3CA gene accompanied by serine 473 phosphorylation of AKT is common in cervical cancers and it seems to be an independent event to HPV infection (Ma et al, 2000;Zhang et al, 2002;Bertelsen et al, 2006). Under our current condition, only 9.8% of cervical cancers and 6.2% of esophageal cancers were pAkt positive.…”

Molecular targets for therapeutic interventions in human papillomavirus-related cancers (Review)

“…Akt is equally attractive as mTOR for molecular targeting in therapeutics due to its participation in important cellular functions, including cell cycle progression, gene transcription and translation, apoptosis and cellular metabolism. Bertelsen et al (43) observed that in cervical carcinogenesis there was an increased activation of Akt due to PI3KCA gene amplification, raising the intracellular levels of PI3K. The mechanism of Akt activation by amplification of PIK3CA was also demonstrated in anal squamous cell carcinoma.…”