Neuroblastoma, a malignancy of multipotent embryonic neural crest cells, is the most common extracranial solid cancer in childhood and most common cancer in infancy. Cellular phenotype has been shown to be an important determinant of the malignant potential in human neuroblastoma cells and tumors. Whereas neuroblastic (N-type) are moderately malignant and nonneuronal (S-type) cells are nonmalignant, I-type stem cells are highly tumorigenic, irrespective of N-myc amplification status. In the present study, we sought to determine which genes were overexpressed in the I-type cells which might characterize and maintain the stem cell state and/or malignancy of human neuroblastoma cancer stem cells. We used a microarray platform to compare the steady-state expression levels of mRNAs from 13 human neuroblastoma cell lines representing the three cellular phenotypes. Using qRT-PCR and Western blot analyses, we identified seven genes whose expression is consistently elevated exclusively in neuroblastoma cancer stem cells: CD133, KIT, NOTCH1, GPRC5C, PIGF2, TRKB, and LNGFR. Moreover, we show that the genes are phenotype specific, as differentiation of I-type BE(2)-C cells to either an N- or S-type morphology results in significantly reduced mRNA expression. Finally, we show that NOTCH1 plays an important role in maintaining the stem cell phenotype. The identification and characterization of these genes, elevated in highly malignant neuroblastoma stem cells, could provide the basis for developing novel therapies for treatment of this lethal childhood cancer.
Abstract Background: EGFR and HER2 are highly expressed in many pancreatic cancers which strongly correlate with poorer prognoses. We tested homodimeric (EGFRxEGFR or HER2xHER2) and heterodimeric (EGFRxHER2) T cell-engaging bispecific antibodies (BsAbs) to direct polyclonal T cells to these antigens on pancreatic tumors. Methods: We used the 2+2 IgG(L)-scFv format to create BsAbs, previously shown to have exceptional anti-tumor properties compared to other structural platforms. These BsAbs utilize two anti-CD3 scFvs attached to the light chains of an IgG to engage T cells while retaining bivalent binding to tumor antigens with both Fab arms. Anti-EGFR was based on the Cetuximab and anti-HER2 on the Trastuzumab amino acid sequences. Using a ‘knob-into-hole’ strategy, we generated an EGFRxHER2 heterodimeric BsAb bearing one Fab specific for EGFR and one for HER2. T cells were tagged with luciferase for tracking by bioluminescence for in vivo trafficking studies. Results: The EGFRxEGFR, HER2xHER2, and EGFRxHER2 BsAbs demonstrate high avidity (KD: 2pM to 300 pM) and T cell-mediated cytotoxicity against several human pancreatic ductal adenocarcinoma (PDAC) cell lines in vitro with EC50s in the picomolar range (0.17pM to 18pM). They mediate potent T cell-mediated antitumor effects against subcutaneous PDAC xenografts and were highly efficient in driving human polyclonal T cells into tumors as measured by bioluminescence. To examine the importance of anti-tumor valency in antitumor effects, EGFR and HER2 BsAbs were heterodimerized with a CD33 control BsAb to generate EGFRxCD33 and HER2xCD33 BsAbs. Both EGFRxCD33 and HER2xCD33 BsAbs showed modest reductions in target avidity by surface plasmon resonance (2.7-fold and 12.6-fold, respectively), cell binding strength by FACS (8.0-fold and 63.6-fold) and cytotoxicity (7.7-fold and 47.2-fold) compared to their homodimeric counterparts and, remarkably, showed no therapeutic efficacy against SW1990 cell line-derived and patient-derived PDAC xenografts, correlating with reduced tumor-infiltrating bioluminescent T cells, when compared to EGFRxHER2 BsAb. When tested against SW1990 with CRISPR-mediated target KOs, only HER2xHER2 BsAb treatment could eliminate EGFR-KO tumors, while EGFRxEGFR and EGFRxHER2 BsAbs were ineffective. Conversely, in HER2-KO SW1990 tumors, while EGFRxEGFR BsAb demonstrated strong tumor control, HER2xHER2 and EGFRxHER2 BsAbs demonstrated only weak activity. Conclusion: EGFR and HER2 were useful targets for driving T cell infiltration and tumor ablation. HER2 was overall more effective as a target when compared to EGFR for pancreatic cancer in vivo. Bivalent Fab binding to tumor was critical for robust anti-tumor effect in vivo even when in vitro differences of monovalent BsAb were less obvious. EGFRxHER2 heterodimeric BsAb exhibited potent antitumor efficacy against EGFR(+)HER2(+) double positive PDAC xenografts, but not single-positive tumors, and could offer a strategy to spare healthy single-positive tissues to reduce ‘on target/off tumor’ side effects. Citation Format: Alan W. Long, Brian Santich, Hongfen Guo, Nai-Kong Cheung. Heterodimeric bispecific antibodies for highly specific treatment of EGFR(+)HER2(+) pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C022.
Tumor-restricted surface antigens may be targets for diagnosis and immune-based therapies. Monoclonal antibody 8H9 is a murine IgG1 hybridoma derived from the fusion of mouse myeloma SP2/0 cells and splenic lymphocytes from BALB/c mice immunized with human neuroblastoma. By immunohistochemistry, 8H9 was highly reactive with human brain tumors, childhood sarcomas, and neuroblastomas, and less so with adenocarcinomas. Among primary brain tumors, 15 of 17 glioblastomas, 3 of 4 mixed gliomas, 4 of 11 oligodendrogliomas, 6 of 8 astrocytomas, 2 of 2 meningiomas, 3 of 3 schwannomas, 2 of 2 medulloblastomas, 1 of 1 neurofibroma, 1 of 2 neuronoglial tumors, 2 of 3 ependymomas, and 1 of 1 pineoblastoma tested positive. Among sarcomas, 21 of 21 Ewing's/primitive neuroectodermal tumor, 28 of 29 rhabdomyosarcomas, 28 of 29 osteosarcomas, 35 of 37 desmoplastic small round cell tumors, 2 of 3 synovial sarcomas, 4 of 4 leiomyosarcomas, 1 of 1 malignant fibrous histiocytoma, and 2 of 2 undifferentiated sarcomas tested positive with 8H9. Eighty-seven of 90 neuroblastomas, 12 of 16 melanomas, 3 of 4 hepatoblastomas, 7 of 8 Wilms' tumors, 3 of 3 rhabdoid tumors, and 12 of 27 adenocarcinomas also tested positive. In contrast, 8H9 was nonreactive with normal human tissues including bone marrow, colon, stomach, heart, lung, muscle, thyroid, testes, pancreas, and human brain (frontal lobe, cerebellum, pons, and spinal cord). Reactivity with normal cynomolgus monkey tissue was restricted similarly. Indirect immunofluorescence localized the antigen recognized by 8H9 to the cell membrane. The antigen is proteinase sensitive and is not easily modulated off the cell surface. 8H9 immunoprecipitated a M(r) 58,000 band after N-glycanase treatment, most likely a protein with a heterogeneous degree of glycosylation. This novel antibody-antigen system may have potential for tumor targeting.
Clearing agents (CAs) can rapidly remove nonlocalized targeting biomolecules from circulation for hepatic catabolism, thereby enhancing the therapeutic index (TI), especially for blood (marrow), of the subsequently administered radioisotope in any multistep pretargeting strategy. Herein we describe the synthesis and in vivo evaluation of a fully synthetic glycodendrimer-based CA for DOTA-based pretargeted radioimmunotherapy (DOTA-PRIT). The novel dendron–CA consists of a nonradioactive yttrium-DOTA-Bn molecule attached via a linker to a glycodendron displaying 16 terminal α-thio-N-acetylgalactosamine (α-SGalNAc) units (CCA α-16-DOTA-Y3+; molecular weight: 9059 Da). Pretargeting [177Lu]LuDOTA-Bn with CCA α-16-DOTA-Y3+ to GPA33-expressing SW1222 human colorectal xenografts was highly effective, leading to absorbed doses of [177Lu]LuDOTA-Bn for blood, tumor, liver, spleen, and kidneys of 11.7, 468, 9.97, 5.49, and 13.3 cGy/MBq, respectively. Tumor-to-normal tissues absorbed-dose ratios (i.e., TIs) ranged from 40 (e.g., for blood and kidney) to about 550 for stomach.
In the last grant period we have focused on multi-step targeting methodologies (MST), as a method for delivery of high dose to the tumor, with low dose to the bone marrow. We have explored uptake in colorectal, pancreatic and prostate cancer, using an special preparation, developed in collaboration with NeoRex A high tumor/bone marrow ratio is clearly achieved with MST, but with a cost, namely the higher dose to normal kidney. For this reason, we have in particular, (a) looked dosimetry for both tumor and normal organ, and especially renal dosimetry, which appears to be the target organ, for Y-90. (b) In parallel with this we have explored the dosimetry of very high dose rate radionuclides, including Holmium-166. (c) In addition, with NaiKong Cheung, we have developed a new MST construct based on the anti-GD2 targeting 5F11; (d) we have successfully completed development of s-factor tables for mice. In summary, renal dosimetry is dominated by about 4-5% of the injected dose being held long-term in the renal cortex, probably in the proximal tubule, due to the universal uptake of small proteins. This appears to be a function of a biotynlated protein binding of the strept-avidin construct, to HSP70. This cortical uptake has caused us to reconsider renal dosimetry as a whole, with the smaller mass of the cortex, rather than the whole kidney, as the target organ. These insights into dosimetry will be of great importance as MST, becomes more common in clinical practice.
Success of T cell immunotherapy hinges on the tumor microenvironment (TME), and abnormal tumor vasculature is a hallmark of most solid tumors and associated with immune evasion. The efficacy of T cell engaging bispecific antibody (BsAb) treatment relies on the successful trafficking and cytolytic activity of T cells in solid tumors. Normalization of tumor vasculature using vascular endothelial growth factor (VEGF) blockades could improve efficacy of BsAb-based T cell immunotherapy.Anti-human VEGF (bevacizumab, BVZ) or anti-mouse VEGFR2 antibody (DC101) was used as VEGF blockade, and ex vivo armed T cells (EATs) carrying anti-GD2, anti-HER2, or anti-glypican3 (GPC3) IgG-(L)-scFv platformed BsAb were used. BsAb-driven intratumoral T cell infiltration and in vivo antitumor response were evaluated using cancer cell line-derived xenografts (CDXs) or patient-derived xenografts (PDXs) carried out in BALB-Rag2-/-IL-2R-γc-KO (BRG) mice. VEGF expression on human cancer cell lines was analyzed by flow cytometry, and VEGF levels in mouse serum were measured using VEGF Quantikine ELISA Kit. Tumor infiltrating lymphocytes (TILs) were evaluated using flow cytometry and by bioluminescence; both TILs and tumor vasculature were studied using immunohistochemistry.VEGF expression on cancer cell lines increased with seeding density in vitro. BVZ significantly reduced serum VEGF levels in mice. BVZ or DC101 increased high endothelial venules (HEVs) in the TME and substantially enhanced (2.1-8.1 fold) BsAb-driven T cell infiltration into neuroblastoma and osteosarcoma xenografts, which was preferential for CD8(+) TILs versus CD4(+) TILs, leading to superior antitumor effects in multiple CDX and PDX tumor models without added toxicities.VEGF blockade using specific antibodies against VEGF or VEGFR2 increased HEVs in the TME and cytotoxic CD8(+) TILs, significantly improving the therapeutic efficacy of EAT strategies in preclinical models, supporting the clinical investigation of VEGF blockades to further enhance BsAb-based T cell immunotherapies.
The norepinephrine transporter (NET) is a critical regulator of catecholamine uptake in normal physiology and is expressed in neuroendocrine tumors like neuroblastoma. Although the norepinephrine analog, meta-iodobenzylguanidine (MIBG), is an established substrate for NET, (123)I/(131)I-MIBG has several clinical limitations for diagnostic imaging. In the current studies, we evaluated meta-[(18)F]-fluorobenzylguanidine ([(18)F]-MFBG) and compared it with (123)I-MIBG for imaging NET-expressing neuroblastomas.NET expression levels in neuroblastoma cell lines were determined by Western blot and (123)I-MIBG uptake assays. Five neuroblastoma cell lines and two xenografts (SK-N-BE(2)C and LAN1) expressing different levels of NET were used for comparative in vitro and in vivo uptake studies.The uptake of [(18)F]-MFBG in cells was specific and proportional to the expression level of NET. Although [(18)F]-MFBG had a 3-fold lower affinity for NET and an approximately 2-fold lower cell uptake in vitro compared with that of (123)I-MIBG, the in vivo imaging and tissue radioactivity concentration measurements demonstrated higher [(18)F]-MFBG xenograft uptake and tumor-to-normal organ ratios at 1 and 4 hours after injection. A comparison of 4 hours [(18)F]-MFBG PET (positron emission tomography) imaging with 24 hours (123)I-MIBG SPECT (single-photon emission computed tomography) imaging showed an approximately 3-fold higher tumor uptake of [(18)F]-MFBG, but slightly lower tumor-to-background ratios in mice.[(18)F]-MFBG is a promising radiopharmaceutical for specifically imaging NET-expressing neuroblastomas, with fast pharmacokinetics and whole-body clearance. [(18)F]-MFBG PET imaging shows higher sensitivity, better detection of small lesions with low NET expression, allows same day scintigraphy with a shorter image acquisition time, and has the potential for lower patient radiation exposure compared with (131)I/(123)I-MIBG.
