Mesenchymal Stem Cell Transition to Tumor-Associated Fibroblasts Contributes to Fibrovascular Network Expansion and Tumor Progression

Tumor associated fibroblasts (TAF), are essential for tumor progression providing both a functional and structural supportive environment. TAF, known as activated fibroblasts, have an established biological impact on tumorigenesis as matrix synthesizing or matrix degrading cells, contractile cells, and even blood vessel associated cells. The production of growth factors, cytokines, chemokines, matrix-degrading enzymes, and immunomodulatory mechanisms by these cells augment tumor progression by providing a suitable environment. There are several suggested origins of the TAF including tissue-resident, circulating, and epithelial-to-mesenchymal-transitioned cells.We provide evidence that TAF are derived from mesenchymal stem cells (MSC) that acquire a TAF phenotype following exposure to or systemic recruitment into adenocarcinoma xenograft models including breast, pancreatic, and ovarian. We define the MSC derived TAF in a xenograft ovarian carcinoma model by the immunohistochemical presence of 1) fibroblast specific protein and fibroblast activated protein; 2) markers phenotypically associated with aggressiveness, including tenascin-c, thrombospondin-1, and stromelysin-1; 3) production of pro-tumorigenic growth factors including hepatocyte growth factor, epidermal growth factor, and interleukin-6; and 4) factors indicative of vascularization, including alpha-smooth muscle actin, desmin, and vascular endothelial growth factor. We demonstrate that under long-term tumor conditioning in vitro, MSC express TAF-like proteins. Additionally, human MSC but not murine MSC stimulated tumor growth primarily through the paracrine production of secreted IL6.Our results suggest the dependence of in vitro Skov-3 tumor cell proliferation is due to the presence of tumor-stimulated MSC secreted IL6. The subsequent TAF phenotype arises from the MSC which ultimately promotes tumor growth through the contribution of microvascularization, stromal networks, and the production of tumor-stimulating paracrine factors

STAT3 can be activated through paracrine signaling in breast epithelial cells

<p>Abstract</p> <p>Background</p> <p>Many cancers, including breast cancer, have been identified with increased levels of phosphorylated or the active form of Signal Transducers and Activators of Transcription 3 (STAT3) protein. However, whether the tumor microenvironment plays a role in this activation is still poorly understood.</p> <p>Methods</p> <p>Conditioned media, which contains soluble factors from MDA-MB-231 and MDA-MB-468 breast cancer cells and breast cancer associated fibroblasts, was added to MCF-10A breast epithelial and MDA-MB-453 breast cancer cells. The stimulation of phosphorylated STAT3 (p-STAT3) levels by conditioned media was assayed by Western blot in the presence or absence of neutralized IL-6 antibody, or a JAK/STAT3 inhibitor, JSI-124. The stimulation of cell proliferation in MCF-10A cells by conditioned media in the presence or absence of JSI-124 was subjected to MTT analysis. IL-6, IL-10, and VEGF levels were determined by ELISA analysis.</p> <p>Results</p> <p>Our results demonstrated that conditioned media from cell lines with constitutively active STAT3 are sufficient to induce p-STAT3 levels in various recipients that do not possess elevated p-STAT3 levels. This signaling occurs through the JAK/STAT3 pathway, leading to STAT3 phosphorylation as early as 30 minutes and is persistent for at least 24 hours. ELISA analysis confirmed a correlation between elevated levels of IL-6 production and p-STAT3. Neutralization of the IL-6 ligand or gp130 was sufficient to block increased levels of p-STAT3 (Y705) in treated cells. Furthermore, soluble factors within the MDA-MB-231 conditioned media were also sufficient to stimulate an increase in IL-6 production from MCF-10A cells.</p> <p>Conclusion</p> <p>These results demonstrate STAT3 phosphorylation in breast epithelial cells can be stimulated by paracrine signaling through soluble factors from both breast cancer cells and breast cancer associated fibroblasts with elevated STAT3 phosphorylation. The induction of STAT3 phosphorylation is through the IL-6/JAK pathway and appears to be associated with cell proliferation. Understanding how IL-6 and other soluble factors may lead to STAT3 activation via the tumor microenvironment will provide new therapeutic regimens for breast carcinomas and other cancers with elevated p-STAT3 levels.</p

Deep sustained response to daratumumab monotherapy associated with T-cell expansion in triple refractory myeloma

Abstract Background Daratumumab, a human CD38 monoclonal antibody that has direct on-tumor and immunomodulatory mechanisms of action, demonstrated clinical benefit as monotherapy or in combination with established regimens in patients with multiple myeloma with one or more prior lines of therapy. Case presentation A male patient, who was 70 years of age at the time of diagnosis of multiple myeloma in 2011, relapsed after five lines of therapy, including autologous stem cell transplantation. The patient’s disease, which was considered high risk with a deletion of chromosome 17p, advanced quickly and was triple refractory 2 years after diagnosis leaving few treatment options. He was treated with daratumumab monotherapy in the SIRIUS clinical trial resulting in a stringent complete response and clearance of minimal residual disease. The duration of the patient’s clinical response is now over 3.5 years without relapse, compared with a median of 7.6 months for similarly treated patients. The patient’s immunophenotype revealed CD8+ T-cell expansion, clonal expansion of the T-cell receptor repertoire, and decreases in regulatory T cells during daratumumab therapy, suggesting a robust adaptive immune response. This immune response was still present 32 months into daratumumab therapy. Conclusions The results from this case report showed that a patient with advanced multiple myeloma, who had exhausted all treatment options with existing regimens, mounted an ongoing, deep, and durable response to daratumumab monotherapy. Further investigation of the immunologic profile provided additional patient-level evidence of an immunomodulatory mechanism of action of daratumumab. Trial registration ClinicalTrials.gov Identifier number NCT01985126. Submitted 22 July 201

Monoclonal antibodies targeting CD38 in hematological malignancies and beyond

CD38 is a multifunctional cell surface protein that has receptor as well as enzyme functions. The protein is generally expressed at low levels on various hematological and solid tissues, while plasma cells express particularly high levels of CD38. The protein is also expressed in a subset of hematological tumors, and shows especially broad and high expression levels in plasma cell tumors such as multiple myeloma (MM). Together, this triggered the development of various therapeutic CD38 antibodies, including daratumumab, isatuximab, and MOR202. Daratumumab binds a unique CD38 epitope and showed strong anti‐tumor activity in preclinical models. The antibody engages diverse mechanisms of action, including complement‐dependent cytotoxicity, antibody‐dependent cellular cytotoxicity, antibody‐dependent cellular phagocytosis, programmed cell death, modulation of enzymatic activity, and immunomodulatory activity. CD38‐targeting antibodies have a favorable toxicity profile in patients, and early clinical data show a marked activity in MM, while studies in other hematological malignancies are ongoing. Daratumumab has single agent activity and a limited toxicity profile, allowing favorable combination therapies with existing as well as emerging therapies, which are currently evaluated in the clinic. Finally, CD38 antibodies may have a role in the treatment of diseases beyond hematological malignancies, including solid tumors and antibody‐mediated autoimmune diseases

NAD⁺-Metabolizing Ectoenzymes in Remodeling Tumor-Host Interactions: The Human Myeloma Model

Nicotinamide adenine dinucleotide (NAD⁺) is an essential co-enzyme reported to operate both intra- and extracellularly. In the extracellular space, NAD⁺ can elicit signals by binding purinergic P2 receptors or it can serve as the substrate for a chain of ectoenzymes. As a substrate, it is converted to adenosine (ADO) and then taken up by the cells, where it is transformed and reincorporated into the intracellular nucleotide pool. Nucleotide-nucleoside conversion is regulated by membrane-bound ectoenzymes. CD38, the main mammalian enzyme that hydrolyzes NAD⁺, belongs to the ectoenzymatic network generating intracellular Ca(2+)-active metabolites. Within this general framework, the extracellular conversion of NAD⁺ can vary significantly according to the tissue environment or pathological conditions. Accumulating evidence suggests that tumor cells exploit such a network for migrating and homing to protected areas and, even more importantly, for evading the immune response. We report on the experience of this lab to exploit human multiple myeloma (MM), a neoplastic expansion of plasma cells, as a model to investigate these issues. MM cells express high levels of surface CD38 and grow in an environment prevalently represented by closed niches hosted in the bone marrow (BM). An original approach of this study derives from the recent use of the clinical availability of therapeutic anti-CD38 monoclonal antibodies (mAbs) in perturbing tumor viability and enzymatic functions in conditions mimicking what happens in vivo