Constitutively activated PI3K accelerates tumor initiation and modifies histopathology of breast cancer (original) (raw)
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Cancer Research, 2009
Phosphatidylinositol 3-kinases (PI3K) constitute important regulators of various signaling pathways with relevance in cancer. Enhanced activation of p110A, the catalytic subunit of PI3K, was found in a high proportion of many human tumor types. We generated a mouse model in which PI3K is activated by forced recruitment of p110A to the membrane. Different transgenic lines expressing myristoylated p110A protein under the control of the epithelial-specific mouse mammary tumor virus promoter were selected according to different levels of PI3K activity and characterized. Delayed mammary gland involution and morphologic changes of the mammary ducts could be detected in young transgenic female mice. These changes were more pronounced in old animals, especially in mutiparous females, in which we observed increased ductal branching, alveolar hyperplasia, and intraductal neoplasia. We also observed a small percentage of mammary tumors. Crosses of myrp110A transgenic mice with heterozygous p53(+/À) knockout mice resulted in neither enhanced tumorigenesis nor in a stronger mammary gland phenotype. However, the CDK4 activating mutation (R24C) lead to increased tumorigenesis in transgenic myrp110A mice, emphasizing the postulated perturbation of the interaction of the CDK4/Rb/E2F cascade and the PI3K signaling in many human cancers. Interestingly, in tumors of myrp110A transgenic mice, we observed an increased phosphorylation of the estrogen receptor-A, a typical feature of human breast cancer. The model presented here will help to discover additional factors which influence the progression of preneoplastic lesions to tumors in the mammary gland and to explore antitumor therapies based on PI3K or estrogen receptor-A pathway inhibition.
Cancer Res, 2008
Phosphatidylinositol 3-kinases (PI3K) constitute important regulators of various signaling pathways with relevance in cancer. Enhanced activation of p110A, the catalytic subunit of PI3K, was found in a high proportion of many human tumor types. We generated a mouse model in which PI3K is activated by forced recruitment of p110A to the membrane. Different transgenic lines expressing myristoylated p110A protein under the control of the epithelial-specific mouse mammary tumor virus promoter were selected according to different levels of PI3K activity and characterized. Delayed mammary gland involution and morphologic changes of the mammary ducts could be detected in young transgenic female mice. These changes were more pronounced in old animals, especially in mutiparous females, in which we observed increased ductal branching, alveolar hyperplasia, and intraductal neoplasia. We also observed a small percentage of mammary tumors. Crosses of myrp110A transgenic mice with heterozygous p53(+/À) knockout mice resulted in neither enhanced tumorigenesis nor in a stronger mammary gland phenotype. However, the CDK4 activating mutation (R24C) lead to increased tumorigenesis in transgenic myrp110A mice, emphasizing the postulated perturbation of the interaction of the CDK4/Rb/E2F cascade and the PI3K signaling in many human cancers. Interestingly, in tumors of myrp110A transgenic mice, we observed an increased phosphorylation of the estrogen receptor-A, a typical feature of human breast cancer. The model presented here will help to discover additional factors which influence the progression of preneoplastic lesions to tumors in the mammary gland and to explore antitumor therapies based on PI3K or estrogen receptor-A pathway inhibition.
2008
Phosphatidylinositol 3-kinases (PI3K) constitute important regulators of various signaling pathways with relevance in cancer. Enhanced activation of p110A, the catalytic subunit of PI3K, was found in a high proportion of many human tumor types. We generated a mouse model in which PI3K is activated by forced recruitment of p110A to the membrane. Different transgenic lines expressing myristoylated p110A protein under the control of the epithelial-specific mouse mammary tumor virus promoter were selected according to different levels of PI3K activity and characterized. Delayed mammary gland involution and morphologic changes of the mammary ducts could be detected in young transgenic female mice. These changes were more pronounced in old animals, especially in mutiparous females, in which we observed increased ductal branching, alveolar hyperplasia, and intraductal neoplasia. We also observed a small percentage of mammary tumors. Crosses of myrp110A transgenic mice with heterozygous p53(+/À) knockout mice resulted in neither enhanced tumorigenesis nor in a stronger mammary gland phenotype. However, the CDK4 activating mutation (R24C) lead to increased tumorigenesis in transgenic myrp110A mice, emphasizing the postulated perturbation of the interaction of the CDK4/Rb/E2F cascade and the PI3K signaling in many human cancers. Interestingly, in tumors of myrp110A transgenic mice, we observed an increased phosphorylation of the estrogen receptor-A, a typical feature of human breast cancer. The model presented here will help to discover additional factors which influence the progression of preneoplastic lesions to tumors in the mammary gland and to explore antitumor therapies based on PI3K or estrogen receptor-A pathway inhibition.
Cooperation between Pik3ca and p53 Mutations in Mouse Mammary Tumor Formation
Cancer Research, 2011
PIK3CA, which codes for the p110a catalytic subunit of phosphatidylinositol 3-kinase, is one of the most frequently mutated genes in human breast cancer. Here, we describe a mouse model for PIK3CA-induced breast cancer by using the ROSA26 (R26) knock-in system, in which targeted Pik3ca alleles can be activated through transgenic expression of Cre recombinase. We mated Pik3ca H1047R and Pik3ca wt knock-in lines with MMTV-Cre transgenics, which express Cre in mammary epithelium. Starting at approximately 5 months of age, female R26-Pik3ca H1047R ;MMTV-Cre mice, but not control R26-Pik3ca wt ;MMTV-Cre mice, developed mammary tumors, as well as lymphoid and skin malignancies. R26-Pik3ca H1047R ;MMTV-Cre mammary tumors were typically either adenosquamous carcinoma or adenomyoepithelioma. As p53 is the most commonly mutated gene in breast cancer, we tested for genetic interaction between Pik3ca H1047R and p53 loss-of-function mutations in R26-Pik3ca H1047R ;p53 loxP/þ ;MMTV-Cre mice. This led to decreased survival of double-mutant animals, which developed lymphoma and mammary tumors with rapid kinetics. Mammary tumors that formed in p53 loxP/þ ; MMTV-Cre conditional mutants were either poorly differentiated adenocarcinoma or spindle cell/EMT, whereas R26-Pik3ca H1047R ;p53 loxP/þ ;MMTV-Cre mammary tumors were mostly adenosquamous carcinoma or spindle cell/EMT indicating that double-mutant mice develop a distinct spectrum of mammary tumors. Thus, an oncogenic variant of PIK3CA implicated in multiple human breast cancer subtypes can induce a very diverse spectrum of mammary tumors in mice. Furthermore, Pik3ca H1047R shows cooperation with p53, which altered the specific tumors that formed. Thus, the two most frequently mutated genes in human breast cancer show cooperation in mammary tumor formation. Cancer Res; 71(7); 2706-17. Ó2011 AACR.
Oncogene, 2012
Oncogenic mutations in PIK3CA, which encodes the phosphoinositide-3-kinase (PI3K) catalytic subunit p110α, occur in ∼25% of human breast cancers. In this study, we report the development of a knock-in mouse model for breast cancer where the endogenous Pik3ca allele was modified to allow tissue-specific conditional expression of a frequently found Pik3ca(H1047R) (Pik3ca(e20H1047R)) mutant allele. We found that activation of the latent Pik3ca(H1047R) allele resulted in breast tumors with multiple histological types. Whole-exome analysis of the Pik3ca(H1047R)-driven mammary tumors identified multiple mutations, including Trp53 mutations that appeared spontaneously during the development of adenocarinoma and spindle cell tumors. Further, we used this model to test the efficacy of GDC-0941, a PI3K inhibitor, in clinical development, and showed that the tumors respond to PI3K inhibition.Oncogene advance online publication, 27 February 2012; doi:10.1038/onc.2012.53.
Breast Cancer-Associated PIK3CA Mutations Are Oncogenic in Mammary Epithelial Cells
Cancer Research, 2005
Activation of the phosphoinositide 3-kinase (PI3K) pathway has been implicated in the pathogenesis of a variety of cancers. Recently, mutations in the gene encoding the p110A catalytic subunit of PI3K (PIK3CA) have been identified in several human cancers. The mutations primarily result in single amino acid substitutions, with >85% of the mutations in either exon 9 or 20. Multiple studies have shown that these mutations are observed in 18% to 40% of breast cancers. However, the phenotypic effects of these PIK3CA mutations have not been examined in breast epithelial cells. Herein, we examine the activity of the two most common variants, E545K and H1047R, in the MCF-10A immortalized breast epithelial cell line. Both variants display higher PI3K activity than wild-type p110A yet remain sensitive to pharmacologic PI3K inhibition. In addition, expression of p110A mutants in mammary epithelial cells induces multiple phenotypic alterations characteristic of breast tumor cells, including anchorage-independent proliferation in soft agar, growth factor-independent proliferation, and protection from anoikis. Expression of these mutant p110A isoforms also confers increased resistance to paclitaxel and induces abnormal mammary acinar morphogenesis in three-dimensional basement membrane cultures. Together, these data support the notion that the cancer-associated mutations in PIK3CA may significantly contribute to breast cancer pathogenesis and represent attractive targets for therapeutic inhibition. (Cancer Res 2005; 65(23): 10992-11000) Note: S. J. Isakoff and J.A. Engelman contributed equally to this work. Requests for reprints: Joan S. Brugge,
Plos One, 2012
PIK3CA, the gene coding for the p110a subunit of phosphoinositide 3-kinase, is frequently mutated in a variety of human tumors including breast cancers. To better understand the role of mutant PIK3CA in the initiation and/or progression of breast cancer, we have generated mice with a conditional knock-in of the common activating mutation, Pik3ca H1047R , into one allele of the endogenous gene in the mammary gland. These mice developed a ductal anaplasia and hyperplasia by 6 weeks of age characterized by multi-layering of the epithelial lining of the mammary ducts and expansion of the luminal progenitor (Lin 2 ; CD29 lo ; CD24 + ; CD61 + ) cell population. The Pik3ca H1047R expressing mice eventually develop mammary tumors with 100% penetrance but with a long latency (.12 months). This is significantly longer than has been reported for transgenic models where expression of the mutant Pik3ca is driven by an exogenous promoter. Histological analysis of the tumors formed revealed predominantly ERa-positive fibroadenomas, carcinosarcomas and sarcomas. In vitro induction of Pik3ca H1047R in immortalized mammary epithelial cells also resulted in tumor formation when injected into the mammary fat pad of immunodeficient recipient mice. This novel model, which reproduces the scenario of a heterozygous somatic mutation occurring in the endogenous PIK3CA gene, will thus be a valuable tool for investigating the role of Pik3ca H1047R mutation in mammary tumorigenesis both in vivo and in vitro.
PLOS One, 2012
PIK3CA, the gene coding for the p110a subunit of phosphoinositide 3-kinase, is frequently mutated in a variety of human tumors including breast cancers. To better understand the role of mutant PIK3CA in the initiation and/or progression of breast cancer, we have generated mice with a conditional knock-in of the common activating mutation, Pik3ca H1047R , into one allele of the endogenous gene in the mammary gland. These mice developed a ductal anaplasia and hyperplasia by 6 weeks of age characterized by multi-layering of the epithelial lining of the mammary ducts and expansion of the luminal progenitor (Lin 2 ; CD29 lo ; CD24 + ; CD61 + ) cell population. The Pik3ca H1047R expressing mice eventually develop mammary tumors with 100% penetrance but with a long latency (.12 months). This is significantly longer than has been reported for transgenic models where expression of the mutant Pik3ca is driven by an exogenous promoter. Histological analysis of the tumors formed revealed predominantly ERa-positive fibroadenomas, carcinosarcomas and sarcomas. In vitro induction of Pik3ca H1047R in immortalized mammary epithelial cells also resulted in tumor formation when injected into the mammary fat pad of immunodeficient recipient mice. This novel model, which reproduces the scenario of a heterozygous somatic mutation occurring in the endogenous PIK3CA gene, will thus be a valuable tool for investigating the role of Pik3ca H1047R mutation in mammary tumorigenesis both in vivo and in vitro.
Characterization of a Tumor-Associated Activating Mutation of the p110β PI 3-Kinase
PLoS ONE, 2013
The PI3-kinase pathway is commonly activated in tumors, most often by loss of PTEN lipid phosphatase activity or the amplification or mutation of p110a. Oncogenic mutants have commonly been found in p110a, but rarely in any of the other catalytic subunits of class I PI3-kinases. We here characterize a p110b helical domain mutation, E633K, first identified in a Her2-positive breast cancer. The mutation increases basal p110b activity, but does not affect activation of p85/p110b dimers by phosphopeptides or Gbc. Expression of the mutant causes increases in Akt and S6K1 activation, transformation, chemotaxis, proliferation and survival in low serum. E633 is conserved among class I PI3 Ks, and its mutation in p110b is also activating. Interestingly, the E633K mutant occurs near a region that interacts with membranes in activated PI 3-kinases, and its mutation abrogates the requirement for an intact Ras-binding domain in p110b-mediated transformation. We propose that the E633K mutant activates p110b by enhancing its basal association with membranes. This study presents the first analysis of an activating oncogenic mutation of p110b.