Tipping the immunostimulatory and inhibitory DAMP balance to harness immunogenic cell death

Induction of tumor cell death is the therapeutic goal for most anticancer drugs. Yet, a mode of drug-induced cell death, known as immunogenic cell death (ICD), can propagate antitumoral immunity to augment therapeutic efficacy. Currently, the molecular hallmark of ICD features the release of damage-associated molecular patterns (DAMPs) by dying cancer cells. Here, we show that gemcitabine, a standard chemotherapy for various solid tumors, triggers hallmark immunostimualtory DAMP release (e.g., calreticulin, HSP70, and HMGB1); however, is unable to induce ICD. Mechanistic studies reveal gemcitabine concurrently triggers prostaglandin E2 release as an inhibitory DAMP to counterpoise the adjuvanticity of immunostimulatory DAMPs. Pharmacological blockade of prostaglandin E2 biosythesis favors CD103+ dendritic cell activation that primes a Tc1-polarized CD8+ T cell response to bolster tumor rejection. Herein, we postulate that an intricate balance between immunostimulatory and inhibitory DAMPs could determine the outcome of drug-induced ICD and pose COX-2/prostaglandin E2 blockade as a strategy to harness ICD.

Collagen-rich airway smooth muscle cells are a metastatic niche for tumor colonization in the lung

Metastases account for the majority of cancer deaths. While certain steps of the metastatic cascade are well characterized, identification of targets to block this process remains a challenge. Host factors determining metastatic colonization to secondary organs are particularly important for exploration, as those might be shared among different cancer types. Here, we showed that bladder tumor cells expressing the collagen receptor, CD167a, responded to collagen I stimulation at the primary tumor to promote local invasion and utilized the same receptor to preferentially colonize at airway smooth muscle cells (ASMCs)—a rich source of collagen III in lung. Morphologically, COL3-CD167a-driven metastatic foci are uniquely distinct from typical lung alveolar metastatic lesions and exhibited activation of the CD167a-HSP90-Stat3 axis. Importantly, metastatic lung colonization could be abrogated using an investigational drug that attenuates Stat3 activity, implicating this seed-and-soil interaction as a therapeutic target for eliminating lung metastasis.

Collagen is a dynamic component of both the tumor and metastatic niche. Here, the authors show that airway smooth muscle cells are a collagen III rich niche bladder cancer cells expressing CD167a, and Stat3 is a downstream target for abrogating  these collagen III/CD167a-driven metastatic foci.

Cellular Hierarchy as a Determinant of Tumor Sensitivity to Chemotherapy

Chemotherapy has been shown to enrich cancer stem cells in tumors. Recently, we demonstrated that administration of chemotherapy to human bladder cancer xenografts could trigger a wound-healing response that mobilizes quiescent tumor stem cells into active proliferation. This phenomenon leads to a loss of sensitivity to chemotherapy partly due to an increase in the number of tumor stem cells, which typically respond to chemotherapy-induced cell death less than more differentiated cells. Different bladder cancer xenografts, however, demonstrate differential sensitivities to chemotherapy, the basis of which is not understood. Using mathematical models, we show that characteristics of the tumor cell hierarchy can be crucial for determining the sensitivity of tumors to drug therapy, under the assumption that stem cell enrichment is the primary basis for drug resistance. Intriguingly, our model predicts a weaker response to therapy if there is negative feedback from differentiated tumor cells that inhibits the rate of tumor stem cell division. If this negative feedback is less pronounced, the treatment response is predicted to be enhanced. The reason is that negative feedback on the rate of tumor cell division promotes a permanent rise of the tumor stem cell population over time, both in the absence of treatment and even more so during drug therapy. Model application to data from chemotherapy-treated patient-derived xenografts indicates support for model predictions. These findings call for further research into feedback mechanisms that might remain active in cancers and potentially highlight the presence of feedback as an indication to combine chemotherapy with approaches that limit the process of tumor stem cell enrichment. Cancer Res; 77(9); 2231-41. ©2017 AACR.

Abstract 5470: Blocking wound-induced tumor repopulation between chemotherapy cycles as a novel approach to abrogate chemoresistance

Acquired chemoresistance remains a major clinical issue in the management of advanced solid cancers. Initial response to cytotoxic chemotherapy is common, but certain patients progressively become unresponsive after multiple chemotherapy cycles. While causes of drug resistance are multiple and complex, here we approach this problem from a new angle: we studied whether repopulation of residual surviving cancer cells between chemotherapy cycles contributes to progressive chemoresistance. Currently the identity of repopulating cancer cells following chemotherapy is unknown, and the underlying molecular mechanisms that initiate tumor repopulation remain poorly understood. In the present study we use bladder cancer as a model and report that quiescent cancer stem cells (CSCs) are unexpectedly recruited to proliferate and repopulate residual tumors in response to chemotherapy-induced damage. This phenomenon is similar to how normal resident tissue stem cells mobilize to wound sites for tissue repair. We further investigate whether blockade of this wound-induced CSC repopulation can provide an innovative approach to abrogate chemoresistance.

Previously we showed that cytokeratin 14 (CK14) marks the most primitive bladder cancer cells and abundance of CK14+ cancer cells in patients correlates with poor survival. Here, we followed the standard clinical chemotherapy regimen with gap periods to allow recovery of normal tissues between treatment cycles. While one cycle of gemcitabine and cisplatin effectively reduced tumor growth in vivo, a generalized expansion of CK14+ CSCs occurred in residual tumors during these gap periods between cycles. Further analysis revealed the induction of a “wound-response” gene signature in residual tumors and active recruitment of quiescent CSCs into proliferation in response to chemotherapy-induced damage. We demonstrated that prostaglandin E2 (PGE2) released by neighboring dying cancer cells could induce CSC expansion in a paracrine manner. This undesirable CSC expansion could be abrogated by a PGE2 neutralizing antibody and Celecoxib, an FDA approved COX2 inhibitor that blocks PGE2 signaling. In vivo administration of Celecoxib blocked the induction of “wound-response” gene signature and significantly attenuated progressive development of chemoresistance in xenograft tumors, including primary xenografts derived from a patient who failed chemotherapy.These results revealed a new mechanism by which CSCs contribute to therapeutic resistance via repopulating residual tumors between chemotherapy cycles. Repopulation was initiated by dying cells that induced wound response and recruitment of CSCs to repair chemotherapy-induced damages. Therapeutic intervention with Celecoxib effectively blocked this process and improved chemotherapeutic response in bladder tumors, supporting further validation in other solid cancers.

Citation Format: Antonina V. Kurtova, Jing Xiao, Qianxing Mo, Senthil Pazhanisamy, Ross Krasnow, Seth P. Lerner, Fengju Chen, Terrence Roh, Erica Lay, Philip L. Ho, Keith S. Chan. Blocking wound-induced tumor repopulation between chemotherapy cycles as a novel approach to abrogate chemoresistance. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5470. doi:10.1158/1538-7445.AM2015-5470

Abstract 4801: Stromal-mediated collagen I signal in promoting bladder cancer progression

Bladder cancer is the fifth most common malignancy, which is mostly incurable as invasive disease. It is clinically important to study the mechanisms underlying bladder cancer progression. While the tumor microenvironment is widely established to play an active role in epithelial cancers, its contribution to bladder cancer remains unexplored. The presence of cancer-associated fibroblasts (CAFs), characterized by the co-expression of vimentin, alpha-smooth muscle actin, and tenascin C, has been associated with invasive bladder cancer. Nevertheless, functional contributions of CAFs to bladder cancer progression have not been studied.

Here,we report the successful isolation and molecular characterization of bladder CAFs. We further investigate their functional roles on bladder cancer progression, with an emphasis on stromal secreted collagen I in the paracrine activation of discoidin domain receptor (DDR1) signaling in neighboring bladder cancer cells.

Using bioinformatics analysis we found that invasive bladder cancer patients with elevated expression of CAF genes have a poorer survival than those with lower CAF gene expression. Subsequently, we isolated and characterized CAFs from patient-derived tissues. Co-transplantation of CAFs and bladder cancer cells as xenograft tumors revealed high collagen I (COL1) deposition in these tumors formed, while molecular analyses uncovered CAFs as the primary source of COL1. Further experiments verified that COL1 as a single extracellular matrix component could phenocopy the tumor phenotype resembling those co-transplanted with CAFs and cancer cells. Further, pre-stimulation with COL1 could also enhance metastatic colonization of bladder cancer cells to lung. Molecular analysis of these COL1 stimulated cancer cells revealed up-regulation of the collagen receptor DDR1, but not integrins. Immunohistochemical analysis confirmed the presence of DDR1+ cancer cells adjacent to CAFs in the primary tumor site, with enhanced and exclusive expression of DDR1 in paired lung metastasis. Oncomine analysis showed that invasive bladder cancer expressed higher mRNA levels of COL1 and DDRs than non-invasive cancer, indicating that collagen I-DDR1 interaction may be a generalized phenomenon during invasive bladder cancer progression. To delineate the molecular mechanism downstream to collagen I-DDR1 we studied the interaction of DDR1 and STAT3, a factor we previously reported to drive invasive bladder cancer progression. Stimulation of bladder cancer cells with COL1 revealed a time kinetic increase in total and activated DDR1 protein associated with STAT3 phosphorylation. Further analysis of lung metastasis confirmed the co-localization of DDR1 and nuclear active STAT3. Collectively, these findings uncovered a role of CAFs in bladder cancer progression via stromal mediated collagen I signaling and warrant further analysis of therapeutic options to target signaling components downstream to collagen I.

Citation Format: Antonina V. Kurtova, Jing Xiao, Erica J. Lay, Qianxing Mo, Seth P. Lerner, David R. Rowley, Keith S. Chan. Stromal-mediated collagen I signal in promoting bladder cancer progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4801. doi:10.1158/1538-7445.AM2014-4801

CD49d is the strongest flow cytometry-based predictor of overall survival in chronic lymphocytic leukemia

PURPOSE

Although CD49d is an unfavorable prognostic marker in chronic lymphocytic leukemia (CLL), definitive validation evidence is lacking. A worldwide multicenter analysis was performed using published and unpublished CLL series to evaluate the impact of CD49d as an overall (OS) and treatment-free survival (TFS) predictor.

PATIENTS AND METHODS

A training/validation strategy was chosen to find the optimal CD49d cutoff. The hazard ratio (HR) for death and treatment imposed by CD49d was estimated by pooled analysis of 2,972 CLLs; Cox analysis stratified by center and stage was used to adjust for confounding variables. The importance of CD49d over other flow cytometry-based prognosticators (eg, CD38, ZAP-70) was ranked by recursive partitioning.

RESULTS

Patients with ≥ 30% of neoplastic cells expressing CD49d were considered CD49d+. Decrease in OS at 5 and 10 years among CD49d+ patients was 7% and 23% (decrease in TFS, 26% and 25%, respectively). Pooled HR of CD49d for OS was 2.5 (2.3 for TFS) in univariate analysis. This HR remained significant and of similar magnitude (HR, 2.0) in a Cox model adjusted for clinical and biologic prognosticators. Hierarchic trees including all patients or restricted to those with early-stage disease or those age ≤ 65 years always selected CD49d as the most important flow cytometry-based biomarker, with negligible additional prognostic information added by CD38 or ZAP-70. Consistently, by bivariate analysis, CD49d reliably identified patient subsets with poorer outcome independent of CD38 and ZAP-70.

CONCLUSION

In this analysis of approximately 3,000 patients, CD49d emerged as the strongest flow cytometry-based predictor of OS and TFS in CLL.

B-cell antigen receptor signaling enhances chronic lymphocytic leukemia cell migration and survival: specific targeting with a novel spleen tyrosine kinase inhibitor, R406

Antigenic stimulation through the B-cell antigen receptor (BCR) is considered to promote the expansion of chronic lymphocytic leukemia (CLL) B cells. The spleen tyrosine kinase (Syk), a key component of BCR signaling, can be blocked by R406, a small-molecule Syk inhibitor, that displayed activity in CLL patients in a first clinical trial. In this study, we investigated the effects of BCR stimulation and R406 on CLL cell survival and migration. The prosurvival effects promoted by anti-IgM stimulation and nurselike cells were abrogated by R406. BCR triggering up-regulated adhesion molecules, and increased CLL cell migration toward the chemokines CXCL12 and CXCL13. BCR activation also enhanced CLL cell migration beneath marrow stromal cells. These responses were blocked by R406, which furthermore abrogated BCR-dependent secretion of T-cell chemokines (CCL3 and CCL4) by CLL cells. Finally, R406 inhibited constitutive and BCR-induced activation of Syk, extracellular signal-regulated kinases, and AKT, and blocked BCR-induced calcium mobilization. These findings suggest that BCR activation favors CLL cell homing, retention, and survival in tissue microenvironments. R406 effectively blocks these BCR-dependent responses in CLL cells, providing an explanation for the activity of R406 in patients with CLL.

[Bone marrow immunophenotyping for the diagnosis of multiple myeloma: practical aspects]

Multiple myeloma is a malignant proliferative disease of plasma cells. Flow cytometric immunophenotyping makes it possible to identify a malignant clone of myeloma cells in the shortest possible time, to determine its phenotype, and differentiate transformed and preserved plasma cells. The article presents an immunophenotyping strategy using three-color monoclonal antibodies (CD35, CD14, CD38, CD138, and CD19) and an algorithm of verification of transformed plasma cells. Particular emphasis is placed on both the practical aspects of performing this assay and on the clinical application of the obtained results.