In vivo phosphoproteomics reveals kinase activity profiles that predict treatment outcome in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) lacks prognostic and predictive markers. Here, we use high-throughput phosphoproteomics to build a functional TNBC taxonomy. A cluster of 159 phosphosites is upregulated in relapsed cases of a training set (n = 34 patients), with 11 hyperactive kinases accounting for this phosphoprofile. A mass-spectrometry-to-immunohistochemistry translation step, assessing 2 independent validation sets, reveals 6 kinases with preserved independent prognostic value. The kinases split the validation set into two patterns: one without hyperactive kinases being associated with a >90% relapse-free rate, and the other one showing ≥1 hyperactive kinase and being associated with an up to 9.5-fold higher relapse risk. Each kinase pattern encompasses different mutational patterns, simplifying mutation-based taxonomy. Drug regimens designed based on these 6 kinases show promising antitumour activity in TNBC cell lines and patient-derived xenografts. In summary, the present study elucidates phosphosites and kinases implicated in TNBC and suggests a target-based clinical classification system for TNBC.

Cyclin C stimulates ß-cell proliferation in rat and human pancreatic ß-cells.

Activation of pancreatic ß-cell proliferation has been proposed as an approach to replace reduced functional ß-cell mass in diabetes. Quiescent fibroblasts exit from G0 (quiescence) to G1 through pRb phosphorylation mediated by cyclin C/cdk3 complexes. Overexpression of cyclin D1, D2, D3, or cyclin E induces pancreatic ß-cell proliferation. We hypothesized that cyclin C overexpression would induce ß-cell proliferation through G0 exit, thus being a potential therapeutic target to recover functional ß-cell mass. We used isolated rat and human islets transduced with adenovirus expressing cyclin C. We measured multiple markers of proliferation: [(3)H]thymidine incorporation, BrdU incorporation and staining, and Ki67 staining. Furthermore, we detected ß-cell death by TUNEL, ß-cell differentiation by RT-PCR, and ß-cell function by glucose-stimulated insulin secretion. Interestingly, we have found that cyclin C increases rat and human ß-cell proliferation. This augmented proliferation did not induce ß-cell death, dedifferentiation, or dysfunction in rat or human islets. Our results indicate that cyclin C is a potential target for inducing ß-cell regeneration.