Combined Dusp4 and p53 loss with Dbf4 amplification drives tumorigenesis via cell cycle restriction and replication stress escape in breast cancer.

AIM: Deregulated signaling pathways are a hallmark feature of oncogenesis and driver of tumor progression. Dual specificity protein phosphatase 4 (DUSP4) is a critical negative regulator of the mitogen-activated protein kinase (MAPK) pathway and is often deleted or epigenetically silenced in tumors. DUSP4 alterations lead to hyperactivation of MAPK signaling in many cancers, including breast cancer, which often harbor mutations in cell cycle checkpoint genes, particularly in TP53. METHODS: Using a genetically engineered mouse model, we generated mammary-specific Dusp4-deleted primary epithelial cells to investigate the necessary conditions in which DUSP4 loss may drive breast cancer oncogenesis. RESULTS: We found that Dusp4 loss alone is insufficient in mediating tumorigenesis, but alternatively converges with loss in Trp53 and MYC amplification to induce tumorigenesis primarily through chromosome 5 amplification, which specifically upregulates Dbf4, a cell cycle gene that promotes cellular replication by mediating cell cycle checkpoint escape. CONCLUSIONS: This study identifies a novel mechanism for breast tumorigenesis implicating Dusp4 loss and p53 mutations in cellular acquisition of Dbf4 upregulation as a driver of cellular replication and cell cycle checkpoint escape.

Pembrolizumab plus cetuximab in patients with recurrent or metastatic head and neck squamous cell carcinoma: an open-label, multi-arm, non-randomised, multicentre, phase 2 trial.

BACKGROUND: Pembrolizumab (PD-1 inhibitor) and cetuximab (EGFR inhibitor) are active as single agents and in combination with cytotoxic chemotherapy for recurrent or metastatic head and neck squamous cell carcinoma (HNSCC). Given each drug's single agent activity and unique mechanism of action, we aimed to evaluate the anti-tumour activity of PD-1 blockade with EGFR inhibition in recurrent or metastatic HNSCC. METHODS: This study is an open-label, non-randomised, multi-arm, phase 2 trial done at four academic centres in the USA. Participants were required to have platinum-resistant or platinum-ineligible, recurrent or metastatic HNSCC, be at least 18 years old, have an Eastern Cooperative Oncology Group performance status 0-1, have measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, and to have received no previous immunotherapy or EGFR inhibition. All participants received pembrolizumab 200 mg intravenously every 3 weeks, combined with an initial loading dose of cetuximab 400 mg/m2 intravenously followed by 250 mg/m2 intravenously weekly (21 day cycle). The primary endpoint was overall response rate defined as the proportion of participants with a partial or complete responses (per RECIST version 1.1) by 6 months in the intention-to-treat population. The safety population included all participants who received at least one dose of pembrolizumab. Herein, the final analysis of cohort 1 (no previous PD-1, PD-L1, or EGFR inhibition for recurrent or metastatic HNSCC) is reported. Three additional cohorts (two for participants with a previous response to immunotherapy followed by relapse or progression, with or without previous cetuximab exposure, and one for cutaneous HNSCC) will be reported separately once fully accrued. This study is registered with ClinicalTrials.gov, NCT03082534, and remains open as the three additional cohorts are actively accruing participants. FINDINGS: Between March 22, 2017, and July 16, 2019, 33 participants were enrolled to cohort 1. All 33 participants received at least one dose of pembrolizumab. Median follow-up duration was 7·3 months (IQR 3·9-10·9). By 6 months, the overall response rate was 45% (95% CI 28-62), with 15 of 33 participants achieving a partial response. The most common grade 3-4 treatment-related adverse event was oral mucositis (three [9%] of 33 participants), and serious treatment-related adverse events occurred in five (15%) participants. No treatment-related deaths occurred. INTERPRETATION: Pembrolizumab combined with cetuximab shows promising clinical activity for recurrent or metastatic HNSCC, and merits further investigation. FUNDING: Merck Sharp & Dohme.

PIK3CA and MAP3K1 alterations imply luminal A status and are associated with clinical benefit from pan-PI3K inhibitor buparlisib and letrozole in ER+ metastatic breast cancer.

Clinical trials have demonstrated the efficacy of combining phosphoinositide 3-kinase (PI3K) inhibitors with endocrine therapies in hormone therapy-refractory breast cancer. However, biomarkers of PI3K pathway dependence in ER+ breast cancer have not been fully established. Hotspot mutations in the alpha isoform of PI3K (PIK3CA) are frequent in ER+ disease and may identify tumors that respond to PI3K inhibitors. It is unclear whether PIK3CA mutations are the only biomarker to suggest pathway dependence and response to therapy. We performed correlative molecular characterization of primary and metastatic tissue from patients enrolled in a phase Ib study combining buparlisib (NVP-BKM-120), a pan-PI3K inhibitor, with letrozole in ER+, human epidermal growth factor-2 (HER2)-negative, metastatic breast cancer. Activating mutations in PIK3CA and inactivating MAP3K1 mutations marked tumors from patients with clinical benefit (≥6 months of stable disease). Patients harboring mutations in both genes exhibited the greatest likelihood of clinical benefit. In ER+ breast cancer cell lines, siRNA-mediated knockdown of MAP3K1 did not affect the response to buparlisib. In a subset of patients treated with buparlisib or the PI3Kα inhibitor alpelisib each with letrozole where PAM50 analysis was performed, nearly all tumors from patients with clinical benefit had a luminal A subtype. Mutations in MAP3K1 in ER+ breast cancer may be associated with clinical benefit from combined inhibition of PI3K and ER, but we could not ascribe direct biological function therein, suggesting they may be a surrogate for luminal A status. We posit that luminal A tumors may be a target population for this therapeutic combination.

USP11 Enhances TGFß-Induced Epithelial-Mesenchymal Plasticity and Human Breast Cancer Metastasis.

Epithelial-mesenchymal transition (EMT) is a conserved cellular plasticity program that is reactivated in carcinoma cells and drives metastasis. Although EMT is well studied its regulatory mechanisms remain unclear. Therefore, to identify novel regulators of EMT, a data mining approach was taken using published microarray data and a group of deubiquitinases (DUB) were found to be upregulated in cells that have undergone EMT. Here, it is demonstrated that one DUB, ubiquitin-specific peptidase 11 (USP11), enhances TGFß-induced EMT and self-renewal in immortalized human mammary epithelial cells. Furthermore, modulating USP11 expression in human breast cancer cells altered the migratory capacity in vitro and metastasis in vivo Moreover, elevated USP11 expression in human breast cancer patient clinical specimens correlated with decreased survival. Mechanistically, modulating USP11 expression altered the stability of TGFß receptor type II (TGFBR2) and TGFß downstream signaling in human breast cancer cells. Together, these data suggest that deubiquitination of TGFBR2 by USP11 effectively spares TGFBR2 from proteasomal degradation to promote EMT and metastasis.Implications: USP11 regulates TGFß-induced epithelial-mesenchymal plasticity and human breast cancer metastasis and may be a potential therapeutic target for breast cancer. Mol Cancer Res; 16(7); 1172-84. ©2018 AACR.