Akt kinases in breast cancer and the results of adjuvant therapy

BACKGROUND: The serine/threonine kinase Akt, or protein kinase B, has recently been a focus of interest because of its activity to inhibit apoptosis. It mediates cell survival by acting as a transducer of signals from growth factor receptors that activate phosphatidylinositol 3-kinase. METHODS: We analysed the expression of the isoforms Akt1 and Akt2 as well as phosphorylated Akt (pAkt) by immunohistochemistry in frozen tumour samples from 280 postmenopausal patients who participated in a randomised trial comparing cyclophosphamide–methotrexate–5-fluorouracil chemotherapy and postoperative radiotherapy. The patients were simultaneously randomised to tamoxifen or to no endocrine treatment. RESULTS: Marked staining was found in 24% of the tumours for Akt1, but in only 4% for Akt2. A low frequency of Akt2-positive cells (1–10%) was observed in another 26% of the tumours. pAkt was significantly associated with both Akt1 and Akt2 expression. Overexpression of erbB2 correlated significantly with pAkt (P = 0.0028). The benefit from tamoxifen was analysed in oestrogen receptor (ER)-positive patients. Patients with a negative status of Akt (no overexpression of Akt1, Akt2 or pAkt) showed significant benefit from tamoxifen. The relative rate of distant recurrence, with versus without tamoxifen, was 0.44 (95% confidence interval [CI], 0.25–0.79) for ER+/Akt1- patients, while it was 0.72 (95% CI, 0.34–1.53) for ER+/Akt1+ patients. The difference in rate ratio did not reach statistical significance. The rate of locoregional recurrence was significantly decreased with radiotherapy versus chemotherapy for Akt-negative patients (rate ratio, 0.23; 95% CI, 0.08–0.67; P = 0.0074), while no benefit was evident for the Akt-positive subgroup (rate ratio, 0.77; 95% CI, 0.31–1.9; P = 0.58). The interaction between Akt and the efficacy of radiotherapy was significant in multivariate analysis (P = 0.042). CONCLUSION: Activation of the Akt pathway is correlated with erbB2 overexpression in breast cancer. The results suggest that Akt may predict the local control benefit from radiotherapy

Alterations in the PI3K/AKT Signaling Pathway and Response to Adjuvant Treatment in Breast Cancer

(PI3K)/AKT signaling pathway could be a cause of therapeutic resistance in breast cancer. The PI3K/AKT pathway controls cell proliferation, cell growth and survival, and its members include oncogenes and tumor suppressor genes. Alterations in this pathway are frequent in cancer. In this thesis, we aimed to study the biological significance of some of these alterations in a tumor context as well as their clinical value. PIK3CA gene, encoding the PI3K catalytic subunit, was examined for mutations. The tumor suppressor PTEN, that counteracts PI3Kmediated effects, was studied at the protein level whereas amplification of RPS6KB1 (S6K1) and RPS6KB2 (S6K2) genes, encoding two substrates of the mammalian target of rapamycin (mTOR) acting downstream PI3K/AKT, was also inspected. AKT phosphorylation or activation (pAKT) was determined by immunohistochemistry. Other factors related with this pathway, such as HER-2, heregulin (HRG) β1, the cell cycle inhibitor p21WAF1/CIP1, the pro-apoptotic factor Bcl-2, and cyclin D1,  were also considered. These studies were perfomed in two patient materials consisting of premenopausal patients that received endocrine treatment (paper I) and postmenopausal patients randomized to receive radiotherapy (RT) or chemotherapy (CMF) in combination with tamoxifen (Tam) or no endocrine treatment (papers II-IV). In the first material, we found that pAKT indicated higher risk of distant recurrence among endocrine treated patients. In the second material HRGβ1 induced accumulation cytoplasmic p21 in vitro and pAKT was associated with cytoplasmic p21 in the tumors. In addition, p21 cellular location identified subgroups of ER+ patients with different responses to tamoxifen. Other alterations such as PIK3CA mutations and PTEN loss were positively associated in this material. PIK3CA mutations lowered the risk for local recurrences while PTEN loss conferred radiosensitivity as a single variable or combined with mutated PIK3CA. PIK3CA mutations and/or PTEN loss was associated with lower S-phase (SPF). Nevertheless, among patients with low proliferating tumors, these alterations predicted higher risk of recurrence in contrast to those with high proliferating tumors. Finally, we found amplification of the S6K1 and S6K2 genes. S6K2 amplification was associated with cyclin D1 gene amplification, predicted poor recurrence-free survival and breast cancer death, and indicated benefit from tamoxifen. On the other hand, S6K1 amplification was associated with HER-2 amplification/overexpression, indicated higher risk of recurrence and was a predictor of poor response to radiotherapy. These results indicate the potential of this pathway as therapeutic source.  Bröstcancer är en vanlig sjukdom och dödsorsak bland kvinnor i Sverige. Könshormonet östrogen tillsammas med cellernas receptorer för hormonet spelar en viktig roll för bröstcancerutvecklingen. Därför behandlas denna sjukdom med anti-hormonella substanser inriktade mot hämning av östrogensyntes/östrogen receptorn. Tamoxifen är den vanligaste formen av anti-östrogenbehandling som används efter operation. Tamoxifenbehandling förbättrar betydligt 5-årsöverlevnaden hos patienter med östrogenreceptorpositiva tumörer. Emellertid finns det patienter som återkommer med metastaser efter en tid. I det här projektet studerar vi andra receptorer samt deras signalvägar som kan aktivera östrogenreceptorn och därmed orsaka tamoxifenresistens. En sådan receptor är HER-2 vilken överuttrycks i 15-20% vid bröstumörer. HER-2 receptorn kan rekrytera proteiner med enzymatisk aktivitet, till exempel PI3K. PI3K aktiverar ett annat enzym, AKT, vilket är inblandat i en kaskad som leder till tumörtillväxt och tumöröverlevnad (genom till exempel aktivering av östrogenreceptorn). Våra resultat hitills visar att patienter med aktiverat AKT (pAKT) har större risk att få metastaser och därmed sämre överlevnad än patienter utan pAKT, detta trots hormonell behandling. I större material där HER-2 proteinuttrycket korrelerar med pAKT har vi också funnit att patienter med AKTnegativa tumörer kunde dra nytta av både tamoxifen och strålbehandling. Vi har även undersökt PIK3CA genen (som kodar för en del av PI3K) och hittat mutationer i 24% av bröstumörerna. Det är dock ännu oklart hur dessa mutationer ska tas hänsyn till för att kunna bestämma en effektiv behandling. PTEN är ett annat enzym som motverkar PI3K-aktivitet. Bortfall av PTEN förekommer ofta i bröstcancer och  har associerats med PI3K/AKT aktivering. I vårt material var PTEN-förlust frekvent (37%) och associerades med PIK3CA mutationer. PTEN förlust som ensam faktor eller tillsammans med PIK3CA mutationer ökade strålkänslighet. Andra proteiner som är inblandade i PI3K signalvägen är S6K1 och S6K2 och dessa har betydelse för cellens proteinsyntes. Nyligen har vi kunnat visa att generna för både S6K1/2 finns i många kopior (genamplifering) I tumörcellerna hos bröstcancerpatienter. Dessutom fanns det ett positivt samband mellan S6K1/2 amplifiering och amplifiering av andra kända cancergener (som t. ex HER-2 och cyclin D1) men förhållandet till PIK3CA-mutationer var det omvända. Patienter med antigen S6K1 eller HER-2 amplifierade tumörer svarade dåligt på strålbehandling men skulle möjligen kunna behandlas med en specifik substans riktad mot S6K1 eller HER-2. Ett ökat antal kopior av S6K2 indikerade dålig prognos men bra nytta av tamoxifen. Våra resultat visar att PI3K/AKT signalvägen ofta är aktiverad vid bröstcancer och skulle kunna vara en viktig måltavla för behandling

Copyright: Elsevier

Akt2 expression is associated with good longter

Open Access

The mTOR effectors 4EBP1 and S6K2 are frequently coexpressed, and associated with a poor prognosis and endocrine resistance in breast cancer: a retrospective study including patients from the randomised Stockholm tamoxifen trial

The mTOR effectors 4EBP1 and S6K2 are frequently coexpressed, and associated with a poor prognosis and endocrine resistance in breast cancer : a retrospective study including patients from the randomised Stockholm tamoxifen trials.

INTRODUCTION: mTOR and its downstream effectors the 4E-binding protein 1 (4EBP1) and the p70 ribosomal S6 kinases (S6K1 and S6K2) are frequently upregulated in breast cancer, and assumed to be driving forces in tumourigenesis, in close connection with oestrogen receptor (ER) networks. Here, we investigated these factors as clinical markers in five different cohorts of breast cancer patients. METHODS: The prognostic significance of 4EBP1, S6K1 and S6K2 mRNA expression was assessed with real-time PCR in 93 tumours from the treatment randomised Stockholm trials, encompassing postmenopausal patients enrolled between 1976 and 1990. Three publicly available breast cancer cohorts were used to confirm the results. Furthermore, the predictive values of 4EBP1 and p4EBP1_S65 protein expression for both prognosis and endocrine treatment benefit were assessed by immunohistochemical analysis of 912 node-negative breast cancers from the Stockholm trials. RESULTS: S6K2 and 4EBP1 mRNA expression levels showed significant correlation and were associated with a poor outcome in all cohorts investigated. 4EBP1 protein was confirmed as an independent prognostic factor, especially in progesterone receptor (PgR)-expressing cancers. 4EBP1 protein expression was also associated with a poor response to endocrine treatment in the ER/PgR positive group. Cross-talk to genomic as well as non-genomic ER/PgR signalling may be involved and the results further support a combination of ER and mTOR signalling targeted therapies. CONCLUSION: This study suggests S6K2 and 4EBP1 as important factors for breast tumourigenesis, interplaying with hormone receptor signalling. We propose S6K2 and 4EBP1 as new potential clinical markers for prognosis and endocrine therapy response in breast cancer

http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69784 1 Clinical potential of the mTOR targets S6K1 and S6K2 in breast cancer

N.B.: When citing this work, cite the original article

Locoregional recurrence-free probability for patients treated with postoperative radiotherapy (RT) or cyclophosphamide–methotrexate–5-fluorouracil (CMF) chemotherapy in relation to Akt status

<p><b>Copyright information:</b></p><p>Taken from "Akt kinases in breast cancer and the results of adjuvant therapy"</p><p>Breast Cancer Research 2003;5(2):R37-R44.</p><p>Published online 20 Jan 2003</p><p>PMCID:PMC154147.</p><p>Copyright © 2003 Stål et al., licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any non-commercial purpose, provided this notice is preserved along with the article's original URL.</p

The mTOR effectors 4EBP1 and S6K2 are frequently coexpressed, and associated with a poor prognosis and endocrine resistance in breast cancer : a retrospective study including patients from the randomised Stockholm tamoxifen trials.

INTRODUCTION: mTOR and its downstream effectors the 4E-binding protein 1 (4EBP1) and the p70 ribosomal S6 kinases (S6K1 and S6K2) are frequently upregulated in breast cancer, and assumed to be driving forces in tumourigenesis, in close connection with oestrogen receptor (ER) networks. Here, we investigated these factors as clinical markers in five different cohorts of breast cancer patients. METHODS: The prognostic significance of 4EBP1, S6K1 and S6K2 mRNA expression was assessed with real-time PCR in 93 tumours from the treatment randomised Stockholm trials, encompassing postmenopausal patients enrolled between 1976 and 1990. Three publicly available breast cancer cohorts were used to confirm the results. Furthermore, the predictive values of 4EBP1 and p4EBP1_S65 protein expression for both prognosis and endocrine treatment benefit were assessed by immunohistochemical analysis of 912 node-negative breast cancers from the Stockholm trials. RESULTS: S6K2 and 4EBP1 mRNA expression levels showed significant correlation and were associated with a poor outcome in all cohorts investigated. 4EBP1 protein was confirmed as an independent prognostic factor, especially in progesterone receptor (PgR)-expressing cancers. 4EBP1 protein expression was also associated with a poor response to endocrine treatment in the ER/PgR positive group. Cross-talk to genomic as well as non-genomic ER/PgR signalling may be involved and the results further support a combination of ER and mTOR signalling targeted therapies. CONCLUSION: This study suggests S6K2 and 4EBP1 as important factors for breast tumourigenesis, interplaying with hormone receptor signalling. We propose S6K2 and 4EBP1 as new potential clinical markers for prognosis and endocrine therapy response in breast cancer