Kristen Palmer

Individualized vaccination of AML patients in remission is associated with induction of antileukemia immunity and prolonged remissions

A personalized DC/AML fusion cell vaccine promotes the expansion of leukemia-specific T cells and prolonged remission in patients. Immune cells join leukemia then beat it Acute myeloid leukemia (AML) is an aggressive hematologic cancer. The only curative treatment available for this disease is hematopoietic stem cell transplantation, which can result in donor immune cells helping to eradicate the cancer. Unfortunately, this procedure is not always effective and is itself associated with numerous complications and risk of death. Rosenblatt et al. have identified a potentially better way to stimulate an immune response against AML by fusing patients’ own leukemia cells with dendritic cells. The resulting fusion cells were very effective at presenting tumor antigens to T cells, resulting in a strong antitumor T cell response and prolonged survival in human patients. We developed a personalized cancer vaccine in which patient-derived acute myeloid leukemia (AML) cells are fused with autologous dendritic cells, generating a hybridoma that potently stimulates broad antitumor responses. We report results obtained from the first 17 AML patients, who achieved remission after chemotherapy and were then serially vaccinated to target minimal residual disease and prevent relapse. Vaccination was well tolerated and induced inflammatory responses at the site of administration, characterized by the dense infiltration of T cells. Vaccination was also associated with a marked rise in circulating T cells recognizing whole AML cells and leukemia-specific antigens that persisted for more than 6 months. Twelve of 17 vaccinated patients (71%; 90% confidence interval, 52 to 89%) remain alive without recurrence at a median follow-up of 57 months. The results demonstrate that personalized vaccination of AML patients in remission induces the expansion of leukemia-specific T cells and may be protective against disease relapse.

Mucin 1 is a potential therapeutic target in cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) is an aggressive neoplasm with limited treatments for patients with advanced disease. The mucin 1 C-terminal subunit (MUC1-C) oncoprotein plays a critical role in regulating cell proliferation, apoptosis, and protection from cytotoxic injury mediated by reactive oxygen species (ROS). Although CTCL cells exhibit resistance to ROS-induced apoptosis, the expression and functional significance of MUC1 in CTCL have not been previously investigated. Present studies demonstrate that MUC1-C is overexpressed in CTCL cell lines and primary CTCL cells but is absent in resting T cells from healthy donors and B-cell lymphoma cells. We have developed a cell-penetrating peptide that disrupts homodimerization of the MUC1-C subunit necessary for its nuclear translocation and downstream signaling. We show that treatment of CTCL cells with the MUC1-C inhibitor is associated with downregulation of the p53-inducible regulator of glycolysis and apoptosis and decreases in reduced NAD phosphate and glutathione levels. In concert with these results, targeting MUC1-C in CTCL cells increased ROS and, in turn, induced ROS-mediated late apoptosis/necrosis. Targeting MUC1-C in CTCL tumor xenograft models demonstrated significant decreases in disease burden. These findings indicate that MUC1-C maintains redox balance in CTCL cells and is thereby a novel target for the treatment of patients with CTCL.

MUC1 inhibition leads to decrease in PD-L1 levels via upregulation of miRNAs

The PD-L1/PD-1 pathway is a critical component of the immunosuppressive tumor microenvironment in acute myeloid leukemia (AML), but little is known about its regulation. We investigated the role of the MUC1 oncoprotein in modulating PD-L1 expression in AML. Silencing of MUC1 in AML cell lines suppressed PD-L1 expression without a decrease in PD-L1 mRNA levels, suggesting a post-transcriptional mechanism of regulation. We identified the microRNAs miR-200c and miR-34a as key regulators of PD-L1 expression in AML. Silencing of MUC1 in AML cells led to a marked increase in miR-200c and miR-34a levels, without changes in precursor microRNA, suggesting that MUC1 might regulate microRNA-processing. MUC1 signaling decreased the expression of the microRNA-processing protein DICER, via the suppression of c-Jun activity. NanoString (Seattle, WA, USA) array of MUC1-silenced AML cells demonstrated an increase in the majority of probed microRNAs. In an immunocompetent murine AML model, targeting of MUC1 led to a significant increase in leukemia-specific T cells. In concert, targeting MUC1 signaling in human AML cells resulted in enhanced sensitivity to T-cell-mediated lysis. These findings suggest MUC1 is a critical regulator of PD-L1 expression via its effects on microRNA levels and represents a potential therapeutic target to enhance anti-tumor immunity.

MUC1 mediated induction of myeloid-derived suppressor cells in patients with acute myeloid leukemia.

Myeloid-derived suppressor cells (MDSCs) play a critical role in promoting immune tolerance and disease growth. The mechanism by which tumor cells evoke the expansion of MDSCs in acute myeloid leukemia (AML) has not been well described. We have demonstrated that patients with AML exhibit increased presence of MDSCs in their peripheral blood, in comparison with normal controls. Cytogenetic studies demonstrated that MDSCs in patients with AML may be derived from leukemic or apparently normal progenitors. Engraftment of C57BL/6 mice with TIB-49 AML led to an expansion of CD11b+ Gr1+ MDSCs in bone marrow and spleen. Coculture of the AML cell lines MOLM-4, THP-1 or primary AML cells with donor peripheral blood mononuclear cells elicited a cell contact-dependent expansion of MDSCs. MDSCs were suppressive of autologous T-cell responses as evidenced by reduced T-cell proliferation and a switch from a Th1 to a Th2 phenotype. We hypothesized that the expansion of MDSCs in AML is accomplished by tumor-derived extracellular vesicles (EVs). Using tracking studies, we demonstrated that AML EVs are taken-up myeloid progenitor cells, resulting in the selective proliferation of MDSCs in comparison with functionally competent antigen-presenting cells. The MUC1 oncoprotein was subsequently identified as the critical driver of EV-mediated MDSC expansion. MUC1 induces increased expression of c-myc in EVs that induces proliferation in the target MDSC population via downstream effects on cell cycle proteins. Moreover, we demonstrate that the microRNA miR34a acts as the regulatory mechanism by which MUC1 drives c-myc expression in AML cells and EVs.

Dynamic analysis of immune and cancer cell interactions at single cell level in microfluidic droplets

Cell-cell communication mediates immune responses to physiological stimuli at local and systemic levels. Intercellular communication occurs via a direct contact between cells as well as by secretory contact-independent mechanisms. However, there are few existing methods that allow quantitative resolution of contact-dependent and independent cellular processes in a rapid, precisely controlled, and dynamic format. This study utilizes a high-throughput microfluidic droplet array platform to analyze cell-cell interaction and effector functions at single cell level. Controlled encapsulation of distinct heterotypic cell pairs was achieved in a single-step cell loading process. Dynamic analysis of dendritic cell (DC)-T cell interactions demonstrated marked heterogeneity in the type of contact and duration. Non-stimulated DCs and T cells interacted less frequently and more transiently while antigen and chemokine-loaded DCs and T cells depicted highly stable interactions in addition to transient and sequential contact. The effector function of CD8+ T cells was assessed via cytolysis of multiple myeloma cell line. Variable cell conjugation periods and killing time were detected irrespective of the activation of T cells, although activated T cells delivered significantly higher cytotoxicity. T cell alloreactivity against the target cells was partially mediated by secretion of interferon gamma, which was abrogated by the addition of a neutralizing antibody. These results suggest that the droplet array-based microfluidic platform is a powerful technique for dynamic phenotypic screening and potentially applicable for evaluation of novel cell-based immunotherapeutic agents.

Bone marrow stroma protects myeloma cells from cytotoxic damage via induction of the oncoprotein MUC1.

Multiple myeloma (MM) is a lethal haematological malignancy that arises in the context of a tumour microenvironment that promotes resistance to apoptosis and immune escape. In the present study, we demonstrate that co‐culture of MM cells with stromal cells results in increased resistance to cytotoxic and biological agents as manifested by decreased rates of cell death following exposure to alkylating agents and the proteosome inhibitor, bortezomib. To identify the mechanism of increased resistance, we examined the effect of the co‐culture of MM cells with stroma cells, on expression of the MUC1 oncogene, known to confer tumour cells with resistance to apoptosis and necrosis. Co‐culture of stroma with MM cells resulted in increased MUC1 expression by tumour cells. The effect of stromal cell co‐culture on MUC1 expression was not dependent on cell contact and was therefore thought to be due to soluble factors secreted by the stromal cells into the microenvironment. We demonstrated that MUC1 expression was mediated by interleukin‐6 and subsequent up‐regulation of the JAK‐STAT pathway. Interestingly, the effect of stromal cell co‐culture on tumour resistance was partially reversed by silencing of MUC1 in MM cells, consistent with the potential role of MUC1 in mediating resistance to cytotoxic‐based therapies.

MUC1‐C drives myeloid leukaemogenesis and resistance to treatment by a survivin‐mediated mechanism

Acute myeloid leukaemia (AML) is an aggressive haematological malignancy with an unmet need for improved therapies. Responses to standard cytotoxic therapy in AML are often transient because of the emergence of chemotherapy‐resistant disease. The MUC1‐C oncoprotein governs critical pathways of tumorigenesis, including self‐renewal and survival, and is aberrantly expressed in AML blasts and leukaemia stem cells (LSCs). However, a role for MUC1‐C in linking leukaemogenesis and resistance to treatment has not been described. In this study, we demonstrate that MUC1‐C overexpression is associated with increased leukaemia initiating capacity in an NSG mouse model. In concert with those results, MUC1‐C silencing in multiple AML cell lines significantly reduced the establishment of AML in vivo. In addition, targeting MUC1‐C with silencing or pharmacologic inhibition with GO‐203 led to a decrease in active β‐catenin levels and, in‐turn, down‐regulation of survivin, a critical mediator of leukaemia cell survival. Targeting MUC1‐C was also associated with increased sensitivity of AML cells to Cytarabine (Ara‐C) treatment by a survivin‐dependent mechanism. Notably, low MUC1 and survivin gene expression were associated with better clinical outcomes in patients with AML. These findings emphasize the importance of MUC1‐C to myeloid leukaemogenesis and resistance to treatment by driving survivin expression. Our findings also highlight the potential translational relevance of combining GO‐203 with Ara‐C for the treatment of patients with AML.