The Role of Smoothened in Mammary Gland Development and Breast Cancer

The hedgehog (Hh) signaling pathway is a critical pathway for development and is known to influence proliferation, cell fate, morphogenesis, and stem cell self-renewal. Mutations activating Hh signaling have been found in a wide variety of cancers, and it is estimated that up to 25% of all tumors display misregulated Hh signaling. Smoothened (Smo), a seven pass transmembrane protein is the Hh signaling pathway's primary effector and its sole non-redundant member. In a recent study, Smo was found to be over-expressed in 70% of ductal carcinom in-situ (DCIS) lesions and 30% of invasive breast carcinomas (IBC). Despite the implication of this protein in breast cancer, little is known about its role in normal mammary gland development.In order to understand the role of Smo in mammary gland development we have performed phenotypic analyses of a conditional mouse model expressing constitutively activated Smo under the control of a mammary gland selective Cre recombinase. We show that activation of the Hh pathway results in increased proliferation starting around five weeks of age that leads to a dramatic increase in branching and budding of the mammary gland at around ten weeks of age. In addition, immunostaining using the ductal markers Na-K-Cl Co-transporter 1 (NKCC1) and aquaporin 5 (AQP5) suggests alterations in cell fate. Finally, these mice exhibit changes in the stroma surrounding the mammary ducts including an increase in collagen deposition. Gene profiling studies show upregulation of several genes, including targets of the Notch pathway, in ten-week-old virgin mammary glands from the constitutively active conditional Smo mouse model when compared to control. Surprisingly, canonical downstream Hh target genes like Patched and Gli were not found to be upregulated. These data in conjunction with recent published studies suggest that Smo activation in the mammary gland may be acting via a non-canonical mechanism to produce the observed hyper-branched and budded phenotype. Preliminary studies indicate that Smoothened may be functioning as a G-protein coupled receptor (GPCR) via a pertussis-toxin sensitive mechanism. Interestingly, constituitive Smo activity does not appear to alter cyclic AMP (cAMP) levels as recently reported in Drosophila indicating that mammalian Smo may be acting via a different mechanism.In addition to these gain-of-function studies, experiments are underway utilizing a conditional null Smo mouse model (loss-of-function) to determine if there is a requirement for Hh pathway activation in normal mammary gland development. Preliminary analysis indicates that partial loss of Smo in mammary gland cells leads to impaired ductal elongation and reduced branching.Future studies will include the generation of mammary gland chimeras to study the possible paracrine interactions between Smo over-expressing and wild type cells. Additionally, experiments are under way to elucidate the mechanism of Smo's GPCR function in the mammary gland.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2164.

Adjuvant sunitinib following chemoradiotherapy (CRT) and surgery for esophageal cancer: A phase II trial

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Background: Locally advanced esophageal cancer (LAEC) has a 5-year survival of < 30 %. Most patients (pts) fail after curative intent tri-modality treatment with distant metastatic disease. This phase II trial aims to determine if adjuvant targeted therapy, after neoadjuvant CRT plus surgery for resectable LAEC, may impact on systemic disease without significant toxicity. Methods: Pts with LAEC of the thoracic esophagus or gastroesophageal junction, ECOG PS 0,1 and surgical candidates treated with: preoperative Irinotecan (65mg/m2 initially, ammended to 50mg/m2) + Cisplatin (30mg/m2) on weeks 1,2,4,5,7,8 + concurrent conformal radiotherapy (50Gy/25 fractions) on weeks 4–8. Esophagectomy during weeks 15–18. Sunitinib 37.5mg daily (escalating to 50mg daily if tolerated) commenced 4–12 weeks post surgery, for 1 year. Primary endpoint is feasibility and efficacy of adjuvant sunitinib. Planned sample size 36pts. Results: 30pts enrolled from 11/06 to 12/08. Median age 64 yr (43–71), male: 22, adenocarcinoma: squamous 22:6; 10 pts stage IIA, 5 IIB and 13 III. 2 pts excluded with positive PET scan. 28 pts completed CRT - 18 pts (64%) received ≥80% of planned chemotherapy dose, 23 pts (82%) received full radiation dose. Grade 3/4 toxicity included: neutropenia (17/28), diarrhea (7/28), dehydration (4/28), febrile neutropenia (FN) (3/28) and nausea (2/28). 2 deaths on chemotherapy (1 bacterial meningitis, 1 FN) leading to irinotecan dose- reduction. Dysphagia improved in 14/23 pts during CRT. 18 pts have undergone esophagectomy. Complete pathological response in 4 (22%), downstaging in 3 (17%), stable disease in 11 (61%). 2 pts unresectable (metastases at laparotomy). 1 post-operative death due to pulmonary embolus. 9 pts have commenced sunitinib, 6 maintained at starting dose of 37.5mg; 2 dose reductions; 1 discontinued with poor wound healing. Grade 3 toxicity included: leukopenia (2/9), hand-foot reaction (1/9) and depression (1/9). Conclusions: In LAEC, induction Irinotecan/Cisplatin and radiotherapy followed by esophagectomy is associated with a significant but manageable toxicity profile. Early initiation of sunitinib is feasible and well-tolerated. Updated results to be presented.

No significant financial relationships to disclose.

Impact of induction chemotherapy and adjuvant radiation therapy on outcome after extrapleural pneumonectomy for malignant pleural mesothelioma

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Background: Examine the results of tri-modality therapy for malignant pleural mesothelioma (MPM). Methods: Protocol consisted of induction cisplatin-based chemotherapy, followed by extrapleural pneumonectomy (EPP) and adjuvant hemithoracic radiation therapy (RT) to 54 Gy. Results: A total of 60 patients were suitable candidates for tri-modality therapy between 01/2001 and 01/2007. Induction chemotherapy was administered to 56 patients; 4 patients underwent EPP without induction chemotherapy because of patient refusal (n=2), previous chemotherapy (n=1) and sarcomatoid MPM (n=1). Chemotherapy included vinorelbine/cisplatin (n=26), pemetrexed/cisplatin (n=26) and gemcitabine/cisplatin (n=4). EPP was performed in 47 patients; 13 patients did not undergo EPP because of tumor progression during chemotherapy (n=2), extensive chest wall involvement at surgery (n=6), or involvement of mediastinal lymph nodes at mediastinoscopy (n=5). Three patients (6%) died within 30 days of surgery. Pathological stage was II (n=6), III (n=35), and IV (n=6). Adjuvant RT was administered postoperatively to 36 patients and is ongoing in 5 patients; 6 patients did not receive adjuvant RT because of fatigue (n=5) or previous RT (n=1), and 4 patients did not complete RT up to 54 Gy. Overall survival for the 23 patients who completed the tri-modality therapy was 37% at 3 years with a median survival of 15 months. Eleven of the 23 patients had recurrence after a median of 8 months (range, 2–13 months). Recurrences were locoregional (n=2), in contralateral chest (n=3), abdomen (n=3), contralateral chest and abdomen (n=2), or pericardium (n=1). Among patients undergoing EPP, disease-free survival was longer in patients undergoing adjuvant high dose hemithoracic RT (p=0.07), in epithelial tumors (p=0.03), and in early stage (p=0.07). Overall survival was influenced by histology (p=0.007) and stage (p=0.05), but not by adjuvant high dose hemithoracic RT (p=0.5). The type of chemotherapy had no impact on disease-free and overall survival. Conclusions: Aggressive tri-modality therapy is feasible in selected patient with MPM. Adjuvant high dose hemithoracic RT can improve disease free survival and achieve good local control.

No significant financial relationships to disclose.