CAR T Cells Targeting Podoplanin Reduce Orthotopic Glioblastomas in Mouse Brains

Expand available targets for CAR-T therapy to overcome tumor drug resistance based on the "Evolutionary Traps"

Based on the concept of "Evolutionary Traps", targeting survival essential genes obtained during tumor drug resistance can effectively eliminate resistant cells. While, it still faces limitations. In this study, lapatinib-resistant cells were used to test the concept of "Evolutionary Traps" and no suitable target stand out because of the identified genes without accessible drug. However, a membrane protein PDPN, which is low or non-expressed in normal tissues, is identified as highly expressed in lapatinib-resistant tumor cells. PDPN CAR-T cells were developed and showed high cytotoxicity against lapatinib-resistant tumor cells in vitro and in vivo, suggesting that CAR-T may be a feasible route for overcoming drug resistance of tumor based on "Evolutionary Trap". To test whether this concept is cell line or drug dependent, we analyzed 21 drug-resistant tumor cell expression profiles reveal that JAG1, GPC3, and L1CAM, which are suitable targets for CAR-T treatment, are significantly upregulated in various drug-resistant tumor cells. Our findings shed light on the feasibility of utilizing CAR-T therapy to treat drug-resistant tumors and broaden the concept of the "Evolutionary Trap".

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Development of a Sensitive Anti-Mouse CD39 Monoclonal Antibody (C39Mab-1) for Flow Cytometry and Western Blot Analyses

CD39 is involved in adenosine metabolism by converting extracellular ATP to adenosine. As extracellular adenosine plays a critical role in the immune suppression of the tumor microenvironment, the inhibition of CD39 activity by monoclonal antibodies (mAbs) is one of the important strategies for tumor therapy. This study developed specific and sensitive mAbs for mouse CD39 (mCD39) using the Cell-Based Immunization and Screening method. The established anti-mCD39 mAb, C39Mab-1 (rat IgG2a, kappa), reacted with mCD39-overexpressed Chinese hamster ovary-K1 (CHO/mCD39) by flow cytometry. The kinetic analysis using flow cytometry indicated that the dissociation constant of C39Mab-1 for CHO/mCD39 was 7.3 × 10-9 M. Furthermore, C39Mab-1 detected the lysate of CHO/mCD39 by western blot analysis. These results indicated that C39Mab-1 is useful for the detection of mCD39 in many functional studies.

Establishment of Anti-Dog Programmed Cell Death Ligand 1 Monoclonal Antibodies for Immunohistochemistry

Immune checkpoint blockade therapy has shown successful clinical outcomes in multiple human cancers. In dogs, several types of tumors resemble human tumors in many respects. Therefore, several groups have developed the anti-dog programmed cell death ligand 1 (dPD-L1) monoclonal antibodies (mAbs) and showed efficacy in several canine tumors. To examine the abundance of dPD-L1 in canine tumors, anti-dPD-L1 diagnostic mAbs for immunohistochemistry are required. In this study, we immunized the peptide in the dPD-L1 intracellular domain, and established anti-dPD-L1 mAbs, L1Mab-352 (mouse IgG1, kappa), and L1Mab-354 (mouse IgG1, kappa). In enzyme-linked immunosorbent assay, L1Mab-352 and L1Mab-354 showed high-binding affinity to the dPD-L1 peptide, and the dissociation constants (KD) were determined as 6.9 × 10-10 M and 7.2 × 10-10 M, respectively. Furthermore, L1Mab-352 and L1Mab-354 were applicable for the detection of dPD-L1 in immunohistochemical analysis in paraffin-embedded dPD-L1-overexpressed cells. These results indicated that L1Mab-352 and L1Mab-354 are useful for detecting dPD-L1 in immunohistochemical analysis.

Antitumor activities against breast cancers by an afucosylated anti-HER2 monoclonal antibody H2 Mab-77-mG2a -f

Breast cancer patients with high levels of human epidermal growth factor receptor 2 (HER2) expression have worse clinical outcomes. Anti-HER2 monoclonal antibody (mAb) is the most important therapeutic modality for HER2-positive breast cancer. We previously immunized mice with the ectodomain of HER2 to create the anti-HER2 mAb, H2 Mab-77 (mouse IgG1 , kappa). This was then altered to produce H2 Mab-77-mG2a -f, an afucosylated mouse IgG2a . In the present work, we examined the reactivity of H2 Mab-77-mG2a -f and antitumor effects against breast cancers in vitro and in vivo. BT-474, an endogenously HER2-expressing breast cancer cell line, was identified by H2 Mab-77-mG2a -f with a strong binding affinity (a dissociation constant [KD ]: 5.0 × 10-9  M). H2 Mab-77-mG2a -f could stain HER2 of breast cancer tissues in immunohistochemistry and detect HER2 protein in Western blot analysis. Furthermore, H2 Mab-77-mG2a -f demonstrated strong antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) for BT-474 cells. MDA-MB-468, a HER2-negative breast cancer cell line, was unaffected by H2 Mab-77-mG2a -f. Additionally, in the BT-474-bearing tumor xenograft model, H2 Mab-77-mG2a -f substantially suppressed tumor development when compared with the control mouse IgG2a mAb. In contrast, the HER2-negative MDA-MB-468-bearing tumor xenograft model showed no response to H2 Mab-77-mG2a -f. These findings point to the possibility of H2 Mab-77-mG2a -f as a treatment regimen by showing that it has antitumor effects on HER2-positive breast tumors.

Near-infrared-II Ag2S quantum dot probes targeting podoplanin enhance immunotherapy in oral squamous cell carcinoma

Partial epithelial-mesenchymal transition (pEMT) plays a vital role in oral squamous cell carcinoma (OSCC) cervical lymph node metastasis and tumor immune escape as an immune barrier. However, targeted interventions for pEMT have yet to be established. In this study, we generated an αPDPN-Ag2S probe by modifying a Podoplanin(PDPN) monoclonal antibody on the surface of near infrared (NIR)-II Ag2S quantum dots (QDs) with carboxyl groups through an amide reaction. Then, we evaluated its in vivo targeting ability, therapeutic efficacy of eliminating pEMT using αPDPN-Ag2S-mediated NIR-II photoimmunotherapy (PIT) and biological safety. Here, we found that pEMT is related to CD8 + T-cell infiltration in our human OSCC tissue microarray. Compared with PdpnWT SCC7, the slower growth rate of subcutaneous graft tumors implanted with PdpnKD SCC7 was associated with a change in the tumor immune microenvironment (TIM) in an immunocompetent C3H/HeJ mouse model. In vitro, αPDPN-Ag2S plus NIR 808 nm laser irradiation induced SCC7 cell death. In vivo, NIR-II imaging results show that the αPDPN-Ag2S probe has a good active-targeting ability in a 4-nitroquinoline 1-oxide (4NQO)-induced C57 mouse OSCC model and C3H/HeJ SCC7 subcutaneous graft tumor model. Elimination of pEMT cells by NIR-II αPDPN-Ag2S probe-mediated PIT significantly reversed the local immunosuppressive tumor microenvironment and enhanced PD-1 immunotherapy efficacy. The safety profiles of αPDPN-Ag2S in BALB/c mice were also acceptable. Thus, αPDPN-Ag2S has important clinical translational value in predicting the risk of cervical lymph node metastasis. Importantly, our study proposed a new way to improve the efficacy of tumor immunotherapy.

The role of podoplanin inhibitors in controlling oral cancer progression

OBJECTIVE

In this article, we review the current studies on the role of podoplanin in oral cancer and the potential application of podoplanin inhibitors as a therapeutic agent for oral cancer.

DESIGN

The narrative review approach was conducted, providing a comprehensive perspective of related literature. Publications addressing podoplanin and its inhibitors in the context of oral cancer were retrieved from PubMed and Scopus databases.

RESULTS

Podoplanin has emerged as a biomarker and therapeutic agent for oral cancer. Numerous studies have reported high podoplanin expression in oral cancer and pre-cancerous lesions compared to normal cells. A specific inhibitor targeting podoplanin may have the potential to prevent oral carcinogenesis via interfering with the pathway of cancerous cells involved in cell proliferation and metastasis. Antibodies, chimeric antigen receptor (CAR)-T cells, cancer-specific mAb (CasMab), synthetic molecules, and lectins are among the materials used as anticancer agents targeting podoplanin. Plant-derived lectins appear to demonstrate a unique advantage against alternative candidates.

CONCLUSIONS

The use of podoplanin inhibitors in place of existing therapeutic approaches could be a promising and novel approach to the prevention and treatment of oral cancer. Nevertheless, further research is required to investigate the practical application of such inhibitors.

A Rat Anti-Mouse CD39 Monoclonal Antibody for Flow Cytometry

By converting extracellular adenosine triphosphate to adenosine, CD39 is involved in adenosine metabolism. The extracellular adenosine plays a critical role in the immune suppression of the tumor microenvironment. Therefore, the inhibition of CD39 activity by monoclonal antibodies (mAbs) is thought to be one of the important strategies for tumor therapy. In this study, we developed novel mAbs for mouse CD39 (mCD39) using the Cell-Based Immunization and Screening (CBIS) method. One of the established anti-mCD39 mAbs, C39Mab-2 (rat IgG2a, lambda), reacted with mCD39-overexpressed Chinese hamster ovary-K1 (CHO/mCD39) and an endogenously mCD39-expressed cell line (SN36) by flow cytometry. The kinetic analysis using flow cytometry indicated that the dissociation constant (KD) values of C39Mab-2 for CHO/mCD39 and SN36 were 5.5 × 10-9 M and 4.9 × 10-9 M, respectively. These results indicated that C39Mab-2 is useful for the detection of mCD39 in flow cytometry.

Defucosylated Monoclonal Antibody (H2Mab-139-mG2a-f) Exerted Antitumor Activities in Mouse Xenograft Models of Breast Cancers against Human Epidermal Growth Factor Receptor 2

The clinically approved human epidermal growth factor receptor 2 (HER2)-targeting monoclonal antibodies (mAbs), trastuzumab, and pertuzumab, target domains IV and II, respectively. Trastuzumab is now the standard treatment for HER2-overexpressed breast and gastric cancers, and trastuzumab in combination with pertuzumab showed clinical benefit. However, there still exist patients who do not respond to the therapy. Furthermore, HER2 mutants that cannot be recognized by pertuzumab were found in tumors. Therefore, novel anti-HER2 mAbs and modalities have been desired. In our previous study, we developed a novel anti-HER2 domain I mAb, H2Mab-139 (mouse IgG1, kappa). We herein produced a defucosylated mouse IgG2a type of mAb against HER2 (H2Mab-139-mG2a-f) to enhance antibody-dependent cellular cytotoxicity (ADCC)-mediated antitumor activity. H2Mab-139-mG2a-f exhibits a high binding affinity in flow cytometry with the dissociation constant (KD) determined to be 3.9 × 10-9 M and 7.7 × 10-9 M against HER2-overexpressed Chinese hamster ovary (CHO)-K1 (CHO/HER2) and HER2-positive BT-474 cells, respectively. Moreover, we showed that H2Mab-139-mG2a-f exerted ADCC and complement-dependent cytotoxicity against CHO/HER2 and BT-474 in vitro and exhibited potent antitumor activities in mouse xenograft models. These results indicated that H2Mab-139-mG2a-f exerts antitumor effects against HER2-positive human breast cancers and is useful as an antibody treatment for HER2-positive human cancers.

Bispecific T-Cell Engagers and Chimeric Antigen Receptor T-Cell Therapies in Glioblastoma: An Update

Glioblastoma is the most common malignant primary brain tumor in adults. The prognosis is extremely poor even with standard treatment of maximal safe resection, radiotherapy, and chemotherapy. Recurrence is inevitable within months, and treatment options are very limited. Chimeric antigen receptor T-cell therapy (CART) and bispecific T-cell engagers (TCEs) are two emerging immunotherapies that can redirect T-cells for tumor-specific killing and have shown remarkable success in hematological malignancies and been under extensive study for application in glioblastoma. While there have been multiple clinical trials showing preliminary evidence of safety and efficacy for CART, bispecific TCEs are still in the early stages of clinical testing, with preclinical studies showing very promising results. However, there are multiple shared challenges that need to be addressed in the future, including the route of delivery, antigen escape, the immunosuppressive tumor microenvironment, and toxicity resulting from the limited choice of tumor-specific antigens. Efforts are underway to optimize the design of both these treatments and find the ideal combination therapy to overcome these challenges. In this review, we describe the work that has been performed as well as novel approaches in glioblastoma and in other solid tumors that may be applicable in the future.

EMab-300 Detects Mouse Epidermal Growth Factor Receptor-Expressing Cancer Cell Lines in Flow Cytometry

Epidermal Growth Factor Receptor (EGFR) overexpression or its mutation mediates the sustaining proliferative signaling, which is an important hallmark of cancer. Human EGFR-targeting monoclonal antibody (mAb) therapy such as cetuximab has been approved for clinical use in patients with colorectal cancers and head and neck squamous cell carcinomas. A reliable preclinical mouse model is essential to further develop the mAb therapy against EGFR. Therefore, sensitive mAbs against mouse EGFR (mEGFR) should be established. In this study, we developed a specific and sensitive mAb for mEGFR using the Cell-Based Immunization and Screening (CBIS) method. The established anti-mEGFR mAb, EMab-300 (rat IgG₁, kappa), reacted with mEGFR-overexpressed Chinese hamster ovary-K1 (CHO/mEGFR) and endogenously mEGFR-expressed cell lines, including NMuMG (a mouse mammary gland epithelial cell) and Lewis lung carcinoma cells, using flow cytometry. The kinetic analysis using flow cytometry indicated that the K_D of EMab-300 for CHO/mEGFR and NMuMG was 4.3 × 10^-8 M and 1.9 × 10^-8 M, respectively. These results indicated that EMab-300 applies to the detection of mEGFR using flow cytometry and may be useful to obtain the proof of concept in preclinical studies.

Establishment of a Novel Anti-CD44 Variant 10 Monoclonal Antibody C44Mab-18 for Immunohistochemical Analysis against Oral Squamous Cell Carcinomas

Head and neck squamous cell carcinoma (HNSCC) is the most common type of head and neck cancer, and has been revealed as the second-highest expression of CD44 in cancers. CD44 has been investigated as a cancer stem cell marker of HNSCC and plays a critical role in tumor malignant progression. Especially, splicing variant isoforms of CD44 (CD44v) are overexpressed in cancers and considered a promising target for cancer diagnosis and therapy. We developed monoclonal antibodies (mAbs) against CD44 by immunizing mice with CD44v3-10-overexpressed PANC-1 cells. Among the established clones, C₄₄Mab-18 (IgM, kappa) reacted with CHO/CD44v3-10, but not with CHO/CD44s and parental CHO-K1 using flow cytometry. The epitope mapping using peptides that cover variant exon-encoded regions revealed that C₄₄Mab-18 recognized the border sequence between variant 10 and the constant exon 16-encoded sequence. These results suggest that C₄₄Mab-18 recognizes variant 10-containing CD44v, but not CD44s. Furthermore, C₄₄Mab-18 could recognize the human oral squamous cell carcinoma (OSCC) cell line, HSC-3, in flow cytometry. The apparent dissociation constant (K_D) of C₄₄Mab-18 for CHO/CD44v3-10 and HSC-3 was 1.6 × 10^-7 M and 1.7 × 10^-7 M, respectively. Furthermore, C₄₄Mab-18 detected CD44v3-10 but not CHO/CD44s in Western blotting, and endogenous CD44v10 in immunohistochemistry using OSCC tissues. These results indicate that C₄₄Mab-18 is useful for detecting CD44v10 in flow cytometry and immunohistochemistry.

A Novel Anti-CD44 Variant 3 Monoclonal Antibody C44Mab-6 Was Established for Multiple Applications

Cluster of differentiation 44 (CD44) promotes tumor progression through the recruitment of growth factors and the acquisition of stemness, invasiveness, and drug resistance. CD44 has multiple isoforms including CD44 standard (CD44s) and CD44 variants (CD44v), which have common and unique functions in tumor development. Therefore, elucidating the function of each CD44 isoform in a tumor is essential for the establishment of CD44-targeting tumor therapy. We have established various anti-CD44s and anti-CD44v monoclonal antibodies (mAbs) through the immunization of CD44v3-10-overexpressed cells. In this study, we established C₄₄Mab-6 (IgG₁, kappa), which recognized the CD44 variant 3-encoded region (CD44v3), as determined via an enzyme-linked immunosorbent assay. C₄₄Mab-6 reacted with CD44v3-10-overexpressed Chinese hamster ovary (CHO)-K1 cells (CHO/CD44v3-10) or some cancer cell lines (COLO205 and HSC-3) via flow cytometry. The apparent K_D of C₄₄Mab-6 for CHO/CD44v3-10, COLO205, and HSC-3 was 1.5 × 10^-9 M, 6.3 × 10^-9 M, and 1.9 × 10^-9 M, respectively. C₄₄Mab-6 could detect the CD44v3-10 in Western blotting and stained the formalin-fixed paraffin-embedded tumor sections in immunohistochemistry. These results indicate that C₄₄Mab-6 is useful for detecting CD44v3 in various experiments and is expected for the application of tumor diagnosis and therapy.

Overexpression of Podoplanin Predicts Poor Prognosis in Patients With Glioma

High podoplanin (PDPN) expression correlates with poor prognosis in various cancers. However, the expression and clinical value of PDPN in glioma are unclear. In this study, PDPN expression was compared in 227 glioma tissues and 22 paired non-neoplastic tissues, and its association with prognostic factors was statistically analyzed. The effect of PDPN knockdown on the proliferation ability of glioma cells (U87MG and U118MG cell lines) was assessed along with the underlying molecular mechanism. Overexpression of PDPN was observed in the majority of glioma tissues compared with the expression in normal tissues. PDPN overexpression was positively correlated with IDH wild-type status, TERT promoter mutation status, and ATRX retention status, and was negatively correlated with 1p/19q codeletion status. The expression level of PDPN was positively correlated with the glioma grade in the diffuse astrocytoma, IDH wild-type. High PDPN expression was also negatively correlated with survival in astrocytoma patients with IDH mutation or wild-type and in glioblastoma patients with IDH wild-type. Grade, radiochemotherapy, and PDPN overexpression emerged as independent indicators for a poor prognosis of glioma patients. PDPN knockdown suppressed proliferation and reduced p-Akt and p-mTOR protein expression in glioma cells. PDPN is a potential biomarker or therapeutic target for glioma that is closely associated with tumor grade and poor prognosis, which may play a role in enhancing cell proliferation via Akt/mTOR signaling.

Development of a Novel Anti-CD44 Variant 5 Monoclonal Antibody C44Mab-3 for Multiple Applications against Pancreatic Carcinomas

Pancreatic cancer exhibits a poor prognosis due to the lack of early diagnostic biomarkers and the resistance to conventional chemotherapy. CD44 has been known as a cancer stem cell marker and plays tumor promotion and drug resistance roles in various cancers. In particular, the splicing variants are overexpressed in many carcinomas and play essential roles in the cancer stemness, invasiveness or metastasis, and resistance to treatments. Therefore, the understanding of each CD44 variant's (CD44v) function and distribution in carcinomas is essential for the establishment of CD44-targeting tumor therapy. In this study, we immunized mice with CD44v3-10-overexpressed Chinese hamster ovary (CHO)-K1 cells and established various anti-CD44 monoclonal antibodies (mAbs). One of the established clones (C₄₄Mab-3; IgG₁, kappa) recognized peptides of the variant-5-encoded region, indicating that C₄₄Mab-3 is a specific mAb for CD44v5. Moreover, C₄₄Mab-3 reacted with CHO/CD44v3-10 cells or pancreatic cancer cell lines (PK-1 and PK-8) by flow cytometry. The apparent K_D of C₄₄Mab-3 for CHO/CD44v3-10 and PK-1 was 1.3 × 10^-9 M and 2.6 × 10^-9 M, respectively. C₄₄Mab-3 could detect the exogenous CD44v3-10 and endogenous CD44v5 in Western blotting and stained the formalin-fixed paraffin-embedded pancreatic cancer cells but not normal pancreatic epithelial cells in immunohistochemistry. These results indicate that C₄₄Mab-3 is useful for detecting CD44v5 in various applications and is expected to be useful for the application of pancreatic cancer diagnosis and therapy.

A Novel Anti-CD44 Variant 9 Monoclonal Antibody C44Mab-1 Was Developed for Immunohistochemical Analyses against Colorectal Cancers

Cluster of differentiation 44 (CD44) is a type I transmembrane glycoprotein and has been shown to be a cell surface marker of cancer stem-like cells in various cancers. In particular, the splicing variants of CD44 (CD44v) are overexpressed in cancers and play critical roles in cancer stemness, invasiveness, and resistance to chemotherapy and radiotherapy. Therefore, the understanding of the function of each CD44v is indispensable for CD44-targeting therapy. CD44v9 contains the variant 9-encoded region, and its expression predicts poor prognosis in patients with various cancers. CD44v9 plays critical roles in the malignant progression of tumors. Therefore, CD44v9 is a promising target for cancer diagnosis and therapy. Here, we developed sensitive and specific monoclonal antibodies (mAbs) against CD44 by immunizing mice with CD44v3-10-overexpressed Chinese hamster ovary-K1 (CHO/CD44v3-10) cells. We first determined their critical epitopes using enzyme-linked immunosorbent assay and characterized their applications as flow cytometry, western blotting, and immunohistochemistry. One of the established clones, C₄₄Mab-1 (IgG₁, kappa), reacted with a peptide of the variant 9-encoded region, indicating that C₄₄Mab-1 recognizes CD44v9. C₄₄Mab-1 could recognize CHO/CD44v3-10 cells or colorectal cancer cell lines (COLO201 and COLO205) in flow cytometric analysis. The apparent dissociation constant (K_D) of C₄₄Mab-1 for CHO/CD44v3-10, COLO201, and COLO205 was 2.5 × 10^-8 M, 3.3 × 10^-8 M, and 6.5 × 10^-8 M, respectively. Furthermore, C₄₄Mab-1 was able to detect the CD44v3-10 in western blotting and the endogenous CD44v9 in immunohistochemistry using colorectal cancer tissues. These results indicated that C₄₄Mab-1 is useful for detecting CD44v9 not only in flow cytometry or western blotting but also in immunohistochemistry against colorectal cancers.

Development of a Novel Anti-CD44 Variant 7/8 Monoclonal Antibody, C44Mab-34, for Multiple Applications against Oral Carcinomas

Cluster of differentiation 44 (CD44) has been investigated as a cancer stem cell (CSC) marker as it plays critical roles in tumor malignant progression. The splicing variants are overexpressed in many carcinomas, especially squamous cell carcinomas, and play critical roles in the promotion of tumor metastasis, the acquisition of CSC properties, and resistance to treatments. Therefore, each CD44 variant (CD44v) function and distribution in carcinomas should be clarified for the establishment of novel tumor diagnosis and therapy. In this study, we immunized mouse with a CD44 variant (CD44v3–10) ectodomain and established various anti-CD44 monoclonal antibodies (mAbs). One of the established clones (C44Mab-34; IgG1, kappa) recognized a peptide that covers both variant 7- and variant 8-encoded regions, indicating that C44Mab-34 is a specific mAb for CD44v7/8. Moreover, C44Mab-34 reacted with CD44v3–10-overexpressed Chinese hamster ovary-K1 (CHO) cells or the oral squamous cell carcinoma (OSCC) cell line (HSC-3) by flow cytometry. The apparent KD of C44Mab-34 for CHO/CD44v3–10 and HSC-3 was 1.4 × 10−9 and 3.2 × 10−9 M, respectively. C44Mab-34 could detect CD44v3–10 in Western blotting and stained the formalin-fixed paraffin-embedded OSCC in immunohistochemistry. These results indicate that C44Mab-34 is useful for detecting CD44v7/8 in various applications and is expected to be useful in the application of OSCC diagnosis and therapy.

Development of a Novel Anti-CD44 Variant 6 Monoclonal Antibody C44Mab-9 for Multiple Applications against Colorectal Carcinomas

CD44 is a cell surface glycoprotein, and its isoforms are produced by the alternative splicing with the standard and variant exons. The CD44 variant exon-containing isoforms (CD44v) are overexpressed in carcinomas. CD44v6 is one of the CD44v, and its overexpression predicts poor prognosis in colorectal cancer (CRC) patients. CD44v6 plays critical roles in CRC adhesion, proliferation, stemness, invasiveness, and chemoresistance. Therefore, CD44v6 is a promising target for cancer diagnosis and therapy for CRC. In this study, we established anti-CD44 monoclonal antibodies (mAbs) by immunizing mice with CD44v3-10-overexpressed Chinese hamster ovary (CHO)-K1 cells. We then characterized them using enzyme-linked immunosorbent assay, flow cytometry, western blotting, and immunohistochemistry. One of the established clones (C₄₄Mab-9; IgG₁, kappa) reacted with a peptide of the variant 6-encoded region, indicating that C₄₄Mab-9 recognizes CD44v6. Furthermore, C₄₄Mab-9 reacted with CHO/CD44v3-10 cells or CRC cell lines (COLO201 and COLO205) by flow cytometry. The apparent dissociation constant (K_D) of C₄₄Mab-9 for CHO/CD44v3-10, COLO201, and COLO205 was 8.1 × 10^-9 M, 1.7 × 10^-8 M, and 2.3 × 10^-8 M, respectively. C₄₄Mab-9 detected the CD44v3-10 in western blotting, and partially stained the formalin-fixed paraffin-embedded CRC tissues in immunohistochemistry. Collectively, C₄₄Mab-9 is useful for detecting CD44v6 in various applications.

PDPN contributes to constructing immunosuppressive microenvironment in IDH wildtype glioma

The tumor immunosuppressive microenvironment (IME) significantly affects tumor occurrence, progression, and prognosis, but the underlying molecular mechanisms remain to make known. We investigated the prognostic significance of PDPN and its role in IME in glioma. Weighted gene co-expression network analysis (WGCNA) found PDPN closely related to IDH wildtype status and higher immune score. Correlation analysis suggested PDPN was highly positively relevant to immune checkpoints expression and immune checkpoints block responding status. Correlation analysis together with verification in vitro suggested PDPN highly positively relevant tumor-associated neutrophils (TANs) and tumor-associated macrophages (TAMs). Least absolute shrinkage and selection operator (LASSO) regression employed to develop the prediction model with TANs and TAMs markers showed that high risk scores predicted worse prognosis. We highlight that PDPN overexpression is an independent prognostic indicator, and promotes macrophage M2 polarization and neutrophil degranulation, ultimately devotes to the formation of an immunosuppressive tumor microenvironment. Our findings contribute to re-recognizing the role of PDPN in IDH wildtype gliomas and implicate promising target therapy combined with immunotherapy for this highly malignant tumor.

Antitumor activities of a defucosylated anti‑EpCAM monoclonal antibody in colorectal carcinoma xenograft models

Epithelial cell adhesion molecule (EpCAM) is a type I transmembrane glycoprotein, which is highly expressed on tumor cells. As EpCAM plays a crucial role in cell adhesion, survival, proliferation, stemness, and tumorigenesis, it has been considered as a promising target for tumor diagnosis and therapy. Anti‑EpCAM monoclonal antibodies (mAbs) have been developed and have previously demonstrated promising outcomes in several clinical trials. An anti‑EpCAM mAb, EpMab‑37 (mouse IgG₁, kappa) was previously developed by the authors, using the cell‑based immunization and screening method. In the present study, a defucosylated version of anti‑EpCAM mAb (EpMab‑37‑mG2a‑f) was generated to evaluate the antitumor activity against EpCAM‑positive cells. EpMab‑37‑mG_2a‑f recognized EpCAM‑overexpressing CHO‑K1 (CHO/EpCAM) cells with a moderate binding‑affinity [dissociation constant (K_D)=2.2x10^‑8 M] using flow cytometry. EpMab‑37‑mG_2a‑f exhibited potent antibody‑dependent cellular cytotoxicity (ADCC) and complement‑dependent cytotoxicity (CDC) for CHO/EpCAM cells by murine splenocytes and complements, respectively. Furthermore, the administration of EpMab‑37‑mG_2a‑f significantly suppressed CHO/EpCAM xenograft tumor development compared with the control mouse IgG. EpMab‑37‑mG_2a‑f also exhibited a moderate binding‑affinity (K_D=1.5x10^‑8 M) and high ADCC and CDC activities for a colorectal cancer cell line (Caco‑2 cells). The administration of EpMab‑37‑mG_2a‑f to Caco‑2 tumor‑bearing mice significantly suppressed tumor development compared with the control. By contrast, EpMab‑37‑mG_2a‑f never suppressed the xenograft tumor growth of Caco‑2 cells in which EpCAM was knocked out. On the whole, these results indicate that EpMab‑37‑mG_2a‑f may exert antitumor activities against EpCAM‑positive cancers and may thus be a promising therapeutic regimen for colorectal cancer.

Pan-Cancer Analysis Identifies Tumor Cell Surface Targets for CAR-T Cell Therapies and Antibody Drug Conjugates

Tumor cells can be recognized through tumor surface antigens by immune cells and antibodies, which therefore can be used as drug targets for chimeric antigen receptor-T (CAR-T) therapies and antibody drug conjugates (ADCs). In this study, we aimed to identify novel tumor-specific antigens as targets for more effective and safer CAR-T cell therapies and ADCs. Here, we performed differential expression analysis of pan-cancer data obtained from the Cancer Genome Atlas (TCGA), and then performed a series of conditional screenings including Cox regression analysis, Pearson correlation analysis, and risk-score calculation to find tumor-specific cell membrane genes. A tumor tissue-specific and highly expressed gene set containing 3919 genes from 17 cancer types was obtained. Moreover, the prognostic roles of these genes and the functions of these highly expressed membrane proteins were assessed. Notably, 427, 584, 431 and 578 genes were identified as risk factors for LIHC, KIRC, UCEC, and KIRP, respectively. Functional enrichment analysis indicated that these tumor-specific surface proteins might confer tumor cells the ability to invade and metastasize. Furthermore, correlation analysis displayed that most overexpressed membrane proteins were positively correlated to each other. In addition, 371 target membrane protein-coding genes were sifted out by excluding proteins expressed in normal tissues. Apart from the identification of well-validated genes such as GPC3, MSLN and EGFR in the literature, we further confirmed the differential protein expression of 23 proteins: ADD2, DEF6, DOK3, ENO2, FMNL1, MICALL2, PARVG, PSTPIP1, FERMT1, PLEK2, CD109, GNG4, MAPT, OSBPL3, PLXNA1, ROBO1, SLC16A3, SLC26A6, SRGAP2, and TMEM65 in four types of tumors. In summary, our findings reveal novel tumor-specific antigens, which could be potentially used for next-generation CAR-T cell therapies and ADC discovery.

Efficacy of cancer-specific anti-podoplanin CAR-T cells and oncolytic herpes virus G47Δ combination therapy against glioblastoma

Glioblastoma is a devastating malignant brain tumor with a poor prognosis despite standard therapy. Podoplanin (PDPN), a type I transmembrane mucin-like glycoprotein that is overexpressed in various cancers, is a potential therapeutic target for the treatment of glioblastoma. We previously reported the efficacy of chimeric antigen receptor (CAR)-T cells using an anti-pan-PDPN monoclonal antibody (mAb; NZ-1)-based third-generation CAR in a xenograft mouse model. However, NZ-1 also reacted with PDPN-expressing normal cells, such as lymphatic endothelial cells, pulmonary alveolar type I cells, and podocytes. To overcome possible on-target-off-tumor effects, we produced a cancer-specific mAb (CasMab, LpMab-2)-based CAR. LpMab-2 (Lp2) reacted with PDPN-expressing cancer cells but not with normal cells. In this study, Lp2-CAR-transduced T cells (Lp2-CAR-T) specifically targeted PDPN-expressing glioma cells while sparing the PDPN-expressing normal cells. Lp2-CAR-T also killed patient-derived glioma stem cells, demonstrating its clinical potential against glioblastoma. Systemic injection of Lp2-CAR-T cells inhibited the growth of a subcutaneous glioma xenograft model in immunodeficient mice. Combination therapy with Lp2-CAR-T and oncolytic virus G47Δ, a third-generation recombinant herpes simplex virus (HSV)-1, further inhibited the tumor growth and improved survival. These findings indicate that the combination therapy of Lp2-CAR-T cells and G47Δ may be a promising approach to treat glioblastoma.

Epitope Mapping of an Anti-elephant Podoplanin Monoclonal Antibody (PMab-295) Using Enzyme-Linked Immunosorbent Assay

Podoplanin (PDPN) is a marker of lung type I alveolar cells, kidney podocytes, and lymphatic endothelial cells. The overexpression of PDPN contributes to the malignant progression of tumors. Therefore, the development of anti-PDPN monoclonal antibodies (mAbs) to animals is essential to evaluate the pathogenesis and cellular functions. Using peptide immunization, we previously developed an anti-elephant PDPN (elePDPN) mAb, PMab-295, which is useful for flow cytometry, Western blotting, and immunohistochemistry. In this study, we determined the critical epitope of PMab-295 by enzyme-linked immunosorbent assay (ELISA). We performed ELISA with the alanine-substituted peptides of elePDPN extracellular domain (amino acids 38-51), and found that PMab-295 did not recognize the alanine-substituted peptides of M41A, P44A, and E47A. Furthermore, these peptides could not inhibit the recognition of PMab-295 to elePDPN-expressing cells by flow cytometry and immunohistochemistry. The results indicate that the binding epitope of PMab-295 includes Met41, Pro44, and Glu47 of elePDPN.

Development of a Monoclonal Antibody PMab-295 Against Elephant Podoplanin

Podoplanin (PDPN) is an essential marker of lung type I alveolar cells, kidney podocytes, and lymphatic endothelial cells. Monoclonal antibodies (mAbs) that can specifically recognize PDPN in immunohistochemistry are important to analyze the development of tissues and the pathogenesis of diseases, including cancers. We have developed anti-PDPN mAbs against many animal species; however, mAbs that can recognize elephant-derived membrane proteins and distinguish the specific cell types in immunohistochemistry are limited. In this study, a novel anti-elephant PDPN (elePDPN) mAb, PMab-295 (IgG₁, kappa), was established using the peptide immunization method. PMab-295 recognized both elePDPN-overexpressed Chinese hamster ovary (CHO)-K1 cells and endogenous elePDPN-expressed LACF-NaNaI cells by flow cytometry and western blotting. Kinetic analyses using flow cytometry showed that the K_D of PMab-295 for CHO/elePDPN was 1.5 × 10^-8 M. Furthermore, PMab-295 detected elePDPN-expressing cells using immunohistochemistry. These results showed the usefulness of PMab-295 to investigate the molecular function of elePDPN and the pathogenesis of diseases.

Improved anti-solid tumor response by humanized anti-podoplanin chimeric antigen receptor transduced human cytotoxic T cells in an animal model

Recently, research has been conducted with chimeric antigen receptor (CAR)-T cells to improve efficacy against solid tumors. Humanized CAR improved the long-term survival of CAR-T cells in patients' peripheral blood, resulting in increased therapeutic efficacy. Therefore, the humanization of the CAR-gene sequence is considered an effective method. Podoplanin (PDPN) is a glycosylated transmembrane protein that is highly expressed in solid tumors and is associated with poor prognosis in patients with cancer. Therefore, PDPN is considered a biomarker and good target for cancer treatment with CAR-T cells. Previously, an anti-PDPN CAR was generated from a conventional non-humanized antibody-NZ-1, the only anti-PDPN antibody for which a CAR was produced. In this study, we investigated other anti-PDPN CARs from the antibody NZ-27, or humanized NZ-1, to enhance the therapeutic potential of CAR-T cells. The CAR signal intensity was enhanced by the efficient expression of CAR proteins on the T-cell surface of NZ-27 CAR-T cells, which show tumor-specific cytotoxicity, proinflammatory cytokine production, and anti-tumor activity against PDPN-expressing tumor xenografts in mice that were significantly better than those in non-humanized NZ-1 CAR-T cells. This article is protected by copyright. All rights reserved.

The Role of Podoplanin in the Immune System and Inflammation

Podoplanin is a small cell-surface mucin-like glycoprotein that participates in multiple physiological and pathological processes. Podoplanin exerts an important function in the immune response and is upregulated in fibroblasts, macrophages, T helper cells, and epithelial cells during inflammation. Herein, we summarize the latest knowledge on the functional expression of podoplanin in the immune system and review the contribution of podoplanin to several inflammatory diseases. Furthermore, we discuss podoplanin as a novel therapeutic target for various inflammatory diseases.

CAR T cells redirected against tumor-specific antigen glycoforms: can low-sugar antigens guarantee a sweet success?

Immune-based therapies have experienced a pronounced breakthrough in the past decades as they acquired multiple US Food and Drug Administration (FDA) approvals for various indications. To date, six chimeric antigen receptor T cell (CAR-T) therapies have been permitted for the treatment of certain patients with relapsed/refractory hematologic malignancies. However, several clinical trials of solid tumor CAR-T therapies were prematurely terminated, or they reported life-threatening treatment-related damages to healthy tissues. The simultaneous expression of target antigens by healthy organs and tumor cells is partly responsible for such toxicities. Alongside targeting tumor-specific antigens, targeting the aberrantly glycosylated glycoforms of tumor-associated antigens can also minimize the off-tumor effects of CAR-T therapies. Tn, T, and sialyl-Tn antigens have been reported to be involved in tumor progression and metastasis, and their expression results from the dysregulation of a series of glycosyltransferases and the endoplasmic reticulum protein chaperone, Cosmc. Moreover, these glycoforms have been associated with various types of cancers, including prostate, breast, colon, gastric, and lung cancers. Here, we discuss how underglycosylated antigens emerge and then detail the latest advances in the development of CAR-T-based immunotherapies that target some of such antigens.

Modulating tumor physical microenvironment for fueling CAR-T cell therapy

Chimeric antigen receptor (CAR) T cell therapy has achieved unprecedented clinical success against hematologic malignancies. However, the transition of CAR-T cell therapies for solid tumors is limited by heterogenous antigen expression, immunosuppressive microenvironment (TME), immune adaptation of tumor cells and impeded CAR-T-cell infiltration/transportation. Recent studies increasingly reveal that tumor physical microenvironment could affect various aspects of tumor biology and impose profound impacts on the antitumor efficacy of CAR-T therapy. In this review, we discuss the critical roles of four physical cues in solid tumors for regulating the immune responses of CAR-T cells, which include solid stress, interstitial fluid pressure, stiffness and microarchitecture. We highlight new strategies exploiting these features to enhance the therapeutic potency of CAR-T cells in solid tumors by correlating with the state-of-the-art technologies in this field. A perspective on the future directions for developing new CAR-T therapies for solid tumor treatment is also provided.

Heterocellular N-cadherin junctions enable nontransformed cells to inhibit the growth of adjacent transformed cells

BACKGROUND

The Src tyrosine kinase phosphorylates effector proteins to induce expression of the podoplanin (PDPN) receptor in order to promote tumor progression. However, nontransformed cells can normalize the growth and morphology of neighboring transformed cells. Transformed cells must escape this process, called "contact normalization", to become invasive and malignant. Contact normalization requires junctional communication between transformed and nontransformed cells. However, specific junctions that mediate this process have not been defined. This study aimed to identify junctional proteins required for contact normalization.

METHODS

Src transformed cells and oral squamous cell carcinoma cells were cultured with nontransformed cells. Formation of heterocellular adherens junctions between transformed and nontransformed cells was visualized by fluorescent microscopy. CRISPR technology was used to produce cadherin deficient and cadherin competent nontransformed cells to determine the requirement for adherens junctions during contact normalization. Contact normalization of transformed cells cultured with cadherin deficient or cadherin competent nontransformed cells was analyzed by growth assays, immunofluorescence, western blotting, and RNA-seq. In addition, Src transformed cells expressing PDPN under a constitutively active exogenous promoter were used to examine the ability of PDPN to override contact normalization.

RESULTS

We found that N-cadherin (N-Cdh) appeared to mediate contact normalization. Cadherin competent cells that expressed N-Cdh inhibited the growth of neighboring transformed cells in culture, while cadherin deficient cells failed to inhibit the growth of these cells. Results from RNA-seq analysis indicate that about 10% of the transcripts affected by contact normalization relied on cadherin mediated communication, and this set of genes includes PDPN. In contrast, cadherin deficient cells failed to inhibit PDPN expression or normalize the growth of adjacent transformed cells. These data indicate that nontransformed cells formed heterocellular cadherin junctions to inhibit PDPN expression in adjacent transformed cells. Moreover, we found that PDPN enabled transformed cells to override the effects of contact normalization in the face of continued N-Cdh expression. Cadherin competent cells failed to normalize the growth of transformed cells expressing PDPN under a constitutively active exogenous promoter.

CONCLUSIONS

Nontransformed cells form cadherin junctions with adjacent transformed cells to decrease PDPN expression in order to inhibit tumor cell proliferation. Cancer begins when a single cell acquires changes that enables them to form tumors. During these beginning stages of cancer development, normal cells surround and directly contact the cancer cell to prevent tumor formation and inhibit cancer progression. This process is called contact normalization. Cancer cells must break free from contact normalization to progress into a malignant cancer. Contact normalization is a widespread and powerful process; however, not much is known about the mechanisms involved in this process. This work identifies proteins required to form contacts between normal cells and cancer cells, and explores pathways by which cancer cells override contact normalization to progress into malignant cancers. Video Abstract.

Roles of Podoplanin in Malignant Progression of Tumor

Podoplanin (PDPN) is a cell-surface mucin-like glycoprotein that plays a critical role in tumor development and normal development of the lung, kidney, and lymphatic vascular systems. PDPN is overexpressed in several tumors and is involved in their malignancy. PDPN induces platelet aggregation through binding to platelet receptor C-type lectin-like receptor 2. Furthermore, PDPN modulates signal transductions that regulate cell proliferation, differentiation, migration, invasion, epithelial-to-mesenchymal transition, and stemness, all of which are crucial for the malignant progression of tumor. In the tumor microenvironment (TME), PDPN expression is upregulated in the tumor stroma, including cancer-associated fibroblasts (CAFs) and immune cells. CAFs play significant roles in the extracellular matrix remodeling and the development of immunosuppressive TME. Additionally, PDPN functions as a co-inhibitory molecule on T cells, indicating its involvement with immune evasion. In this review, we describe the mechanistic basis and diverse roles of PDPN in the malignant progression of tumors and discuss the possibility of the clinical application of PDPN-targeted cancer therapy, including cancer-specific monoclonal antibodies, and chimeric antigen receptor T technologies.

Construction of Novel Methylation-Driven Gene Model and Investigation of PARVB Function in Glioblastoma

Background

Glioblastoma multiforme (GBM) is characterized by widespread genetic and transcriptional heterogeneity. Aberrant DNA methylation plays a vital role in GBM progression by regulating gene expression. However, little is known about the role of methylation and its association with prognosis in GBM. Our aim was to explore DNA methylation-driven genes (DMDGs) and provide evidence for survival prediction and individualized treatment of GBM patients.

Methods

Use of the MethylMix R package identified DMDGs in GBM. The prognostic signature of DMDGs based on the risk score was constructed by multivariate Cox regression analysis. Receiver operating characteristics (ROC) curve and C-index were applied to assess the predictive performance of the DMDG prognostic signature. The predictive ability of the multigene signature model was validated in TCGA and CGGA cohorts. Finally, the role of DMDG β-Parvin (PARVB) was explored in vitro.

Results

The prognostic signature of DMDGs was constructed based on six genes (MDK, NMNAT3, PDPN, PARVB, SERPINB1, and UPP1). The low-risk cohort had significantly better survival than the high-risk cohort (p < 0.001). The area under the curve of the ROC of the six-gene signature was 0.832, 0.927, and 0.980 within 1, 2, and 3 years, respectively. The C-index of 0.704 indicated superior specificity and sensitivity. The six-gene model has been demonstrated to be an independent prognostic factor for GBM. In addition, joint survival analysis indicated that the MDK, NMNAT3, PARVB, SERPINB1, and UPP1 genes were significantly associated with prognosis and therapeutic targets for GBM. Importantly, our DMDG prognostic model was more suitable and accurate for low-grade gliomas. Finally, we verified that PARVB induced epithelial-mesenchymal transition partially through the JAK2/STAT3 pathway, which in turn promoted GBM cell proliferation, migration, and invasion.

Conclusion

This study demonstrated the potential value of the prognostic signature of DMDGs and provided important bioinformatic and potential therapeutic target data to facilitate individualized treatment for GBM, and to elucidate the specific mechanism by which PARVB promotes GBM progression.

Chimeric antigen receptor (CAR) immunotherapy: basic principles, current advances, and future prospects in neuro-oncology

With recent advances, chimeric antigen receptor (CAR) immunotherapy has become a promising modality for patients with refractory cancer diseases. The successful results of CAR T cell therapy in relapsed and refractory B-cell malignancies shifted the paradigm of cancer immunotherapy by awakening the scientific, clinical, and commercial interest in translating this technology for the treatment of solid cancers. This review elaborates on fundamental principles of CAR T cell therapy (development of CAR construct, challenges of CAR T cell therapy) and its application on solid tumors as well as CAR T cell therapy potential in the field of neuro-oncology. Glioblastoma (GBM) is identified as one of the most challenging solid tumors with a permissive immunological milieu and dismal prognosis. Standard multimodal treatment using maximal safe resection, radiochemotherapy, and maintenance chemotherapy extends the overall survival beyond a year. Recurrence is, however, inevitable. GBM holds several unique features including its vast intratumoral heterogeneity, immunosuppressive environment, and a partially permissive anatomic blood–brain barrier, which offers a unique opportunity to investigate new treatment approaches. Tremendous efforts have been made in recent years to investigate novel CAR targets and target combinations with standard modalities for solid tumors and GBM to improve treatment efficacy. In this review, we outline the history of CAR immunotherapy development, relevant CAR target antigens validated with CAR T cells as well as preclinical approaches in combination with adjunct approaches via checkpoint inhibition, bispecific antibodies, and second-line systemic therapies that enhance anticancer efficacy of the CAR-based cancer immunotherapy.

Immunotherapy in Glioblastoma: A Clinical Perspective

Glioblastoma is the most frequent and the most aggressive brain tumor. It is notoriously resistant to current treatments, and the prognosis remains dismal. Immunotherapies have revolutionized the treatment of numerous cancer types and generate great hope for glioblastoma, alas without success until now. In this review, the rationale underlying immune targeting of glioblastoma, as well as the challenges faced when targeting these highly immunosuppressive tumors, are discussed. Innovative immune-targeting strategies including cancer vaccines, oncolytic viruses, checkpoint blockade inhibitors, adoptive cell transfer, and CAR T cells that have been investigated in glioblastoma are reviewed. From a clinical perspective, key clinical trial findings and ongoing trials are discussed for each approach. Finally, limitations, either biological or arising from trial designs are analyzed, and strategies to overcome them are presented. Proof of efficacy for immunotherapy approaches remains to be demonstrated in glioblastoma, but our rapidly expanding understanding of its biology, its immune microenvironment, and the emergence of novel promising combinatorial approaches might allow researchers to finally fulfill the medical need for GBM patients.

Epitope Mapping of the Anti-California Sea Lion Podoplanin Monoclonal Antibody PMab-269 Using Alanine-Scanning Mutagenesis and ELISA

Podoplanin (PDPN) plays a pivotal role in platelet aggregation, embryo development, and tumor progression. PDPN is universally expressed in many mammalian species, and is considered a typical lymphatic endothelial cell marker. We have previously developed the mouse anti-California sea lion (Zalophus californianus) PDPN (seaPDPN) monoclonal antibody (mAb), clone PMab-269, which is suitable for different experimental applications, including flow cytometry, Western blotting, and immunohistochemistry. In this study, we identified the PMab-269 epitope of the seaPDPN by enzyme-linked immunosorbent assay using deletion mutants and point mutants generated for seaPDPN. Our results demonstrated that PMab-269 recognized the peptide, corresponding to the amino acids 63-82 of seaPDPN. Furthermore, the reactions of PMab-269 to seven alanine-substituted peptides, such as P68A, D76A, F77A, H78A, L79A, E80A, and D81A, were abolished among 20 alanine-substituted peptides. We identified the seven amino acids (Pro68, Asp76, Phe77, His78, Leu79, Glu80, and Asp81) as the critical epitope targeted by PMab-269. The successful identification of the PMab-269 epitope might contribute to the pathophysiological investigations of seaPDPN.

Advances in Immunotherapy for Adult Glioblastoma

Simple Summary

Therapy failure and disease recurrence are hallmarks of glioblastoma (GBM), the most common and lethal tumor in adults that originates in the brain. Despite aggressive standards of care, tumor recurrence is inevitable with no standardized second-line therapy. Recent clinical studies evaluating therapies that augment the anti-tumor immune response (i.e., immunotherapies) have yielded promising results in subsets of GBM patients. Here, we summarize clinical studies in the past decade that evaluate vaccines, immune checkpoint inhibitors and chimeric antigen receptor (CAR) T cells for treatment of GBM. Although immunotherapies have yet to return widespread efficacy for the majority of GBM patients, critical insights from completed and ongoing clinical trials are informing development of the next generation of therapies, with the goal to alleviate disease burden and extend patient survival.

Abstract

Despite aggressive multimodal therapy, glioblastoma (GBM) remains the most common malignant primary brain tumor in adults. With the advent of therapies that revitalize the anti-tumor immune response, several immunotherapeutic modalities have been developed for treatment of GBM. In this review, we summarize recent clinical and preclinical efforts to evaluate vaccination strategies, immune checkpoint inhibitors (ICIs) and chimeric antigen receptor (CAR) T cells. Although these modalities have shown long-term tumor regression in subsets of treated patients, the underlying biology that may predict efficacy and inform therapy development is being actively investigated. Common to all therapeutic modalities are fundamental mechanisms of therapy evasion by tumor cells, including immense intratumoral heterogeneity, suppression of the tumor immune microenvironment and low mutational burden. These insights have led efforts to design rational combinatorial therapies that can reignite the anti-tumor immune response, effectively and specifically target tumor cells and reliably decrease tumor burden for GBM patients.

Novel antigens of CAR T cell therapy: New roads; old destination

Chimeric antigen receptor T cell (CAR-T) therapy has so far proved itself as a reliable therapeutic option for the treatment of relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL), diffuse large B-cell lymphoma (DLBCL), multiple myeloma (MM), and mantle cell lymphoma (MCL). However, this picture is not as colorful when it comes to the treatment of solid tumors mainly due to the lack of definitive tumor antigens, as well as the immunosuppressive tumor microenvironments and poor CAR-T infiltration. The recent developments in bioinformatics and cell biology, such as single-cell RNA sequencing, have offered silver linings in the subject of tumor antigen discovery. In the current review, we summarize the development of some CAR-T therapies that target novel tumor antigens, rather than the traditionally CAR-T-targeted ones, and briefly discuss the clinical antitumor achievements of those evaluated in patients, so far. Furthermore, we propose some tumor antigens that might someday be therapeutically beneficial while targeted by CAR-Ts based on the experimental evaluations of their specific monoclonal antibodies.

Development of Monoclonal Antibody PMab-269 Against California Sea Lion Podoplanin

The development of protein-specific antibodies is essential for understanding a wide variety of biological phenomena. Parasitic and viral infections and cancers are known to occur within California sea lion (Zalophus californianus) populations. However, sensitive and specific monoclonal antibodies (mAbs) for the pathophysiological analysis of California sea lion tissues have not yet been developed. A type I transmembrane glycoprotein, podoplanin (PDPN), is a known diagnostic marker of lymphatic endothelial cells. We have previously developed several anti-PDPN mAbs in various mammalian species, with applications in flow cytometry, Western blotting, and immunohistochemistry. In this study, we established a novel mAb against California sea lion PDPN (seaPDPN), clone PMab-269 (mouse IgG₁, kappa), using a Cell-Based Immunization and Screening method. PMab-269 is specifically detected in seaPDPN-overexpressed Chinese hamster ovary (CHO)-K1 cells using flow cytometry and Western blotting. Moreover, PMab-269 clearly identified pulmonary type I alveolar cells, renal podocytes, and colon lymphatic endothelial cells in California sea lion tissues using immunohistochemistry. These findings demonstrate the usefulness of PMab-269 for the pathophysiological analysis of lung, kidney, and lymphatic tissues of the California sea lion.

Quantifying the limits of CAR T-cell delivery in mice and men

CAR (Chimeric Antigen Receptor) T cells have demonstrated clinical success for the treatment of multiple lymphomas and leukaemias, but not for various solid tumours, despite promising data from murine models. Lower effective CAR T-cell delivery rates to human solid tumours compared to haematological malignancies in humans and solid tumours in mice might partially explain these divergent outcomes. We used anatomical and physiological data for human and rodent circulatory systems to calculate the typical perfusion of healthy and tumour tissues, and estimated the upper limits of immune cell delivery rates across different organs, tumour types and species. Estimated maximum delivery rates were up to 10 000-fold greater in mice than humans yet reported CAR T-cell doses are typically only 10-100-fold lower in mice, suggesting that the effective delivery rates of CAR T cells into tumours in clinical trials are far lower than in corresponding mouse models. Estimated delivery rates were found to be consistent with published positron emission tomography data. Results suggest that higher effective human doses may be needed to drive efficacy comparable to mouse solid tumour models, and that lower doses should be tested in mice. We posit that quantitation of species and organ-specific delivery and homing of engineered T cells will be key to unlocking their potential for solid tumours.

New Era of Immunotherapy in Pediatric Brain Tumors: Chimeric Antigen Receptor T-Cell Therapy

Immunotherapy, including chimeric antigen receptor (CAR) T-cell therapy, immune checkpoint inhibitors, cancer vaccines, and dendritic cell therapy, has been incorporated as a fifth modality of modern cancer care, along with surgery, radiation, chemotherapy, and target therapy. Among them, CAR T-cell therapy emerges as one of the most promising treatments. In 2017, the first two CAR T-cell drugs, tisagenlecleucel and axicabtagene ciloleucel for B-cell acute lymphoblastic leukemia (ALL) and diffuse large B-cell lymphoma (DLBCL), respectively, were approved by the Food and Drug Administration (FDA). In addition to the successful applications to hematological malignancies, CAR T-cell therapy has been investigated to potentially treat solid tumors, including pediatric brain tumor, which serves as the leading cause of cancer-associated death for children and adolescents. However, the employment of CAR T-cell therapy in pediatric brain tumors still faces multiple challenges, such as CAR T-cell transportation and expansion through the blood–brain barrier, and identification of the specific target antigen on the tumor surface and immunosuppressive tumor microenvironment. Nevertheless, encouraging outcomes in both clinical and preclinical trials are coming to light. In this article, we outline the current propitious progress and discuss the obstacles needed to be overcome in order to unveil a new era of treatment in pediatric brain tumors.

Phase I/II Clinical Trial of the Anti-Podoplanin Monoclonal Antibody Therapy in Dogs with Malignant Melanoma

Podoplanin (PDPN), a small transmembrane mucin-like glycoprotein, is ectopically expressed on tumor cells. PDPN is known to be linked with several aspects of tumor malignancies in certain types of human and canine tumors. Therefore, it is considered to be a novel therapeutic target. Monoclonal antibodies targeting PDPN expressed in human tumor cells showed obvious anti-tumor effects in preclinical studies using mouse models. Previously, we generated a cancer-specific mouse-dog chimeric anti-PDPN antibody, P38Bf, which specifically recognizes PDPN expressed in canine tumor cells. In this study, we investigated the safety and anti-tumor effects of P38Bf in preclinical and clinical trials. P38Bf showed dose-dependent antibody-dependent cellular cytotoxicity against canine malignant melanoma cells. In a preclinical trial with one healthy dog, P38Bf administration did not induce adverse effects over approximately 2 months. In phase I/II clinical trials of three dogs with malignant melanoma, one dog vomited, and all dogs had increased serum levels of C-reactive protein, although all adverse effects were grade 1 or 2. Severe adverse effects leading to withdrawal of the clinical trial were not observed. Furthermore, one dog had stable disease with P38Bf injections. This is the first reported clinical trial of anti-PDPN antibody therapy using spontaneously occurring canine tumor models.

Tumor-infiltrating podoplanin+ cells in gastric cancer: clinical outcomes and association with immune contexture

Podoplanin (PDPN) has been proved to have significant immunoregulatory effects in several types of malignancies and is considered to be a novel immune checkpoint molecule. However, the clinical significance of PDPN and its potential influence on immune contexture in gastric cancer remain obscure. Here, we aimed to investigate the clinical outcomes and immunoregulatory role of tumor-infiltrating PDPN⁺ cells (tPDPNs) in gastric cancer. A total of 454 tumor tissue microarray specimens and 68 fresh tumor tissues of gastric cancer patients from Zhongshan Hospital, and transcriptional data of 293 gastric cancer patients from The Cancer Genome Atlas were included. We demonstrated that tPDPNs high subgroup experienced worse overall survival and disease-free survival, and indicated inferior therapeutic responsiveness to fluorouracil-based adjuvant chemotherapy (ACT) in gastric cancer. The abundance of tPDPNs was correlated with an immunoevasive contexture characterized by pro-tumor macrophage and dysfunctional CD8⁺ T cell infiltration. Moreover, dysfunctional CD8⁺ T cells in tPDPNs high subgroup exhibited decreased interferon-γ, granzyme B and perforin-1 expression yet elevated programmed cell death-1 (PD-1) and T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) expression. Stratification of gastric cancer patients into different risk groups based on tPDPNs and CD8⁺ T cells showed distinct prognosis, responsiveness to ACT and molecular characteristics. This study revealed that the abundance of tPDPNs could identify an immunoevasive contexture and might be applied as an independent predictor for poor prognosis and suboptimal ACT responsiveness. Thus, we recommended tPDPNs as a promising therapeutic target in gastric cancer.

Prognosis Analysis and Validation of m6A Signature and Tumor Immune Microenvironment in Glioma

Glioma is one of the most typical intracranial tumors, comprising about 80% of all brain malignancies. Several key molecular signatures have emerged as prognostic biomarkers, which indicate room for improvement in the current approach to glioma classification. In order to construct a more veracious prediction model and identify the potential prognosis-biomarker, we explore the differential expressed m⁶A RNA methylation regulators in 665 gliomas from TCGA-GBM and TCGA-LGG. Consensus clustering was applied to the m6A RNA methylation regulators, and two glioma subgroups were identified with a poorer prognosis and a higher grade of WHO classification in cluster 1. The further chi-squared test indicated that the immune infiltration was significantly enriched in cluster 1, indicating a close relation between m⁶A regulators and immune infiltration. In order to explore the potential biomarkers, the weighted gene co-expression network analysis (WGCNA), along with Least absolute shrinkage and selection operator (LASSO), between high/low immune infiltration and m⁶A cluster 1/2 groups were utilized for the hub genes, and four genes (TAGLN2, PDPN, TIMP1, EMP3) were identified as prognostic biomarkers. Besides, a prognostic model was constructed based on the four genes with a good prediction and applicability for the overall survival (OS) of glioma patients (the area under the curve of ROC achieved 0.80 (0.76-0.83) and 0.72 (0.68-0.76) in TCGA and Chinese Glioma Genome Atlas (CGGA), respectively). Moreover, we also found PDPN and TIMP1 were highly expressed in high-grade glioma from The Human Protein Atlas database and both of them were correlated with m6A and immune cell marker in glioma tissue samples. In conclusion, we construct a novel prognostic model which provides new insights into glioma prognosis. The PDPN and TIMP1 may serve as potential biomarkers for prognosis of glioma.

Podoplanin as an Attractive Target of CAR T Cell Therapy

To date, various kinds of cancer immunotherapy methods have been developed, but T cell immunotherapy is one of the most promising strategies. In general, T cell receptor (TCR) or chimeric antigen receptor (CAR) is used to modify the antigen specificity of T cells. CARs possess an underlying potential with treatment efficacy to treat a broad range of cancer patients compared with TCRs. Although a variety of CAR molecules have been developed so far, the clinical application for solid tumors is limited partly due to its adverse effect known as “on-target off-tumor toxicity”. Therefore, it is very important for CAR T cell therapy to target specific antigens exclusively expressed by malignant cells. Here, we review the application of T cell immunotherapy using specific antigen receptor molecules and discuss the possibility of the clinical application of podoplanin-targeted CAR derived from a cancer-specific monoclonal antibody (CasMab).

CAR T Cell Therapy for Pediatric Brain Tumors

Chimeric Antigen Receptor (CAR) T cell therapy has recently begun to be used for solid tumors such as glioblastoma multiforme. Many children with pediatric malignant brain tumors develop extensive long-term morbidity of intensive multimodal curative treatment. Others with certain diagnoses and relapsed disease continue to have limited therapies and a dismal prognosis. Novel treatments such as CAR T cells could potentially improve outcomes and ameliorate the toxicity of current treatment. In this review, we discuss the potential of using CAR therapy for pediatric brain tumors. The emerging insights on the molecular subtypes and tumor microenvironment of these tumors provide avenues to devise strategies for CAR T cell therapy. Unique characteristics of these brain tumors, such as location and associated morbid treatment induced neuro-inflammation, are novel challenges not commonly encountered in adult brain tumors. Despite these considerations, CAR T cell therapy has the potential to be integrated into treatment schema for aggressive pediatric malignant brain tumors in the future.

Podoplanin expression is a prognostic biomarker but may be dispensable for the malignancy of glioblastoma

BACKGROUND

Treatment options of glioblastoma, the most aggressive primary brain tumor with frequent relapses and high mortality, are still very limited, urgently calling for novel therapeutic targets. Expression of the glycoprotein podoplanin correlates with poor prognosis in various cancer entities, including glioblastoma. Furthermore, podoplanin has been associated with tumor cell migration and proliferation in vitro; however, experimental data on its function in gliomagenesis in vivo are still missing. Hence, we have functionally investigated the impact of podoplanin on glioblastoma in a preclinical mouse model to evaluate its potential as a therapeutic target.

METHODS

Fluorescence activated cell sorting, genome-wide expression analysis, and clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-mediated deletion of podoplanin in patient-derived human glioblastoma cells were combined with organotypic brain slice cultures and intracranial injections into mice.

RESULTS

We defined a malignant gene signature in tumor cells with high podoplanin expression. The increase and/or maintenance of high podoplanin expression in serial transplantations and in podoplaninlow-sorted glioblastoma cells during outgrowth indicated the association of high podoplanin expression and poor outcome. Unexpectedly, similar rates of proliferation, apoptosis, angiogenesis, and invasion were observed in control and podoplanin-deleted tumors. Accordingly, neither tumor growth nor survival was affected upon podoplanin loss.

CONCLUSION

We report that tumor progression occurs independently of podoplanin. Thus, in contrast to previous suggestions, blocking of podoplanin does not represent a promising therapeutic approach. However, as podoplanin is associated with tumor aggressiveness and progression, we propose the cell surface protein as a biomarker for poor prognosis.

Effect of CRISPR/Cas9-Mediated PD-1-Disrupted Primary Human Third-Generation CAR-T Cells Targeting EGFRvIII on In Vitro Human Glioblastoma Cell Growth

Glioblastoma (GBM), which is the most common malignant brain tumor, is resistant to standard treatments. Immunotherapy might be a promising alternative for the treatment of this cancer. Chimeric antigen receptor (CAR) is an artificially modified fusion protein that can be engineered to direct the specificity and function of T cells against tumor antigens. However, the antitumor effects of EGFRvIII-targeting CAR-T (EvCAR-T) cells in GBM are limited. The inhibitory effect is induced by the interaction between programmed cell death protein 1 (PD-1) on activated EvCAR-T cells and its ligands on GBM cells. In the present study, PD-1-disrupted EvCAR-T cells were established using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9). The sgRNA/Cas9 expression vectors designed precisely disrupted the target region of PD-1 and inhibited the expression of PD-1 in EvCAR-T cells. The PD-1-disrupted EvCAR-T cells had an in vitro growth inhibitory effect on EGFRvIII-expressing GBM cells without altering the T-cell phenotype and the expression of other checkpoint receptors. In the future, the in vivo antitumor effect of this vector should be evaluated in order to determine if it could be applied clinically for improving the efficacy of EvCAR-T cell-based adoptive immunotherapy for GBM.

GPC1 specific CAR-T cells eradicate established solid tumor without adverse effects and synergize with anti-PD-1 Ab

Current xenogeneic mouse models cannot evaluate on-target off-tumor adverse effect, hindering the development of chimeric antigen receptor (CAR) T cell therapies for solid tumors, due to limited human/mouse cross-reactivity of antibodies used in CAR and sever graft-versus-host disease induced by administered human T cells. We have evaluated safety and antitumor efficacy of CAR-T cells targeting glypican-1 (GPC1) overexpressed in various solid tumors. GPC1-specific human and murine CAR-T cells generated from our original anti-human/mouse GPC1 antibody showed strong antitumor effects in xenogeneic and syngeneic mouse models, respectively. Importantly, the murine CAR-T cells enhanced endogenous T cell responses against a non-GPC1 tumor antigen through the mechanism of antigen-spreading and showed synergistic antitumor effects with anti-PD-1 antibody without any adverse effects in syngeneic models. Our study shows the potential of GPC1 as a CAR-T cell target for solid tumors and the importance of syngeneic and xenogeneic models for evaluating their safety and efficacy.

Wild-Type IDH1 and Mutant IDH1 Opposingly Regulate Podoplanin Expression in Glioma

Isocitrate dehydrogenase (IDH) mutations occur frequently in lower-grade gliomas, which result in genome-wide epigenetic alterations. The wild-type IDH1 is reported to participate in lipid biosynthesis and amino acid metabolism, but its role in tumorigenesis is still unclear. In this study, the expressions of IDH1 and podoplanin (Pdpn) were determined in IDH-mutated and IDH-wild-type gliomas, and their relationships in glioma were further analyzed. In addition, the regulation of wild-type IDH1 and mutant IDH1 on Pdpn expression was investigated by luciferase assays and promoter methylation analysis. Our study showed that Pdpn was almost undetectable in IDH-mutated glioma but strongly expressed in higher-grade IDH-wild-type glioma. Pdpn overexpression promoted the migration of glioma cells but had little effect on cell growth. Moreover, Pdpn expression was positively correlated with the increased wild-type IDH1 levels in IDH-wild-type glioma. Consistently, the wild-type IDH1 greatly promoted the transcription and expression of Pdpn, but the mutant IDH1 and D-2-hydroxyglutarate significantly suppressed Pdpn expression in glioma cells. Besides, our results revealed that the methylation of CpG islands in the Pdpn promoter was opposingly regulated by wild-type and mutant IDH1 in glioma. Collectively, our results indicated that wild-type and mutant IDH1 opposingly controlled the Pdpn expression in glioma by regulating its promoter methylation, which provides a basis for understanding the relationship between wild-type and mutant IDH1 in epigenetic regulation and tumorigenesis.

Adoptive Cell Therapy: A Novel and Potential Immunotherapy for Glioblastoma

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults with very poor prognosis and few advances in its treatment. Recently, fast-growing cancer immunotherapy provides a glimmer of hope for GBM treatment. Adoptive cell therapy (ACT) aims at infusing immune cells with direct anti-tumor activity, including tumor-infiltrating lymphocyte (TIL) transfer and genetically engineered T cells transfer. For example, complete regressions in patients with melanoma and refractory lymphoma have been shown by using naturally tumor-reactive T cells and genetically engineered T cells expressing the chimeric anti-CD19 receptor, respectively. Recently, the administration of ACT showed therapeutic potentials for GBM treatment as well. In this review, we summarize the success of ACT in the treatment of cancer and provide approaches to overcome some challenges of ACT to allow its adoption for GBM treatment.

Chimeric antigen receptor T-cell immunotherapy for glioblastoma: practical insights for neurosurgeons

The prognosis for glioblastoma (GBM) remains exceedingly poor despite state-of-the-art multimodal therapy. Immunotherapy, particularly with cytotoxic T cells, represents a promising alternative. Perhaps the most prominent T-cell technology is the chimeric antigen receptor (CAR), which in 2017 received accelerated approval from the Food and Drug Administration for the treatment of hematological malignancies. Several CARs for GBM have been recently tested in clinical trials with exciting results. The authors review these clinical data and discuss areas of ongoing research.