L-DOS47 Elevates Pancreatic Cancer Tumor pH and Enhances Response to Immunotherapy.

Acidosis is an important immunosuppressive mechanism that leads to tumor growth. Therefore, we investigated the neutralization of tumor acidity to improve immunotherapy response. L-DOS47, a new targeted urease immunoconjugate designed to neutralize tumor acidity, has been well tolerated in phase I/IIa trials. L-DOS47 binds to CEACAM6, a cell-surface protein that is highly expressed in gastrointestinal cancers, allowing urease to cleave endogenous urea into two NH4+ and one CO2, thereby raising local pH. To test the synergetic effect of neutralizing tumor acidity with immunotherapy, we developed a pancreatic orthotopic murine tumor model (KPC961) expressing human CEACAM6. Using chemical exchange saturation transfer-magnetic resonance imaging (CEST-MRI) to measure the tumor extracellular pH (pHe), we confirmed that L-DOS47 raises the tumor pHe from 4 h to 96 h post injection in acidic tumors (average increase of 0.13 units). Additional studies showed that combining L-DOS47 with anti-PD1 significantly increases the efficacy of the anti-PD1 monotherapy, reducing tumor growth for up to 4 weeks.

L-DOS47 enhances response to immunotherapy in pancreatic cancer tumor.

Acidosis is an important immunosuppressive mechanism that leads to tumor growth. Therefore, we investigated the neutralization of tumor acidity to improve immunotherapy response. L-DOS47, a new targeted urease immunoconjugate designed to neutralize tumor acidity, has been well tolerated in phase I/IIa trials. L-DOS47 binds CEACAM6, a cell surface protein highly expressed in gastrointestinal cancers, allowing urease to cleave endogenous urea into two NH4+ and one CO2, thereby raising local pH. To test the synergetic effect of neutralizing tumor acidity with immunotherapy, we developed a pancreatic orthotopic murine tumor model (KPC961) expressing human CEACAM6. Our results demonstrate that combining L DOS47 with anti-PD1 significantly increases the efficacy of anti-PD1 monotherapy, reducing tumor growth for up to 4 weeks.

CellTrace™ Violet Flow Cytometric Assay to Assess Cell Proliferation.

CellTrace™ Violet (CTV) is a powerful tool for tracking cell proliferation by permanently binding cellular proteins and rendering the cell fluorescent. After cell division, each daughter cell contains half of the parent cell's fluorescence, enabling quantification of proliferation via flow cytometry. This method enables monitoring of several generations of cell division and tracking of different cell populations in co-culture. Here we describe the use of CellTrace™ Violet in different cell types, and we share important observations we made during protocol optimization.

Docosahexaenoic Acid in the Inhibition of Tumor Cell Growth in Preclinical Models of Ovarian Cancer.

There is a strong rationale for investigating nutritional interventions with docosahexaenoic acid (DHA) in cancer prevention and therapy; however, the effects of DHA on ovarian cancer (OC) have not been well studied. Here, we investigated if DHA alone and in combination with carboplatin reduces OC cell growth in vitro. In vivo, we used a high-grade serous OC patient-derived xenograft (PDX) mouse model to investigate if DHA affects OC growth and enhances the anticancer actions of carboplatin. We showed synergistic cell killing by DHA and carboplatin in DHA-resistant Kuramochi and SKOV3 OC cells, which corresponded with increased DHA incorporation into whole-cell membrane phospholipids (P < 0.05). In vivo, feeding mice a diet supplemented with 3.9% (w/w of fat) DHA resulted in a significant reduction in PDX growth with and without carboplatin (P < 0.05). This reduction in tumor growth was accompanied by an increased tumor necrotic region (P < 0.05) and improved survival. Plasma membranes in tumors and livers excised from mice fed a DHA diet had ∼ twofold increase in DHA incorporation as compared with mice fed a control diet. Our findings indicate that DHA supplementation reduces cancer cell growth and enhances the efficacy of carboplatin in preclinical models of OC through increased apoptosis and necrosis.Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.1952453.

Embryonic protein NODAL regulates the breast tumor microenvironment by reprogramming cancer-derived secretomes.

The tumor microenvironment (TME) is an important mediator of breast cancer progression. Cancer-associated fibroblasts constitute a major component of the TME and may originate from tissue-associated fibroblasts or infiltrating mesenchymal stromal cells (MSCs). The mechanisms by which cancer cells activate fibroblasts and recruit MSCs to the TME are largely unknown, but likely include deposition of a pro-tumorigenic secretome. The secreted embryonic protein NODAL is clinically associated with breast cancer stage and promotes tumor growth, metastasis, and vascularization. Herein, we show that NODAL expression correlates with the presence of activated fibroblasts in human triple-negative breast cancers and that it directly induces Cancer-associated fibroblasts phenotypes. We further show that NODAL reprograms cancer cell secretomes by simultaneously altering levels of chemokines (e.g., CXCL1), cytokines (e.g., IL-6) and growth factors (e.g., PDGFRA), leading to alterations in MSC chemotaxis. We therefore demonstrate a hitherto unappreciated mechanism underlying the dynamic regulation of the TME.

ADAM protease inhibition overcomes resistance of breast cancer stem-like cells to γδ T cell immunotherapy.

Gamma delta T cells (γδTc) have tremendous anti-tumoral activity, thus γδTc immunotherapy is currently under development for various malignancies. We targeted breast cancer stem-like cells (BCSC), a rare cell population responsible for patient mortality. BCSC were mostly susceptible to γδTc immunotherapy, yet some escaped. The BCSC secretome rendered γδTc hypo-responsive, and resistant BCSC expressed more PD-L1 and anti-apoptotic protein MCL-1 than non-stem-like cells (NSC). BCSC resistance was partially overcome by dMCL1-2, an MCL-1 degrader, or more fully by blocking PD-1 on γδTc. Increased MICA shedding was prevented by the ADAM inhibitor GW280264X, rendering BCSC as sensitive to γδTc cytotoxicity as NSC. Our data show promising potential for γδTc immunotherapy against BCSC while unraveling immune evasion mechanisms exploited by BCSC, which likely also enable their resistance to cytotoxic T and NK cells. Overcoming this resistance, as we have done here, will improve cancer immunotherapy, leading to better cancer patient outcomes.

Aberrantly Expressed Embryonic Protein NODAL Alters Breast Cancer Cell Susceptibility to γδ T Cell Cytotoxicity.

Gamma delta (γδ) T cells kill transformed cells, and increased circulating γδ T cells levels correlate with improved outcome in cancer patients; however, their function within the breast tumor microenvironment (TME) remains controversial. As tumors progress, they begin to express stem-cell associated proteins, concomitant with the emergence of therapy resistant metastatic disease. For example, invasive breast cancers often secrete the embryonic morphogen, NODAL. NODAL has been shown to promote angiogenesis, therapy resistance and metastasis in breast cancers. However, to date, little is known about how this secreted protein may interact with cells in the TME. Herein we explore how NODAL in the TME may influence γδ T cell function. We have assessed the proximity of γδ T cells to NODAL in a cohort of triple negative breast tumors. In all cases in which γδ T cells could be identified in these tumors, γδ T cells were found in close proximity to NODAL-expressing tumor cells. Migration of γδ and αß T cells was similar toward MDA-MB-231 cells in which NODAL had been knocked down (shN) and MDA-MB-231 scrambled control cells (shC). Furthermore, Vδ1 γδ T cells did not migrate preferentially toward conditioned medium from these cell lines. While 24-h exposure to NODAL did not impact CD69, PD-1, or T cell antigen receptor (TCR) expression on γδ T cells, long term exposure resulted in decreased Vδ2 TCR expression. Maturation of γδ T cells was not significantly influenced by NODAL stimulation. While neither short- nor long-term NODAL stimulation impacted the ability of γδ T cells to kill MCF-7 breast cancer cells, the absence of NODAL resulted in greater sensitivity of targets to γδ T cell cytotoxicity, while overexpression of NODAL conferred resistance. This appeared to be at least in part due to an inverse correlation between NODAL and surface MICA/B expression on breast cancer target lines. As such, it appears that NODAL may play a role in strategies employed by breast cancer cells to evade γδ T cell targeting, and this should be considered in the development of safe and effective γδ T cell immunotherapies.

Translational control of breast cancer plasticity.

Plasticity of neoplasia, whereby cancer cells attain stem-cell-like properties, is required for disease progression and represents a major therapeutic challenge. We report that in breast cancer cells NANOG, SNAIL and NODAL transcripts manifest multiple isoforms characterized by different 5' Untranslated Regions (5'UTRs), whereby translation of a subset of these isoforms is stimulated under hypoxia. The accumulation of the corresponding proteins induces plasticity and "fate-switching" toward stem cell-like phenotypes. Mechanistically, we observe that mTOR inhibitors and chemotherapeutics induce translational activation of a subset of NANOG, SNAIL and NODAL mRNA isoforms akin to hypoxia, engendering stem-cell-like phenotypes. These effects are overcome with drugs that antagonize translational reprogramming caused by eIF2α phosphorylation (e.g. ISRIB), suggesting that the Integrated Stress Response drives breast cancer plasticity. Collectively, our findings reveal a mechanism of induction of plasticity of breast cancer cells and provide a molecular basis for therapeutic strategies aimed at overcoming drug resistance and abrogating metastasis.

Suppressive activity of Vδ2+ γδ T cells on αß T cells is licensed by TCR signaling and correlates with signal strength.

Despite recent progress in the understanding of γδ T cells' roles and functions, their interaction with αß T cells still remains to be elucidated. In this study, we sought to clarify what precisely endows peripheral Vδ2+ T cells with immunosuppressive function on autologous αß T cells. We found that negatively freshly isolated Vδ2+ T cells do not exhibit suppressive behavior, even after stimulation with IL-12/IL-18/IL-15 or the sheer contact with butyrophilin-3A1-expressing tumor cell lines (U251 or SK-Mel-28). On the other hand, Vδ2+ T cells positively isolated through TCR crosslinking or after prolonged stimulation with isopentenyl pyrophosphate (IPP) mediate strong inhibitory effects on αß T cell proliferation. Stimulation with IPP in the presence of IL-15 induces the most robust suppressive phenotype of Vδ2+ T cells. This indicates that Vδ2+ T cells' suppressive activity is dependent on a TCR signal and that the degree of suppression correlates with its strength. Vδ2+ T cell immunosuppression does not correlate with their Foxp3 expression but rather with their PD-L1 protein expression, evidenced by the massive reduction of suppressive activity when using a blocking antibody. In conclusion, pharmacologic stimulation of Vδ2+ T cells via the Vδ2 TCR for activation and expansion induces Vδ2+ T cells' potent killer activity while simultaneously licensing them to suppress αß T cell responses. Taken together, the study is a further step to understand-in more detail-the suppressive activity of Vδ2+ γδ T cells.

Proteomics-Derived Biomarker Panel Improves Diagnostic Precision to Classify Endometrioid and High-grade Serous Ovarian Carcinoma.

PURPOSE: Ovarian carcinomas are a group of distinct diseases classified by histotypes. As histotype-specific treatment evolves, accurate classification will become critical for optimal precision medicine approaches. EXPERIMENTAL DESIGN: To uncover differences between the two most common histotypes, high-grade serous (HGSC) and endometrioid carcinoma, we performed label-free quantitative proteomics on freshly frozen tumor tissues (HGSC, n = 10; endometrioid carcinoma, n = 10). Eight candidate protein biomarkers specific to endometrioid carcinoma were validated by IHC using tissue microarrays representing 361 cases of either endometrioid carcinoma or HGSC. RESULTS: More than 500 proteins were differentially expressed (P < 0.05) between endometrioid carcinoma and HGSC tumor proteomes. A ranked set of 106 proteins was sufficient to correctly discriminate 90% of samples. IHC validated KIAA1324 as the most discriminatory novel biomarker for endometrioid carcinoma. An 8-marker panel was found to exhibit superior performance for discriminating endometrioid carcinoma from HGSC compared with the current standard of WT1 plus TP53 alone, improving the classification rate for HGSC from 90.7% to 99.2%. Endometrioid carcinoma-specific diagnostic markers such as PLCB1, KIAA1324, and SCGB2A1 were also significantly associated with favorable prognosis within endometrioid carcinoma suggesting biological heterogeneity within this histotype. Pathway analysis of proteomic data revealed differences between endometrioid carcinoma and HGSC pertaining to estrogen and interferon signalling. CONCLUSIONS: In summary, these findings support the use of multi-marker panels for the differential diagnosis of difficult cases resembling endometrioid carcinoma and HGSC.

Patient derived renal cell carcinoma xenografts exhibit distinct sensitivity patterns in response to antiangiogenic therapy and constitute a suitable tool for biomarker development.

Systemic treatment is necessary for one third of patients with renal cell carcinoma. No valid biomarker is currently available to tailor personalized therapy. In this study we established a representative panel of patient derived xenograft (PDX) mouse models from patients with renal cell carcinomas and determined serum levels of high mobility group B1 (HMGB1) protein under treatment with sunitinib, pazopanib, sorafenib, axitinib, temsirolimus and bevacizumab. Serum HMGB1 levels were significantly higher in a subset of the PDX collection, which exhibited slower tumor growth during subsequent passages than tumors with low HMGB1 serum levels. Pre-treatment PDX serum HMGB1 levels also correlated with response to systemic treatment: PDX models with high HMGB1 levels predicted response to bevacizumab. Taken together, we provide for the first time evidence that the damage associated molecular pattern biomarker HMGB1 can predict response to systemic treatment with bevacizumab. Our data support the future evaluation of HMGB1 as a predictive biomarker for bevacizumab sensitivity in patients with renal cell carcinoma.

Functional Plasticity of Gamma Delta T Cells and Breast Tumor Targets in Hypoxia.

Interactions between immune and tumor cells in the tumor microenvironment (TME) often impact patient outcome, yet remain poorly understood. In addition, the effects of biophysical features such as hypoxia [low oxygen (O2)] on cells within the TME may lead to tumor evasion. Gamma delta T cells (γδTcs) naturally kill transformed cells and are therefore under development as immunotherapy for various cancers. Clinical trials have proven the safety of γδTc immunotherapy and increased circulating γδTc levels correlate with improved patient outcome. Yet, the function of γδTc tumor infiltrating lymphocytes in human breast cancer remains controversial. Breast tumors can be highly hypoxic, thus therapy must be effective under low O2 conditions. We have found increased infiltration of γδTc in areas of hypoxia in a small cohort of breast tumors; considering their inherent plasticity, it is important to understand how hypoxia influences γδTc function. In vitro, the cell density of expanded primary healthy donor blood-derived human γδTc decreased in response to hypoxia (2% O2) compared to normoxia (20% O2). However, the secretion of macrophage inflammatory protein 1α (MIP1α)/MIP1ß, regulated on activation, normal T cell expressed and secreted (RANTES), and CD40L by γδTc were increased after 40 h in hypoxia compared to normoxia concomitant with the stabilization of hypoxia inducible factor 1-alpha protein. Mechanistically, we determined that natural killer group 2, member D (NKG2D) on γδTc and the NKG2D ligand MHC class I polypeptide-related sequence A (MICA)/B on MCF-7 and T47D breast cancer cell lines are important for γδTc cytotoxicity, but that MIP1α, RANTES, and CD40L do not play a direct role in cytotoxicity. Hypoxia appeared to enhance the cytotoxicity of γδTc such that exposure for 48 h increased cytotoxicity of γδTc against breast cancer cells that were maintained in normoxia; conversely, breast cancer lines incubated in hypoxia for 48 h prior to the assay were largely resistant to γδTc cytotoxicity. MICA/B surface expression on both MCF-7 and T47D remained unchanged upon exposure to hypoxia; however, ELISAs revealed increased MICA shedding by MCF-7 under hypoxia, potentially explaining resistance to γδTc cytotoxicity. Despite enhanced γδTc cytotoxicity upon pre-incubation in hypoxia, these cells were unable to overcome hypoxia-induced resistance of MCF-7. Thus, such resistance mechanisms employed by breast cancer targets must be overcome to develop more effective γδTc immunotherapies.

Integral Roles for Integrins in γδ T Cell Function.

Integrins are adhesion receptors on the cell surface that enable cells to respond to their environment. Most integrins are heterodimers, comprising α and ß type I transmembrane glycoprotein chains with large extracellular domains and short cytoplasmic tails. Integrins deliver signals through multiprotein complexes at the cell surface, which interact with cytoskeletal and signaling proteins to influence gene expression, cell proliferation, morphology, and migration. Integrin expression on γδ T cells (γδTc) has not been systematically investigated; however, reports in the literature dating back to the early 1990s reveal an understated role for integrins in γδTc function. Over the years, integrins have been investigated on resting and/or activated peripheral blood-derived polyclonal γδTc, γδTc clones, as well as γδ T intraepithelial lymphocytes. Differences in integrin expression have been found between αß T cells (αßTc) and γδTc, as well as between Vδ1 and Vδ2 γδTc. While most studies have focused on human γδTc, research has also been carried out in mouse and bovine models. Roles attributed to γδTc integrins include adhesion, signaling, activation, migration, tissue localization, tissue retention, cell spreading, cytokine secretion, tumor infiltration, and involvement in tumor cell killing. This review attempts to encompass all reports of integrins expressed on γδTc published prior to December 2017, highlights areas warranting further investigation, and discusses the relevance of integrin expression for γδTc function.

Apoptosis Induced via Gamma Delta T Cell Antigen Receptor "Blocking" Antibodies: A Cautionary Tale.

Mechanistic studies contribute greatly to our understanding of γδ T cell (γδTc) biology, aiding development of these cells as immunotherapeutic agents. The antibody blocking assay is an accepted method to determine the receptors involved in γδTc killing of tumor targets. Effectors and/or targets are preincubated with microgram quantities of monoclonal antibodies (mAb), often described by commercial sources to be useful for blocking assays. We and others have used such assays extensively in the past, correlating decreases in cytotoxicity against specific targets with involvement of the blocked receptor(s). However, we wondered whether other mechanisms might be at play beyond cytotoxicity inhibition. Indeed, administration of certain "blocking" mAb to the γδ T cell antigen receptor (γδTCR) induced γδTc death. Upon further investigation, we discovered that γδTc underwent apoptosis triggered by incubation with mAb to the γδTCR. This effect was specific, as no apoptosis was observed when αß T cells (αßTc) were incubated with these mAb. Apoptosis was further potentiated by the presence of interleukin (IL)-2, often included in cytotoxicity assays; however, exogenous interleukin-2 (IL-2) did not contribute significantly to γδTc cytotoxicity against breast cancer cell lines. Here, we have investigated the usefulness of four mAb for use in blocking assays by assessing blocking properties in conjunction with their propensity to induce apoptosis in cultured primary human γδTc. We found that the 5A6.E9 clone was usually a better alternative to the commonly used B1 (or B1.1) and 11F2 clones; however, some variability in susceptibility to apoptosis induction was observed among donor cultures. Thus, viability assessment of primary effector cells treated with mAb alone should be undertaken in parallel with cytotoxicity assays employing blocking antibodies, to account for cytotoxicity reduction caused by effector cell death. Previous findings should be reassessed in this light.

CD11d ß2 integrin expression on human NK, B, and γδ T cells.

The CD11d integrin is expressed on the cell surface of leukocytes that belong to the myeloid lineage, but its expression on lymphocytes remains unexplored. To test the hypothesis that CD11d is expressed on lymphocyte subsets, we employed a multicolor flow cytometry panel to identify CD11d expression on B, NK, CD4+ and CD8+ αß T cells (αßTc), and γδ T cells (γδTc) in human PBMC samples. CD11d was highly expressed on NK cells, B cells, and γδTc, but not αßTc. CD11d expression was higher on freshly isolated γδTc compared with αßTc from healthy donors, yet both inter- and intradonor variability was evident. Over time in primary culture, we consistently observed higher CD11d levels on γδTc compared with αßTc from the same donor. Furthermore, CD11d expression on γδTc increased over time and correlated with levels of IL-2 supplementation. Of interest, a greater percentage of Vδ1 γδTc expressed CD11d than did Vδ2 γδTc, which suggested differential roles for this integrin that may segregate with γδTc subsets. These results expand the potential for CD11d to regulate lymphocyte migration and tissue retention, and illuminate the possibility of a previously unconsidered role for CD11d in leukocyte biology and disease.

Pre-Labeling of Immune Cells in Normal Bone Marrow and Spleen for Subsequent Cell Tracking by MRI.

Iron particles are intravenously (IV) administered to label cells in vivo during magnetic resonance imaging. This technique has been extensively used to monitor immune cells in the context of inflammatory diseases. Here, we have investigated whether resting immune cells can be labeled in vivo in healthy mice before disease onset or injury, thus allowing visualization of critical early cellular events. Using 1.5 T magnetic resonance imaging, we were able to detect signal loss in bone marrow, liver, and spleen as early as 1 hour after the IV injection of superparamagnetic iron oxide nanoparticles (Feridex; 80 to 120 nm in diameter) or larger micron-sized iron oxide particles (Bangs; 0.9 µm in diameter). Results were confirmed via histology. Further, flow cytometric analysis confirmed the presence of iron-labeled CD19+ B cells, CD3+ T cells, and CD11b + myeloid cells within the spleen and the bone marrow. Extending this work to a murine model of multiple sclerosis, we IV administered superparamagnetic iron oxide to healthy mice 1 week before inducing experimental autoimmune encephalomyelitis. Images acquired 1 week after the onset of hindlimb paralysis showed regions of signal hypointensity in the mouse brain that corresponded with iron-labeled macrophages. In summary, we show that resting immune cells in the healthy mouse liver, spleen, and bone marrow can be prelabeled with iron oxide nanoparticles. Furthermore, iron oxide preloading of immune cells in the reticuloendothelial system can be used to detect cellular infiltration in the brains of experimental autoimmune encephalomyelitis mice.

Cytotoxic and regulatory properties of circulating Vδ1+ γδ T cells: a new player on the cell therapy field?

Exploration of cancer immunotherapy strategies that incorporate γδ T cells as primary mediators of antitumor immunity are just beginning to be explored and with a primary focus on the use of manufactured phosphoantigen-stimulated Vγ9Vδ2 T cells. Increasing evidence, however, supports a critical role for Vδ1+ γδ T cells, a minor subset in peripheral blood with distinct innate recognition properties that possess powerful tumoricidal activity. They are activated by a host of ligands including stress-induced self-antigens, glycolipids presented by CD1c/d, and potentially many others that currently remain unidentified. In contrast to Vγ9Vδ2 T cells, tumor-reactive Vδ1+ T cells are not as susceptible to activation-induced cell death and can persist in the circulation for many years, potentially offering durable immunity to some cancers. In addition, specific populations of Vδ1+ T cells can also exhibit immunosuppressive and regulatory properties, a function that can also be exploited for therapeutic purposes. This review explores the biology, function, manufacturing strategies, and potential therapeutic role of Vδ1+ T cells. We also discuss clinical experience with Vδ1+ T cells in the setting of cancer, as well as the potential of and barriers to the development of Vδ1+ T cell-based adoptive cell therapy strategies.

The CD3 conformational change in the γδ T cell receptor is not triggered by antigens but can be enforced to enhance tumor killing.

Activation of the T cell receptor (TCR) by antigen is the key step in adaptive immunity. In the αßTCR, antigen induces a conformational change at the CD3 subunits (CD3 CC) that is absolutely required for αßTCR activation. Here, we demonstrate that the CD3 CC is not induced by antigen stimulation of the mouse G8 or the human Vγ9Vδ2 γδTCR. We find that there is a fundamental difference between the activation mechanisms of the αßTCR and γδTCR that map to the constant regions of the TCRαß/γδ heterodimers. Enforced induction of CD3 CC with a less commonly used monoclonal anti-CD3 promoted proximal γδTCR signaling but inhibited cytokine secretion. Utilizing this knowledge, we could dramatically improve in vitro tumor cell lysis by activated human γδ T cells. Thus, manipulation of the CD3 CC might be exploited to improve clinical γδ T cell-based immunotherapies.

Intratibial injection of human multiple myeloma cells in NOD/SCID IL-2Rγ(null) mice mimics human myeloma and serves as a valuable tool for the development of anticancer strategies.

BACKGROUND: We systematically analyzed multiple myeloma (MM) cell lines and patient bone marrow cells for their engraftment capacity in immunodeficient mice and validated the response of the resulting xenografts to antimyeloma agents. DESIGN AND METHODS: Using flow cytometry and near infrared fluorescence in-vivo-imaging, growth kinetics of MM cell lines L363 and RPMI8226 and patient bone marrow cells were investigated with use of a murine subcutaneous bone implant, intratibial and intravenous approach in NOD/SCID, NOD/SCID treated with CD122 antibody and NOD/SCID IL-2Rγ(null) mice (NSG). RESULTS: Myeloma growth was significantly increased in the absence of natural killer cell activity (NSG or αCD122-treated NOD/SCID). Comparison of NSG and αCD122-treated NOD/SCID revealed enhanced growth kinetics in the former, especially with respect to metastatic tumor sites which were exclusively observed therein. In NSG, MM cells were more tumorigenic when injected intratibially than intravenously. In NOD/SCID in contrast, the use of juvenile long bone implants was superior to intratibial or intravenous cancer cell injection. Using the intratibial NSG model, mice developed typical disease symptoms exclusively when implanted with human MM cell lines or patient-derived bone marrow cells, but not with healthy bone marrow cells nor in mock-injected animals. Bortezomib and dexamethasone delayed myeloma progression in L363- as well as patient-derived MM cell bearing NSG. Antitumor activity could be quantified via flow cytometry and in vivo imaging analyses. CONCLUSIONS: Our results suggest that the intratibial NSG MM model mimics the clinical situation of the disseminated disease and serves as a valuable tool in the development of novel anticancer strategies.

Illuminating luminal B: QSOX1 as a subtype-specific biomarker.

Breast cancer is a complex and heterogeneous disease that affects about one out of every eight women. In the last decade, several advancements have been made that have increased our understanding of breast cancer and have allowed us to more accurately diagnose and treat this disease in a more targeted manner. For example, gene expression profiling enabled the classification of breast cancers into four main subtypes - basal-like, HER2+ (human epidermal growth factor receptor 2-positive), luminal A and luminal B - and this classification is used to direct the use of targeted therapies such as tamoxifen or trastuzumab. The luminal subtypes are generally characterized as being estrogen receptor-positive and targetable with anti-hormone therapies. However, whereas luminal A cancers have a good prognosis, luminal B cancers are associated with early relapse following endocrine therapy and a prognosis that is similar to that of the aggressive basal subtype. It is thus imperative that luminal B cancers be better characterized so that therapeutic targets and biomarkers for this disease type can be realized. In the previous issue of Breast Cancer Research, Katchman and colleagues address this need by demonstrating that quiescin sulfydryl oxidase 1 (QSOX1), a secreted enzyme involved in post-translational modifications, is associated with poor prognosis in patients with luminal B breast cancer. The authors further determined that this protein promotes breast cancer proliferation and invasion. Collectively, these studies suggest that QSOX1 is a predictive biomarker for luminal cancers and that it may be a useful target for elusive luminal B disease.