Intraoperative Identification of Clavicle Fracture Patterns: Do Clavicles Fail in a Predictable Pattern?

OBJECTIVES: To characterize the fracture pattern and pattern of fragmentation for displaced, midshaft clavicle fractures undergoing operative management. DESIGN: Prospective observational study. SETTING: Two institutions. Level 1 and Level 2 Trauma Centers. PATIENTS/PARTICIPANTS: Fifty-three patients who underwent operative repair of midshaft clavicle fracture. INTERVENTION: All clavicles were treated by operative open reduction internal fixation. MAIN OUTCOME MEASUREMENTS: All clavicles were categorized by the Robinson classification based on injury plain film bilateral upright clavicle radiographs. In addition, intraoperative fracture characteristics of fragment length and location were measured and recorded to evaluate the fracture pattern. All fractures were analyzed to determine the frequency of segmental comminution versus length-stable patterns, analyze characteristics of butterfly fragment size, number and location as well as the location of the cortical read for those length-stable fractures. RESULTS: Analysis revealed 55% were Robinson 2B2 based on preoperative radiographs. Length-stable, anatomic reduction was achievable in 83%. For those in which an anatomic cortical read was achievable, 97.7% had a read present in the posterior-superior aspect of the clavicle. CONCLUSIONS: Midshaft clavicle fractures that meet conventional criteria for operative repair occur in a predictable manner with butterfly fragments generated from anterior-inferior compression and simple fracture line generated from tension along the posterior-superior aspect of the clavicle. Understanding this pattern can assist in the in surgical planning.

SUMOylation Regulates Transcription by the Progesterone Receptor A Isoform in a Target Gene Selective Manner.

Luminal breast cancers express estrogen (ER) and progesterone (PR) receptors, and respond to endocrine therapies. However, some ER+PR+ tumors display intrinsic or acquired resistance, possibly related to PR. Two PR isoforms, PR-A and PR-B, regulate distinct gene subsets that may differentially influence tumor fate. A high PR-A:PR-B ratio is associated with poor prognosis and tamoxifen resistance. We speculate that excessive PR-A marks tumors that will relapse early. Here we address mechanisms by which PR-A regulate transcription, focusing on SUMOylation. We use receptor mutants and synthetic promoter/reporters to show that SUMOylation deficiency or the deSUMOylase SENP1 enhance transcription by PR-A, independent of the receptors' dimerization interface or DNA binding domain. De-SUMOylation exposes the agonist properties of the antiprogestin RU486. Thus, on synthetic promoters, SUMOylation functions as an independent brake on transcription by PR-A. What about PR-A SUMOylation of endogenous human breast cancer genes? To study these, we used gene expression profiling. Surprisingly, PR-A SUMOylation influences progestin target genes differentially, with some upregulated, others down-regulated, and others unaffected. Hormone-independent gene regulation is also PR-A SUMOylation dependent. Several SUMOylated genes were analyzed in clinical breast cancer database. In sum, we show that SUMOylation does not simply repress PR-A. Rather it regulates PR-A activity in a target selective manner including genes associated with poor prognosis, shortened survival, and metastasis.

Vascular endothelial growth factor secreted by activated stroma enhances angiogenesis and hormone-independent growth of estrogen receptor-positive breast cancer.

"Reactive" or activated stroma characterizes many malignancies including breast cancers. Recently, we isolated a reactive mouse mammary gland stromal cell line called BJ3Z. These cells express alpha-smooth muscle actin and stromal cell-derived factor 1 (SDF-1) and are tumorigenic when injected into mice. Here we show that, in vivo, BJ3Z cells influence the angiogenesis and proliferation of xenografted estrogen receptor (ER)-positive MCF-7 human breast cancer cell-derived solid tumors. The growth-promoting effects of BJ3Z cells are equivalent to those of estradiol (E(2)). BJ3Z cells also increase the proliferation of normal mouse mammary luminal cells adjacent to tumors. In vitro, BJ3Z cells reorganize and increase the proliferation of cocultured malignant MCF-7 and normal human breast MCF10A cells grown as organoids in three-dimensional culture. The effects of BJ3Z cells on MCF-7 cells are equivalent to those of E(2). In contrast, BJ3Z cells do not alter the growth of highly aggressive ER-negative MDA-MB-231 human breast cancer cells. We show that BJ3Z cells secrete vascular endothelial growth factor (VEGF). The growth of MCF-7 organoids induced by BJ3Z can be inhibited by antagonists of VEGF and SDF-1. Conversely, recombinant VEGF stimulates the proliferation of MCF-7, but not MDA-MB-231, organoids. We conclude that, in addition to angiogenesis, VEGF released by activated stroma increases the growth of ER-positive malignant epithelial cells and of adjacent normal epithelium. Because activated stroma can substitute for E(2) and fosters hormone-independent growth of ER-positive tumors, we suggest that breast cancers exhibiting intrinsic hormone resistance may respond to antiangiogenic therapies.

Mechanisms underlying the control of progesterone receptor transcriptional activity by SUMOylation.

Posttranslational modification by small ubiquitin-like modifier (SUMO) is a major regulator of transcription. We previously showed that progesterone receptors (PR) have a single consensus psiKXE SUMO-conjugation motif centered at Lys-388 in the N-terminal domain of PR-B and a homologous site of PR-A. SUMOylation of the PR is hormone-dependent and has a suppressive effect on transcription of an exogenous promoter. Here we show that repression of PR activity by SUMOylation at Lys-388 is uncoupled from phosphorylation, involves synergy between tandem progesterone response elements, and is associated with lowered ligand sensitivity and slowed ligand-dependent down-regulation. However, paradoxically, cellular overexpression of SUMO-1 increases PR transcriptional activity even if Lys-388 is mutated, suggesting that the receptors are activated indirectly by other SUMOylated proteins. One of these is the coactivator SRC-1, whose binding to PR and enhancement of agonist-dependent N-/C-terminal interactions is augmented by the presence of SUMO-1. Increased transcription due to SRC-1 is independent of PR SUMOylation based on assays with the Lys-388 mutants and the pure antiprogestin ZK98299, which blocks N-/C-terminal interactions. In summary, SUMOylation tightly regulates the transcriptional activity of PR by repressing the receptors directly while activating them indirectly through augmented SRC-1 coactivation.