The 17q23 amplicon is associated with poor outcome in ER+ breast cancers, but the causal genes to endocrine resistance in this amplicon are unclear. Here, we interrogate transcriptome data from primary breast tumors and find that among genes in 17q23, PRR11 is a key gene associated with a poor response to therapeutic estrogen suppression. PRR11 promotes estrogen-independent proliferation and confers endocrine resistance in ER+ breast cancers. Mechanistically, the proline-rich motif-mediated interaction of PRR11 with the p85α regulatory subunit of PI3K suppresses p85 homodimerization, thus enhancing insulin-stimulated binding of p110-p85α heterodimers to IRS1 and activation of PI3K. PRR11-amplified breast cancer cells rely on PIK3CA and are highly sensitive to PI3K inhibitors, suggesting that PRR11 amplification confers PI3K dependence. Finally, genetic and pharmacological inhibition of PI3K suppresses PRR11-mediated, estrogen-independent growth. These data suggest ER+/PRR11-amplified breast cancers as a novel subgroup of tumors that may benefit from treatment with PI3K inhibitors and antiestrogens.

Introduction Non-inferiority (NI) analysis is not usually considered in the early phases of clinical development. In some negative phase II trials, a post-hoc NI analysis justified additional phase III trials that were successful. However, the risk of false positive achievements was not controlled in these early phase analyses. We propose to preplan NI analyses in superiority-based Simon's two-stage designs to control type I and II error rates. Methods Simulations have been proposed to assess the control of type I and II errors rates with this method. A total of 12,768 two-stage Simon's design trials were constructed based on different assumptions of rejection response probability, desired response probability, type I and II errors, and NI margins. P-value and type II error were calculated with stochastic ordering using Uniformly Minimum Variance Unbiased Estimator. Type I and II errors were simulated using the Monte Carlo method. The agreement between calculated and simulated values was analyzed with Bland-Altman plots. Results We observed the same level of agreement between calculated and simulated type I and II errors from both two-stage Simon's superiority designs and designs in which NI analysis was allowed. Different examples has been proposed to explain the utility of this method. Conclusion Inclusion of NI analysis in superiority-based single-arm clinical trials may be useful for weighing additional factors such as safety, pharmacokinetics, pharmacodynamic, and biomarker data while assessing early efficacy. Implementation of this strategy can be achieved through simple adaptations to existing designs for one-arm phase II clinical trials.

<p>E2F4 gene signature modulation and association with overall survival in ER+/HER2- breast cancer treated with endocrine therapy. a) E2F4 gene signature expression at baseline (pre) and after 2-weeks of aromatase inhibitor treatment (post), data from ACOSOGZ1031b study. Tumors were divided according to the E2F4 score at baseline in high, medium or low tertiles. After two-weeks of aromatase inhibitor treatment, there was a decrease in the E2F4 score in all groups. However, the proportion of tumors still expressing a high post-treatment E2F4 score was greater in patients with a high E2F4 score at baseline (60%) than the other groups. b) Overall survival in patients with ER+ breast cancer treated with adjuvant endocrine therapy in the METABRIC database (n=1498) according to E2F4 signature score tertiles. c) Overall survival in patients with ER+ tumors from METABRIC according to E2F4 score tertiles in Luminal A and d) Luminal B tumors.</p>

<p>Distribution of clinically actionable mutations according to PEPI score, PCNA proliferation signature and breast cancer subtypes</p>