Correction: BAG3 promotes tumour cell proliferation by regulating EGFR signal transduction pathways in triple negative breast cancer.

[This corrects the article DOI: 10.18632/oncotarget.24590.].

BAG3 promotes tumour cell proliferation by regulating EGFR signal transduction pathways in triple negative breast cancer.

Triple-negative breast cancer (TNBC), is a heterogeneous disease characterised by absence of expression of the estrogen receptor (ER), progesterone receptor (PR) and lack of amplification of human epidermal growth factor receptor 2 (HER2). TNBC patients can exhibit poor prognosis and high recurrence stages despite early response to chemotherapy treatment. In this study, we identified a pro-survival signalling protein BCL2- associated athanogene 3 (BAG3) to be highly expressed in a subset of TNBC cell lines and tumour tissues. High mRNA expression of BAG3 in TNBC patient cohorts significantly associated with a lower recurrence free survival. The epidermal growth factor receptor (EGFR) is amplified in TNBC and EGFR signalling dynamics impinge on cancer cell survival and disease recurrence. We found a correlation between BAG3 and EGFR expression in TNBC cell lines and determined that BAG3 can regulate tumour cell proliferation, migration and invasion in EGFR expressing TNBC cells lines. We identified an interaction between BAG3 and components of the EGFR signalling networks using mass spectrometry. Furthermore, BAG3 contributed to regulation of proliferation in TNBC cell lines by reducing the activation of components of the PI3K/AKT and FAK/Src signalling subnetworks. Finally, we found that combined targeting of BAG3 and EGFR was more effective than inhibition of EGFR with Cetuximab alone in TNBC cell lines. This study demonstrates a role for BAG3 in regulation of distinct EGFR modules and highlights the potential of BAG3 as a therapeutic target in TNBC.

Treatment delay and the risk of relapse in pediatric acute lymphoblastic leukemia.

Delays or interruptions in chemotherapy due to toxicity such as neutropenia or severe infections are common in the treatment of pediatric acute lymphoblastic leukemia (ALL). Based on the reports of worse outcomes in children with poorer compliance with therapy, there has been concern that toxicity-induced therapy interruptions could also compromise treatment outcome. In a retrospective study of treatment delays in our hospital between 2003 and 2013, the case notes of 141 patients were reviewed. The cumulative lengths of delays during the whole length of chemotherapy, during the intensive phase of treatment, and during maintenance treatment were analyzed. Within these categories, delays were split between less and more than the median value. The risk of relapse did not differ between patients with a longer or shorter delay during the total length of treatment or during the intensive phase. In addition, there was a trend when comparing patients above vs below the mean in length of treatment delays during maintenance, and there was a statistically significant difference in relapses when comparing patients in the lowest and highest quartiles of maintenance delays, with fewer relapses among those patients in the highest quartile for treatment delays.

A peculiar case of the abscopal effect: radioactive iodine therapy incidentally palliating marginal zone lymphoma.

The abscopal effect is an extremely rare phenomenon occurring when irradiation or treatment of a primary tumor burden not only results in debulking of the targeted site but also reduces tumor size at distant sites from the intended treatment area. We present the abscopal effect occurring in a patient with low-grade marginal zone lymphoma who subsequently received radioactive iodine therapy for papillary thyroid carcinoma. She was 67 years old when a routine complete blood count at her primary care physician's office yielded a persistent leukocytosis of 14,500/µL with lymphocytosis of 9,870/µL. Immunophenotyping and fluorescence in situ hybridization (FISH) analysis confirmed low-grade marginal zone lymphoma. Over eight years, her peak leukocyte and lymphocyte counts were 24,100/µL and 18,100/µL, respectively. Subsequently, she was diagnosed with papillary thyroid carcinoma after presenting with a new complaint of dysphagia. A total thyroidectomy was performed, followed by 172.1 millicuries of oral I-131 sodium iodine radioactive ablation therapy. Following treatment, her leukocyte and lymphocyte counts were 3,100/µL and 1,100/µL, respectively. Over the next four years, her leukocyte and lymphocyte counts remained within normal limits and she remained symptom free. To our knowledge, there has never been a published report describing the use of radioactive iodine causing abscopal effect benefits for patients with underlying lymphoproliferative diseases.

Proteomic analysis reveals a role for Bcl2-associated athanogene 3 and major vault protein in resistance to apoptosis in senescent cells by regulating ERK1/2 activation.

Senescence is a prominent solid tumor response to therapy in which cells avoid apoptosis and instead enter into prolonged cell cycle arrest. We applied a quantitative proteomics screen to identify signals that lead to therapy-induced senescence and discovered that Bcl2-associated athanogene 3 (Bag3) is up-regulated after adriamycin treatment in MCF7 cells. Bag3 is a member of the BAG family of co-chaperones that interacts with Hsp70. Bag3 also regulates major cell-signaling pathways. Mass spectrometry analysis of the Bag3 Complex revealed a novel interaction between Bag3 and Major Vault Protein (MVP). Silencing of Bag3 or MVP shifts the cellular response to adriamycin to favor apoptosis. We demonstrate that Bag3 and MVP contribute to apoptosis resistance in therapy-induced senescence by increasing the level of activation of extracellular signal-regulated kinase1/2 (ERK1/2). Silencing of either Bag3 or MVP decreased ERK1/2 activation and promoted apoptosis in adriamycin-treated cells. An increase in nuclear accumulation of MVP is observed during therapy-induced senescence and the shift in MVP subcellular localization is Bag3-dependent. We propose a model in which Bag3 binds to MVP and facilitates MVP accumulation in the nucleus, which sustains ERK1/2 activation. We confirmed that silencing of Bag3 or MVP shifts the response toward apoptosis and regulates ERK1/2 activation in a panel of diverse breast cancer cell lines. This study highlights Bag3-MVP as an important complex that regulates a potent prosurvival signaling pathway and contributes to chemotherapy resistance in breast cancer.

Enhanced intrinsic migration of aggressive breast cancer cells by inhibition of Rac1 GTPase.

Rac GTPases are known to play a crucial role in regulating cytoskeletal changes necessary for cell migration. Migration has been shown to be positively regulated by Rac in most cell types. However, there is also a large body of conflicting evidence in some other cell types with respect to the role of Rac in migration, suggesting that Rac GTPases regulate cell migration in a cell type-dependent manner. In the present study, we have characterized the effects of Rac1 GTPase inhibition on the migratory abilities of a number of breast cancer cell lines with differential degrees of tumorigenic and metastatic potentials. We show that Rac1 inhibition in non-metastatic (MCF-7, T-47D) or moderately metastatic (Hs578T) cell lines results in inhibition of migration, whereas in highly metastatic cell lines (MDA-MB-435, MDA-MB-231, and C3L5) Rac1 inhibition results in stimulation of migration. This stimulation of migration following Rac1 inhibition is also accompanied by the enhanced RhoA activity, suggesting a possible existence of a dominating role of RhoA over Rac1 in regulating intrinsic migration of the highly metastatic breast cancer cells.