J Breast Cancer.  2010 Dec;13(4):337-348. 10.4048/jbc.2010.13.4.337.

Phosphorylated Akt and Phosphorylated mTOR Expression in Breast Invasive Carcinomas: Analysis of 530 Cases

• An J
• Jeong H
• Lee Y
• Woo SU
• Seo JH
• Kim A

• KMID: 2286521
• DOI: http://doi.org/10.4048/jbc.2010.13.4.337

Abstract

PURPOSE
The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway has a central role in regulation of cell proliferation, differentiation, motility and survival. This pathway has recently generated great interest because its elements are, potentially, novel targets for the treatment of various malignancies, including breast cancer.
METHODS
Using tissue microarray sections of breast carcinoma, we performed immunohistochemical studies using antibodies against the phosphorylated forms of Akt (p-Akt) and mTOR (p-mTOR) in 530 invasive breast carcinomas and 30 ductal carcinomas in situ (DCIS). We investigated possible associations between expression of these proteins and clinicopathologic characteristics and disease outcomes.
RESULTS
In 530 invasive carcinomas, weak and strong expression of p-Akt was observed in 180 (34.0%) and 288 (54.3%) cases, respectively. The expression of p-Akt was associated with expression of estrogen receptors (ER) (p=0.045), progesterone receptors (PR) (p=0.003), lymph node metastasis (p<0.001) and cancer stage (p=0.027). Weak and strong expression of p-mTOR was found in 136 (25.7%) and 207 (39.1%) cases, respectively. The mTOR pathway was more frequently activated in DCIS than in invasive breast carcinoma (p=0.001). p-mTOR expression was associated with expression of ER (p=0.040), PR (p=0.009), tumor size (p<0.001), and stage (p=0.002). In a univariate analysis, strong expression of p-Akt was associated with longer disease-free survival (DFS). In a multivariate analysis, neither p-Akt nor p-mTOR was associated with DFS.
CONCLUSION
The PI3K/Akt/mTOR pathway is active in DCIS as well as in invasive carcinoma of the breast. Our study also suggests that the PI3K/Akt/mTOR pathway is influenced by ER rather than erbB-2, and that this pathway may contribute more to cancer pathogenesis in ER-positive tumors.

Keyword

Breast; Carcinoma; mTOR protein; Proto-oncogene protein c-akt

MeSH Terms

Antibodies
Breast
Carcinoma, Ductal
Carcinoma, Intraductal, Noninfiltrating
Cell Proliferation
Disease-Free Survival
Lymph Nodes
Multivariate Analysis
Neoplasm Metastasis
Phosphatidylinositol 3-Kinase
Proteins
Receptors, Estrogen
Receptors, Progesterone
Sirolimus
TOR Serine-Threonine Kinases
Antibodies
Phosphatidylinositol 3-Kinase
Proteins
Receptors, Estrogen
Receptors, Progesterone
Sirolimus
TOR Serine-Threonine Kinases

Figure

• 

  Figure 1 Representative results of phosphorylated Akt (p-Akt) and phosphorylated mTOR (p-mTOR) immunohistochemical staining in samples of ductal carcinoma in situ (×400). (A) A sample with weak staining of p-Akt. (B) A sample with strong staining of p-Akt. (C) A sample with weak staining of p-mTOR. (D) A sample with strong staining of p-mTOR.

• 

  Figure 2 Representative results of phosphorylated Akt (p-Akt) and phosphorylated mTOR (p-mTOR) immunohistochemical staining in samples of invasive ductal carcinoma (×400). (A) A sample with weak staining of p-Akt. (B) A sample with strong staining of p-Akt. (C) A sample with weak staining of p-mTOR. (D) A sample with strong staining of p-mTOR.

• 

  Figure 3 Western blot validation of immunohistochemical staining of phosphorylated-mTOR (×400). (A) Positive bands in 3 human breast carcinoma cell lines and 4 cases of breast tumors were found on western blots. (B-E) In cases having 1-4 breast tumors, immunohistochemical staining of paraffin tissue is well correlated with bands on western blot analysis.

• 

  Figure 4 Kaplan-Meier plots with log-rank tests of disease-free survival (DFS) in invasive carcinomas in relation to different levels of p-Akt expression. The rate of DFS was significantly higher in patients with p-Akt strong-positive tumors than in those with p-Akt negative/weak-positive tumors (p=0.004).

• 

  Figure 5 Kaplan-Meier plots with log-rank tests of disease-free survival (DFS) in invasive carcinomas in relation to different levels of p-mTOR expression. In contrast to p-Akt, p-mTOR expression had no significant association with DFS (p=0.136).

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