The Role of PTEN in Progression of Ductal Carcinoma in situ
|Institution:||Cedars-Sinai Medical Center|
Shikha Bose , M.D. -
|Award Cycle:||2002 (Cycle VIII)||Grant #: 8KB-0011||Award: $305,507|
|Award Type:||New Investigator Awards|
|Pathogenesis>Unraveling the path to breast cancer: tumor progression|
Initial Award Abstract (2002)
DCIS is an early lesion where the cancer cells are confined within the ducts of the breast. With the advent of better screening methods, the incidence of DCIS diagnosis is increasing. The most feared complication of DCIS is its tendency to invade out of the confines of the ducts and become invasive cancer. It is not known what genetic changes cause DCIS to become invasive. Thus, there is both a clinical and research need for better genetic markers that might predict, in each patient, whether DCIS is likely to become invasive cancer. This is a "quality of life" issue for the patient, because we want to spare women not at risk of invasive cancer the trauma of chemo- and radiation therapy. Our previous work, supported by a 2001 BCRP grant, identified that a gene called PTEN was a potential marker for DCIS progression. The PTEN protein works by modulating the activity of a potentially tumor-promoting signaling pathway inside of cancer cells, called PI3-kinase. Also, PTEN affects Akt-dependent cell survival signals, such that in the absence of active PTEN, tumor cells can avoid programmed cell death (apoptosis). We have recently demonstrated that there are reduced amounts of PTEN protein in 40% of invasive human breast cancers as compared to DCIS lesions, which show reduction in only 10% of cases. These numbers are reasonable, since we expect only a fraction of DCIS patients to progress to invasive cancer. This is supported by those DCIS lesions that are associated with invasive cancer, which show a similar reduction in PTEN as the nearby invasive cancer. Based on this observations, we hypothesize that reduction of PTEN protein levels confer to the DCIS cells the capability of invading tissues and spreading. Using BCRP support we will, first, examine a large cohort of 500 DCIS cases for the presence of abnormalities in the PTEN gene structure and expression. Other cell proliferation and invasion proteins regulated by PTEN will also be analyzed like cyclin D1 and a laminin receptor, the integrin subunit 6. Secondly, we will obtain DCIS lesions that have recurred as invasive cancer and perform the same set of tests on the original DCIS in order to compare with the recurrent lesion. The above assays for abnormal PTEN protein levels and structural alterations will be performed on a tissue microarray (i.e., a microchip containing tissues from hundreds of different cases) that has been recently developed. We are adapting this approach to be more specific for DCIS lesions. We also hope to develop a novel assay to test for structural alteration of the PTEN gene, which if successful, will potentially impact not only the testing in breast cancers but also in many cancers from different organs like the ovary, skin, prostate, brain and thyroid. We predict that the presence of PTEN defects in DCIS cases will be both associated with invasive cancer and in recurrent DCIS lesions. We aim to develop the methodology to advance these genetic marker tests for routine clinical evaluation on this type of early breast cancer.
Final Report (2006)
DCIS is an early cancerous lesion of the breast wherein the cancer cells are confined within the ducts of the breast. The most feared complication of DCIS is its tendency to invade out of the confines of the ducts and become invasive cancer. This happens in 25-30% of cases. With the advent of better screening methods, the incidence of DCIS lesions is increasing. It is not known how or why DCIS becomes invasive cancer. Knowledge of the genetic events causing invasion is crucial for the development of future modes of therapy to either stop or reverse the process and for the development of markers that might predict which DCIS is more likely to become invasive cancer, thus allowing individualized treatment protocols. PTEN is a recently identified gene that normally prevents tumor formation (tumor suppressor). Its role is currently being investigated in many cancers. Our initial studies indicate that PTEN may have an important role in causing invasion of DCIS lesion. We are currently investigating its use as a marker for predicting the development of subsequent invasion. We have created a tissue array containing about 300 cases of DCIS, approximately half of which are associated with invasive carcinoma. We tested this cohort of DCIS cases for the presence of abnormalities in the PTEN gene structure and expression. We used: (1) immunohistochemistry for studying protein expression, and (2) fluorescent in situ hybridization (FISH analysis) with a probe containing the PTEN gene for structural alterations (deletions) of the PTEN gene. Other proteins regulated by PTEN were also tested to study the role of the PTEN gene in DCIS lesions and to determine the role it has in causing these lesions to become invasive cancers. We have demonstrated for the first time that the Akt pathway is activated early in breast cancer, in the DCIS stage. 33%, 32%, 15% and 60% of DCIS showed overexpression (greater amounts) of p-Akt, p-FKHR, p-mTOR and cyclin D1. No statistical correlation was observed between PTEN loss and overexpression of Akt or its downstream proteins with the exception of p-S6. This indicates that activation of the Akt pathway was not a result of PTEN loss. Expression levels of PTEN and S6 were statistically significantly different in DCIS and invasive cancers indicating association with disease progression. Loss of the PTEN was noted in 11.5% of DCIS as compared to 26% of invasive cancers, while S6 overexpression was noted in 47% of DCIS and in 72% of invasive cancer. PTEN loss was seen in high grade tumors while cyclin D1 overexpression was noted in tumors with good prognostic features. Tumors expressing cyclin D 1 showed longer disease free survival rates. mTOR showed a three times greater risk for recurrence. Finally, a large proportion of in-situ and invasive breast cancers overexpressed cyclinD1 and activated S6. Our results have significant bearing in the design and implementation of clinical trials that would further study risk of DCIS progression at the genetic level. This will provide the clinician with informative markers to make treatment decisions, and provide insight into which proteins and genes might best be investigated for new drug development.
Symposium Abstract (2005)
The Akt pathway is an important regulator of cell proliferation and survival and is known to be deregulated in many cancers. The pathway has generated considerable interest in recent years due to the development of kinase inhibitors that are able to successfully reduce tumor growth. The relationship of the various component proteins of the pathway has been elucidated in detail in experimental models; however validation in humans is necessary for effective application of molecular therapies. Initial data suggests that inhibitors targeting constituent proteins of this pathway may be useful in treating breast cancer patients. This study was therefore conducted to determine the status of the AKT pathway in human breast cancers and the relationship between the different proteins and their activation levels. The tissue array is ideally suited for this purpose as it not only allows the study of a large number of breast cancer cases but also allows accurate determination of relationships between different proteins. Expression levels of the various constituent proteins of the Akt pathway (PTEN, Akt, FKHR, mTOR, S6 and cyclin D1) were evaluated by immunohistochemistry, on consecutive sections from a tissue microarray containing 145 cases of invasive breast cancers and 140 cases of pure ductal carcinoma in-situ (DCIS). Aberrant expression was correlated statistically with tumor characteristics and disease outcome. Certain significant differences were noted from experimental model systems. The Akt pathway was found to be activated early in breast cancer, in the DCIS stage, independent of PTEN loss. Loss of the PTEN protein was associated with disease progression from the DCIS stage to the invasive stage, and this appeared to occur through pathways independent of Akt. Additionally a large proportion of in-situ and invasive breast cancers overexpressed cyclinD1 and activated S6. This may have significant implications in the development and application of targeted therapy.
The Akt pathway in human breast cancer: a tissue-array-based analysis.
Authors: Bose S, Chandran S, Mirocha JM, Bose N
|Yr: 2006||Vol: 19||Nbr: 2||Abs:||Pg:238-45|