Inhibition of a new AXL isoform, AXL3, induces apoptosis of mantle cell lymphoma cells.

Mantle cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin lymphoma having a poor overall survival that is in need for the development of new therapeutics. In this study, we report the identification and expression of a new isoform splice variant of the tyrosine kinase receptor AXL in MCL cells. This new AXL isoform, called AXL3, lacks the ligand-binding domain of the commonly described AXL splice variants and is constitutively activated in MCL cells. Interestingly, functional characterization of AXL3, using CRISPR inhibition, revealed that only the knock down of this isoform leads to apoptosis of MCL cells. Importantly, pharmacological inhibition of AXL activity resulted in a significant decrease in the activation of well-known proproliferative and survival pathways activated in MCL cells (ie, ß-catenin, Ak strain transforming, and NF-κB). Therapeutically, preclinical studies using a xenograft mouse model of MCL indicated that bemcentinib is more effective than ibrutinib in reducing the tumor burden and to increase the overall survival. Our study highlights the importance of a previously unidentified AXL splice variant in cancer and the potential of bemcentinib as a targeted therapy for MCL.

Dihydroorotate dehydrogenase inhibition acts synergistically with tyrosine kinase inhibitors to induce apoptosis of mantle cell lymphoma cells.

Mantle cell lymphoma (MCL) is a non-Hodgkin lymphoma that remains incurable with the treatment options available today. In the present study, we have identified the dihydroorotate dehydrogenase (DHODH), an essential enzyme for the de novo biosynthesis of pyrimidine-based nucleotides, to be overexpressed in MCL in comparison to healthy peripheral blood mononuclear cells (PBMC). In vitro inhibition of the DHODH activity using a newly developed DHODH inhibitor, namely (R)-HZ05, can induce MCL cell death in the nanomolar range independently than the P53 status of the investigated cell lines. Moreover, the combination of (R)-HZ05 with tyrosine kinase inhibitor shows the synergistic activity on cell death. Pre-clinical investigation on the efficacy of (R)-HZ05 shows that it can be prolonged animal lifespan similar to ibrutinib. (R)-HZ05 use in combination with tyrosine kinase inhibitor demonstrated a superior efficacy on tumor burden reduction and survival than either drug alone. We have demonstrated that the depletion of the pyrimidine nucleotide pool, using DHODH inhibitor, represents a new therapeutic strategy that may benefit MCL patients.

"Talk to me, not at me": obese women's experiences of birth and their encounter with birth attendants-a qualitative study.

Purpose: To explore the birth experiences of obese women in regard to their encounter with birth attendants. Methods: Qualitative, in-depth interviews with 10 women were conducted in February 2020. Data were analysed using a descriptive phenomenological method. Results: Four interrelated constituents were identified: The preconception and prejudice of being unhealthy and less able; Being unique among all the other unique women; "Talk to me, not at me"-the importance of information and communication, and; Feeling secure enough to be in the 'birthing bubble'. Conclusion: For the women in our study, being obese meant experiencing challenges as well as opportunities during childbirth and in their encounter with birth attendants. Experiences of preconceptions, alienation, a focus on risk and a loss of autonomy in encounters with birth attendants were found to negatively impact the birthing process. The women desired affirmative and inclusive encounters; these kinds of encounters may improve the birth experiences of obese women.

CD24-targeted fluorescence imaging in patient-derived xenograft models of high-grade serous ovarian carcinoma.

BACKGROUND: The survival rate of patients with advanced high-grade serous ovarian carcinoma (HGSOC) remains disappointing. Clinically translatable orthotopic cell line xenograft models and patient-derived xenografts (PDXs) may aid the implementation of more personalised treatment approaches. Although orthotopic PDX reflecting heterogeneous molecular subtypes are considered the most relevant preclinical models, their use in therapeutic development is limited by lack of appropriate imaging modalities. METHODS: We developed novel orthotopic xenograft and PDX models for HGSOC, and applied a near-infrared fluorescently labelled monoclonal antibody targeting the cell surface antigen CD24 for non-invasive molecular imaging of epithelial ovarian cancer. CD24-Alexa Fluor 680 fluorescence imaging was compared to bioluminescence imaging in three orthotopic cell line xenograft models of ovarian cancer (OV-90luc+, Skov-3luc+ and Caov-3luc+, n = 3 per model). The application of fluorescence imaging to assess treatment efficacy was performed in carboplatin-paclitaxel treated orthotopic OV-90 xenografts (n = 10), before the probe was evaluated to detect disease progression in heterogenous PDX models (n = 7). FINDINGS: Application of the near-infrared probe, CD24-AF680, enabled both spatio-temporal visualisation of tumour development, and longitudinal therapy monitoring of orthotopic xenografts. Notably, CD24-AF680 facilitated imaging of multiple PDX models representing different histological subtypes of the disease. INTERPRETATION: The combined implementation of CD24-AF680 and orthotopic PDX models creates a state-of-the-art preclinical platform which will impact the identification and validation of new targeted therapies, fluorescence image-guided surgery, and ultimately the outcome for HGSOC patients. FUNDING: This study was supported by the H2020 program MSCA-ITN [675743], Helse Vest RHF, and Helse Bergen HF [911809, 911852, 912171, 240222, HV1269], as well as by The Norwegian Cancer Society [182735], and The Research Council of Norway through its Centers of excellence funding scheme [223250, 262652].

Preclinical Evaluation of the Pan-FGFR Inhibitor LY2874455 in FRS2-Amplified Liposarcoma.

Background: FGFR inhibition has been proposed as treatment for dedifferentiated liposarcoma (DDLPS) with amplified FRS2, but we previously only demonstrated transient cytostatic effects when treating FRS2-amplified DDLPS cells with NVP-BGJ398. Methods: Effects of the more potent FGFR inhibitor LY2874455 were investigated in three DDLPS cell lines by measuring effects on cell growth and apoptosis in vitro and also testing efficacy in vivo. Genome, transcriptome and protein analyses were performed to characterize the signaling components in the FGFR pathway. Results: LY2874455 induced a stronger, longer-lasting growth inhibitory effect and moderate level of apoptosis for two cell lines. The third cell line, did not respond to FGFR inhibition, suggesting that FRS2 amplification alone is not sufficient to predict response. Importantly, efficacy of LY2874455 was confirmed in vivo, using an independent FRS2-amplified DDLPS xenograft model. Expression of FRS2 was similar in the responding and non-responding cell lines and we could not find any major difference in downstream FGFR signaling. The only FGF expressed by unstimulated non-responding cells was the intracellular ligand FGF11, whereas the responding cell lines expressed extracellular ligand FGF2. Conclusion: Our study supports LY2874455 as a better therapy than NVP-BGJ398 for FRS2-amplified liposarcoma, and a clinical trial is warranted.

GRP94 rewires and buffers the FLT3-ITD signaling network and promotes survival of acute myeloid leukemic stem cells.

Internal tandem duplications in the tyrosine kinase receptor FLT3 (FLT3-ITD) are among the most common lesions in acute myeloid leukemia and there exists a need for new forms of treatment. Using ex vivo drug sensitivity screening, we found that FLT3-ITD+ patient cells are particularly sensitive to HSP90 inhibitors. While it is well known that HSP90 is important for FLT3-ITD stability, we found that HSP90 family members play a much more complex role in FLT3-ITD signaling than previously appreciated. First, we found that FLT3-ITD activates the unfolded protein response, leading to increased expression of GRP94/HSP90B1. This results in activation of a nefarious feedback loop, in which GRP94 rewires FLT3-ITD signaling by binding and retaining FLT3-ITD in the endoplasmic reticulum, leading to aberrant activation of downstream signaling pathways and further inducing the unfolded protein response. Second, HSP90 family proteins protect FLT3-ITD+ acute myeloid leukemia cells against apoptosis by alleviating proteotoxic stress, and treatment with HSP90 inhibitors results in proteotoxic overload that triggers unfolded protein response-induced apoptosis. Importantly, leukemic stem cells are strongly dependent upon HSP90 for their survival, and the HSP90 inhibitor ganetespib causes leukemic stem cell exhaustion in patient-derived mouse xenograft models. Taken together, our study reveals a molecular basis for HSP90 addiction of FLT3-ITD+ acute myeloid leukemia cells and provides a rationale for including HSP90 inhibitors in the treatment regime for FLT3-ITD+ acute myeloid leukemia.