Phase I study of the anti-CD74 monoclonal antibody milatuzumab (hLL1) in patients with previously treated B-cell lymphomas

Therapeutic Opportunities in Breast Cancer by Targeting Macrophage Migration Inhibitory Factor as a Pleiotropic Cytokine

As a heterogeneous disease, breast cancer (BC) has been characterized by the uncontrolled proliferation of mammary epithelial cells. The tumor microenvironment (TME) also contains inflammatory cells, fibroblasts, the extracellular matrix (ECM), and soluble factors that all promote BC progression. In this sense, the macrophage migration inhibitory factor (MIF), a pleiotropic pro-inflammatory cytokine and an upstream regulator of the immune response, enhances breast tumorigenesis through escalating cancer cell proliferation, survival, angiogenesis, invasion, metastasis, and stemness, which then brings tumorigenic effects by activating key oncogenic signaling pathways and inducing immunosuppression. Against this background, this review was to summarize the current understanding of the MIF pathogenic mechanisms in cancer, particularly BC, and address the central role of this immunoregulatory cytokine in signaling pathways and breast tumorigenesis. Furthermore, different inhibitors, such as small molecules as well as antibodies (Abs) or small interfering RNA (siRNA) and their anti-tumor effects in BC studies were examined. Small molecules and other therapy target MIF. Considering MIF as a promising therapeutic target, further clinical evaluation of MIF-targeted agents in patients with BC was warranted.

Insights into the prognostic value and immunological role of CD74 in pan-cancer

BACKGROUND

CD74 is a non-polymorphic type II transmembrane glycoprotein. It is involved in the regulation of T and B cell development, and dendritic cell (DC) motility. Numerous studies have found that CD74 exerts an essential role in tumor immunity, but the expression profile of CD74 is still not systematically reported, and its value in human pan-cancer analysis is unknown. In this study, we analyzed the expression pattern of CD74 in 33 cancers, and evaluated the significance of CD74 in prognosis prediction and cancer immunity.

METHODS

Pan-cancer dataset from UCSC Xena.We used the Sangerbox website combined with R software' Timer, CIBERSORT method and IOBR package to analyze and plot the data. Survival was assessed using the Kaplan-Meier method and log-rank test for 33 cancer types (p < 0.05). In addition, to explore the relationship between CD74 expression and immune checkpoints, immune cell infiltration, tumor mutational burden (TMB) and microsatellite instability (MSI), Spearman correlation analysis was performed.

RESULTS

This study comprehensively analyzed CD74 expression in 33 different tumor types, revealing that CD74 play an crucial role in cancer formation and development.

CONCLUSIONS

CD74 gene expression in different cancers is associated with immune cell infiltration and immunomodulators and may provide a promising target for survival and immunotherapy. Our study shows that CD74 has an essential role as a biomarker of prognosis during tumor development, which highlights the possibility of new targeted therapies.

CD74 supports accumulation and function of regulatory T cells in tumors

Regulatory T cells (Tregs) are plastic cells playing a pivotal role in the maintenance of immune homeostasis. Tregs actively adapt to the microenvironment where they reside; as a consequence, their molecular and functional profiles differ among tissues and pathologies. In tumors, the features acquired by Tregs remains poorly characterized. Here, we observe that human tumor-infiltrating Tregs selectively overexpress CD74, the MHC class II invariant chain. CD74 has been previously described as a regulator of antigen-presenting cell biology, however its function in Tregs remains unknown. CD74 genetic deletion in human primary Tregs reveals that CD74KO Tregs exhibit major defects in the organization of their actin cytoskeleton and intracellular organelles. Additionally, intratumoral CD74KO Tregs show a decreased activation, a drop in Foxp3 expression, a low accumulation in the tumor, and consistently, they are associated with accelerated tumor rejection in preclinical models in female mice. These observations are unique to tumor conditions as, at steady state, CD74KO-Treg phenotype, survival, and suppressive capacity are unaffected in vitro and in vivo. CD74 therefore emerges as a specific regulator of tumor-infiltrating Tregs and as a target to interfere with Treg anti-tumor activity.

Macrophage migration inhibitory factor as a therapeutic target in neuro-oncology: A review

Primary central nervous system (CNS) tumors affect tens of thousands of patients each year, and there is a significant need for new treatments. Macrophage migration inhibitory factor (MIF) is a cytokine implicated in multiple tumorigenic processes such as cell proliferation, vascularization, and immune evasion and is therefore a promising therapeutic target in primary CNS tumors. There are several MIF-directed treatments available, including small-molecule inhibitors, peptide drugs, and monoclonal antibodies. However, only a small number of these drugs have been tested in preclinical models of primary CNS tumors, and even fewer have been studied in patients. Moreover, the brain has unique therapeutic requirements that further make effective targeting challenging. In this review, we summarize the latest functions of MIF in primary CNS tumor initiation and progression. We also discuss advances in MIF therapeutic development and ongoing preclinical studies and clinical trials. Finally, we discuss potential future MIF therapies and the strategies required for successful clinical translation.

Analysis of CD74 Occurrence in Oncogenic Fusion Proteins

CD74 is a type II cell surface receptor found to be highly expressed in several hematological and solid cancers, due to its ability to activate pathways associated with tumor cell survival and proliferation. Over the past 16 years, CD74 has emerged as a commonly detected fusion partner in multiple oncogenic fusion proteins. Studies have found CD74 fusion proteins in a range of cancers, including lung adenocarcinoma, inflammatory breast cancer, and pediatric acute lymphoblastic leukemia. To date, there are five known CD74 fusion proteins, CD74-ROS1, CD74-NTRK1, CD74-NRG1, CD74-NRG2α, and CD74-PDGFRB, with a total of 16 different variants, each with unique genetic signatures. Importantly, the occurrence of CD74 in the formation of fusion proteins has not been well explored despite the fact that ROS1 and NRG1 families utilize CD74 as the primary partner for the formation of oncogenic fusions. Fusion proteins known to be oncogenic drivers, including those of CD74, are typically detected and targeted after standard chemotherapeutic plans fail and the disease relapses. The analysis reported herein provides insights into the early intervention of CD74 fusions and highlights the need for improved routine assessment methods so that targeted therapies can be applied while they are most effective.

A novel CAR-T cell product targeting CD74 is an effective therapeutic approach in preclinical mantle cell lymphoma models

BACKGROUND

Mantle cell lymphoma (MCL) is a rare B-cell non-Hodgkin lymphoma subtype which remains incurable despite multimodal approach including chemoimmunotherapy followed by stem cell transplant, targeted approaches such as the BTK inhibitor ibrutinib, and CD19 chimeric antigen receptor (CAR) T cells. CD74 is a nonpolymorphic type II integral membrane glycoprotein identified as an MHC class II chaperone and a receptor for macrophage migration inhibitory factor. Our group previously reported on CD74's abundant expression in MCL and its ability to increase via pharmacological inhibition of autophagosomal degradation. Milatuzumab, a fully humanized anti-CD74 monoclonal antibody, demonstrated significant activity in preclinical lymphoma models but failed to provide meaningful benefits in clinical trials mainly due to its short half-life. We hypothesized that targeting CD74 using a CAR-T cell would provide potent and durable anti-MCL activity.

METHODS

We engineered a second generation anti-CD74 CAR with 4-1BB and CD3ζ signaling domains (74bbz). Through in silico and rational mutagenesis on the scFV domain, the 74bbz CAR was functionally optimized for superior antigen binding affinity, proliferative signaling, and cytotoxic activity against MCL cells in vitro and in vivo.

RESULTS

Functionally optimized 74bbz CAR-T cells (clone 42105) induced significant killing of MCL cell lines, and primary MCL patient samples including one relapse after commercial CD19 CAR-T cell therapy with direct correlation between antigen density and cytotoxicity. It significantly prolonged the survival of an animal model established in NOD-SCIDγc-/- (NSG) mice engrafted with a human MCL cell line Mino subcutaneously compared to controls. Finally, while CD74 is also expressed on normal immune cell subsets, treatment with 74bbz CAR-T cells resulted in minimal cytotoxicity against these cells both in vitro and in vivo.

CONCLUSIONS

Targeting CD74 with 74bbz CAR-T cells represents a new cell therapy to provide a potent and durable and anti-MCL activity.

Multicytokine-producing CD4+ T cells characterize the livers of patients with NASH

A role of CD4+ T cells during the progression from nonalcoholic fatty liver disease (NAFLD) to nonalcoholic steatohepatitis (NASH) has been suggested, but which polarization state of these cells characterizes this progression and the development of fibrosis remain unclear. In addition, a gut-liver axis has been suggested to play a role in NASH, but the role of CD4+ T cells in this axis has just begun to be investigated. Combining single-cell RNA sequencing and multiple-parameter flow cytometry, we provide the first cell atlas to our knowledge focused on liver-infiltrating CD4+ T cells in patients with NAFLD and NASH, showing that NASH is characterized by a population of multicytokine-producing CD4+ T cells. Among these cells, only those with a Th17 polarization state were enriched in patients with advanced fibrosis. In parallel, we observed that Bacteroides appeared to be enriched in the intestine of NASH patients and to correlate with the frequency of multicytokine-producing CD4+ T cells. In short, we deliver a CD4+ T cell atlas of NAFLD and NASH, providing the rationale to target CD4+ T cells with a Th17 polarization state to block fibrosis development. Finally, our data offer an early indication to test whether multicytokine-producing CD4+ T cells are part of the gut-liver axis characterizing NASH.

Identification of invariant chain CD74 as a functional receptor of tissue inhibitor of metalloproteinases-1 (TIMP-1)

Multifunctionality of tissue inhibitor of metalloproteinases-1 (TIMP-1) comprising antiproteolytic as well as cytokinic activity has been attributed to its N-terminal and C-terminal domains, respectively. The molecular basis of the emerging proinflammatory cytokinic activity of TIMP-1 is still not completely understood. The cytokine receptor invariant chain (CD74) is involved in many inflammation-associated diseases and is highly expressed by immune cells. CD74 triggers zeta chain–associated protein kinase-70 (ZAP-70) signaling–associated activation upon interaction with its only known ligand, the macrophage migration inhibitory factor. Here, we demonstrate TIMP-1–CD74 interaction by coimmunoprecipitation and confocal microscopy in cells engineered to overexpress CD74. In silico docking in HADDOCK predicted regions of the N-terminal domain of TIMP-1 (N-TIMP-1) to interact with CD74. This was experimentally confirmed by confocal microscopy demonstrating that recombinant N-TIMP-1 lacking the entire C-terminal domain was sufficient to bind CD74. Interaction of TIMP-1 with endogenously expressed CD74 was demonstrated in the Namalwa B lymphoma cell line by dot blot binding assays as well as confocal microscopy. Functionally, we demonstrated that TIMP-1–CD74 interaction triggered intracellular ZAP-70 activation. N-TIMP-1 was sufficient to induce ZAP-70 activation and interference with the cytokine-binding site of CD74 using a synthetic peptide–abrogated TIMP-1-mediated ZAP-70 activation. Altogether, we here identified CD74 as a receptor and mediator of cytokinic TIMP-1 activity and revealed TIMP-1 as moonlighting protein harboring both cytokinic and antiproteolytic activity within its N-terminal domain. Recognition of this functional TIMP-1–CD74 interaction may shed new light on clinical attempts to therapeutically target ligand-induced CD74 activity in cancer and other inflammatory diseases.

Emerging therapies in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a rare, B cell non-Hodgkin's lymphoma with highly heterogeneous clinical presentation and aggressiveness. First-line treatment consists of intensive chemotherapy with autologous stem cell transplant for the fit, transplant eligible patients, or less intensive chemotherapy for the less fit (and transplant-ineligible) patients. Patients eventually relapse with a progressive clinical course. Numerous therapeutic approaches have emerged over the last few years which have significantly changed the treatment landscape of MCL. These therapies consist of targeted approaches such as BTK and BCL2 inhibitors that provide durable therapeutic responses. However, the optimum combination and sequencing of these therapies is unclear and is currently investigated in several ongoing studies. Furthermore, cellular therapies such as chimeric antigen receptor (CAR) T cells and bispecific T cell engager (BiTe) antibodies have shown impressive results and will likely shape treatment approaches in relapsed MCL, especially after failure with BTK inhibitors. Herein, we provide a comprehensive review of past and ongoing studies that will likely significantly impact our approach to MCL treatment in both the frontline (for transplant eligible and ineligible patients) as well as in the relapsed setting. We present the most up to date results from these studies as well as perspectives on future studies in MCL.

The Expanding Field of Secondary Antibody Deficiency: Causes, Diagnosis, and Management

Antibody deficiency or hypogammaglobulinemia can have primary or secondary etiologies. Primary antibody deficiency (PAD) is the result of intrinsic genetic defects, whereas secondary antibody deficiency may arise as a consequence of underlying conditions or medication use. On a global level, malnutrition, HIV, and malaria are major causes of secondary immunodeficiency. In this review we consider secondary antibody deficiency, for which common causes include hematological malignancies, such as chronic lymphocytic leukemia or multiple myeloma, and their treatment, protein-losing states, and side effects of a number of immunosuppressive agents and procedures involved in solid organ transplantation. Secondary antibody deficiency is not only much more common than PAD, but is also being increasingly recognized with the wider and more prolonged use of a growing list of agents targeting B cells. SAD may thus present to a broad range of specialties and is associated with an increased risk of infection. Early diagnosis and intervention is key to avoiding morbidity and mortality. Optimizing treatment requires careful clinical and laboratory assessment and may involve close monitoring of risk parameters, vaccination, antibiotic strategies, and in some patients, immunoglobulin replacement therapy (IgRT). This review discusses the rapidly evolving list of underlying causes of secondary antibody deficiency, specifically focusing on therapies targeting B cells, alongside recent advances in screening, biomarkers of risk for the development of secondary antibody deficiency, diagnosis, monitoring, and management.

Macrophage migration inhibitory factor regulates mitochondrial dynamics and cell growth of human cancer cell lines through CD74-NF-κB signaling

The indispensable role of macrophage migration inhibitory factor (MIF) in cancer cell proliferation is unambiguous, although which specific roles the cytokine plays to block apoptosis by preserving cell growth is still obscure. Using different cancer cell lines (AGS, HepG2, HCT116, and HeLa), here we report that the silencing of MIF severely deregulated mitochondrial structural dynamics by shifting the balance toward excess fission, besides inducing apoptosis with increasing sub-G₀ cells. Furthermore, enhanced mitochondrial Bax translocation along with cytochrome c release, down-regulation of Bcl-xL, and Bcl-2 as well as up-regulation of Bad, Bax, and p53 indicated the activation of a mitochondrial pathway of apoptosis upon MIF silencing. The data also indicate a concerted down-regulation of Opa1 and Mfn1 along with a significant elevation of Drp1, cumulatively causing mitochondrial fragmentation upon MIF silencing. Up-regulation of Drp1 was found to be further coupled with fissogenic serine 616 phosphorylation and serine 637 dephosphorylation, thus ensuring enhanced mitochondrial translocation. Interestingly, MIF silencing was found to be associated with decreased NF-κB activation. In fact, NF-κB knockdown in turn increased mitochondrial fission and cell death. In addition, the silencing of CD74, the cognate receptor of MIF, remarkably increased mitochondrial fragmentation in addition to preventing cell proliferation, inducing mitochondrial depolarization, and increasing apoptotic cell death. This indicates the active operation of a MIF-regulated CD74-NF-κB signaling axis for maintaining mitochondrial stability and cell growth. Thus, we propose that MIF, through CD74, constitutively activates NF-κB to control mitochondrial dynamics and stability for promoting carcinogenesis via averting apoptosis.

High frequency of CD74 expression in lymphomas: implications for targeted therapy using a novel anti-CD74-drug conjugate

CD74 is a type II transmembrane glycoprotein that functions as an MHC class II chaperone and displays diverse roles in immune responses. Recently, anti‐CD74 immunotherapy has shown promise as an effective treatment strategy for lymphoid neoplasms in preclinical models. Using a human anti‐CD74 antibody (SP7219), we defined the expression of CD74 protein in both normal and over 790 neoplastic hematolymphoid tissue samples. We found that CD74 is expressed broadly in normal B‐cell compartments including primary and secondary lymphoid follicles and in the thymic medulla. The vast majority of lymphomas expressed CD74, including Hodgkin lymphomas (98%), B‐cell lymphomas (96%), extranodal NK/T‐cell lymphomas (88%), mature T‐cell lymphomas (80%), and plasma cell myeloma (75%). Our findings confirm and expand previous observations regarding the expression of CD74 and suggest that CD74 expression on tumor cells may be directly targeted for immunomodulatory therapy for lymphoid and plasma cell malignancies.

TWEAK increases CD74 expression and sensitizes to DDT proinflammatory actions in tubular cells

CD74 is a multifunctional protein and a receptor for Macrophage Migration Inhibitory Factor (MIF) and MIF-2 / D-dopachrome tautomerase (DDT) cytokines, upregulated in diabetic kidney disease. However, the drivers of CD74 expression and DDT function in kidney cells are poorly characterized. TWEAK is a proinflammatory cytokine that promotes kidney injury. We have now identified CD74 gene expression as upregulated in the kidneys in response to systemic TWEAK administration in mice, and have characterized the in vivo CD74 expression and the functional consequences in cultured cells. TWEAK administration to mice resulted in a progressive time-dependent (up to 24h) upregulation of kidney CD74 mRNA (RT-PCR) and protein (Western blot). Furthermore, the CD74 ligands MIF and DDT were also upregulated at the protein level 24h after TWEAK administration. Immunohistochemistry localized the increased CD74, MIF and DDT expression to tubular cells. In cultured tubular cells, TWEAK increased CD74 mRNA and protein expression dose-dependently, with a temporal pattern similar to in vivo. TWEAK-induced CD74 localized to the cell membrane, where it can function as a cytokine receptor. For the first time, we explored the actions of DDT in tubular cells and found that DDT amplified the increase in MCP-1 and RANTES expression in response to TWEAK. By contrast, DDT did not significantly modify TWEAK-induced Klotho downregulation. In conclusion, TWEAK upregulates CD74 and its ligands MIF and DDT in renal tubular cells. This may have functional consequences for kidney injury since DDT amplified the inflammatory response to TWEAK.

Pathogenic role for macrophage migration inhibitory factor in glioblastoma and its targeting with specific inhibitors as novel tailored therapeutic approach

Macrophage Migration Inhibitory Factor (MIF) is a pro-inflammatory cytokine expressed by a variety of cell types. Although MIF has been primarily studied for its role in the pathogenesis of autoimmune diseases, it has also been shown to promote tumorigenesis and it is over expressed in various malignant tumors. MIF is able to induce angiogenesis, cell cycle progression, and to block apoptosis. As tailored therapeutic approaches for the inhibition of endogenous MIF are being developed, it is important to evaluate the role of MIF in individual neoplastic conditions that may benefit from specific MIF inhibitors. Along with this line, in this paper, we have reviewed the evidence of the involvement of MIF in the etiopathogenesis and progression of glioblastoma and the preclinical data suggesting the possible use of specific MIF inhibition as a potential novel therapeutic strategy for brain tumors.

Novel half-life extended anti-MIF nanobodies protect against endotoxic shock

Sepsis-leading to septic shock-is the leading cause of death in intensive care units. The systemic inflammatory response to infection, which is initiated by activated myeloid cells, plays a key role in the lethal outcome. Macrophage migration inhibitory factor (MIF) is an upstream immunoregulatory mediator, released by myeloid cells, that underlies a common genetic susceptibility to different infections and septic shock. Accordingly, strategies that are aimed at inhibiting the action of MIF have therapeutic potential. Here, we report the isolation and characterization of tailorable, small, affinity-matured nanobodies (Nbs; single-domain antigen-binding fragments derived from camelid heavy-chain Abs) directed against MIF. Of importance, these bioengineered Nbs bind both human and mouse MIFs with nanomolar affinity. NbE5 and NbE10 inhibit key MIF functions that can exacerbate septic shock, such as the tautomerase activity of MIF (by blocking catalytic pocket residues that are critical for MIF's conformation and receptor binding), the TNF-inducing potential, and the ability of MIF to antagonize glucocorticoid action. A lead NbE10, tailored to be a multivalent, half-life extended construct (NbE10-NbAlb8-NbE10), attenuated lethality in murine endotoxemia when administered via single injection, either prophylactically or therapeutically. Hence, Nbs, with their structural and pharmacologic advantages over currently available inhibitors, may be an effective, novel approach to interfere with the action of MIF in septic shock and other conditions of inflammatory end-organ damage.-Sparkes, A., De Baetselier, P., Brys, L., Cabrito, I., Sterckx, Y. G.-J., Schoonooghe, S., Muyldermans, S., Raes, G., Bucala, R., Vanlandschoot, P., Van Ginderachter, J. A., Stijlemans, B. Novel half-life extended anti-MIF nanobodies protect against endotoxic shock.

CD74 Deficiency Mitigates Systemic Lupus Erythematosus-like Autoimmunity and Pathological Findings in Mice

CD74 mediates MHC class-II antigenic peptide loading and presentation and plays an important role in the pathogenesis of autoimmune diseases, including systemic lupus erythematosus. C57BL/6 Fas^lpr mice that develop spontaneous lupus-like autoimmunity and pathology showed elevated CD74 expression in the inflammatory cell infiltrates and the adjacent tubular epithelial cells (TECs) in kidneys affected by lupus nephritis but negligible levels in kidneys from age-matched wild-type mice. The inflammatory cytokine IFN-γ or IL-6 induced CD74 expression in kidney TECs in vitro. The presence of kidney TECs from Fas^lpr mice, rather than from wild-type mice, produced significantly stronger histones, dsDNA, and ribonucleoprotein-Smith Ag complex-induced CD4⁺ T cell activation. Splenocytes from CD74-deficient Fas^lprCd74^-/- mice had muted responses in a MLR and to the autoantigen histones. Compared with Fas^lprCd74^+/+ mice, Fas^lprCd74^-/- mice had reduced kidney and spleen sizes, splenic activated T cells and B cells, serum IgG and autoantibodies, urine albumin/creatinine ratio, kidney Periodic acid-Schiff score, IgG and C3 deposition, and serum IL-6 and IL-17A levels, but serum IL-2 and TGF-β levels were increased. Study of chronic graft-versus-host C57BL/6 mice that received donor splenocytes from B6.C-H2^bm12 /KhEg mice and those that received syngeneic donor splenocytes yielded similar observations. CD74 deficiency reduced lupus-like autoimmunity and kidney pathology in chronic graft-versus-host mice. This investigation establishes the direct participation of CD74 in autoimmunity and highlights a potential role for CD74 in kidney TECs, together with professional APCs in systemic lupus erythematosus.

HLA class I-restricted MYD88 L265P-derived peptides as specific targets for lymphoma immunotherapy

Genome sequencing has uncovered an array of recurring somatic mutations in different non-Hodgkin lymphoma (NHL) subtypes. If affecting protein-coding regions, such mutations may yield mutation-derived peptides that may be presented by HLA class I proteins and recognized by cytotoxic T cells. A recurring somatic and oncogenic driver mutation of the Toll-like receptor adaptor protein MYD88, Leu265Pro (L265P) was identified in up to 90% of different NHL subtype patients. We therefore screened the potential of MYD88L265P-derived peptides to elicit cytotoxic T cell responses as tumor-specific neoantigens. Based on in silico predictions, we identified potential MYD88L265P-containing HLA ligands for several HLA class I restrictions. A set of HLA class I MYD88L265P-derived ligands elicited specific cytotoxic T cell responses for HLA-B*07 and -B*15. These data highlight the potential of MYD88L265P mutation-specific peptide-based immunotherapy as a novel personalized treatment approach for patients with MYD88L265P+ NHLs that may complement pharmacological approaches targeting oncogenic MyD88 L265P signaling.

CD74 in Kidney Disease

CD74 (invariant MHC class II) regulates protein trafficking and is a receptor for macrophage migration inhibitory factor (MIF) and d-dopachrome tautomerase (d-DT/MIF-2). CD74 expression is increased in tubular cells and/or glomerular podocytes and parietal cells in human metabolic nephropathies, polycystic kidney disease, graft rejection and kidney cancer and in experimental diabetic nephropathy and glomerulonephritis. Stressors like abnormal metabolite (glucose, lyso-Gb3) levels and inflammatory cytokines increase kidney cell CD74. MIF activates CD74 to increase inflammatory cytokines in podocytes and tubular cells and proliferation in glomerular parietal epithelial cells and cyst cells. MIF overexpression promotes while MIF targeting protects from experimental glomerular injury and kidney cysts, and interference with MIF/CD74 signaling or CD74 deficiency protected from crescentic glomerulonephritis. However, CD74 may protect from interstitial kidney fibrosis. Furthermore, CD74 expression by stressed kidney cells raises questions about the kidney safety of cancer therapy strategies delivering lethal immunoconjugates to CD74-expressing cells. Thus, understanding CD74 biology in kidney cells is relevant for kidney therapeutics.