AXL Inhibition Improves the Antitumor Activity of Chimeric Antigen Receptor T Cells.

The receptor tyrosine kinase AXL is a member of the TYRO3, AXL, and proto-oncogene tyrosine-protein kinase MER family and plays pleiotropic roles in cancer progression. AXL is expressed in immunosuppressive cells, which contributes to decreased efficacy of immunotherapy. Therefore, we hypothesized that AXL inhibition could serve as a strategy to overcome resistance to chimeric antigen receptor T (CAR T)-cell therapy. To test this, we determined the impact of AXL inhibition on CD19-targeted CAR T (CART19)-cell functions. Our results demonstrate that T cells and CAR T cells express high levels of AXL. Specifically, higher levels of AXL on activated Th2 CAR T cells and M2-polarized macrophages were observed. AXL inhibition with small molecules or via genetic disruption in T cells demonstrated selective inhibition of Th2 CAR T cells, reduction of Th2 cytokines, reversal of CAR T-cell inhibition, and promotion of CAR T-cell effector functions. AXL inhibition is a novel strategy to enhance CAR T-cell functions through two independent, but complementary, mechanisms: targeting Th2 cells and reversing myeloid-induced CAR T-cell inhibition through selective targeting of M2-polarized macrophages.

GM-CSF inhibition reduces cytokine release syndrome and neuroinflammation but enhances CAR-T cell function in xenografts.

Chimeric antigen receptor T (CAR-T) cell therapy is a new pillar in cancer therapeutics; however, its application is limited by the associated toxicities. These include cytokine release syndrome (CRS) and neurotoxicity. Although the IL-6R antagonist tocilizumab is approved for treatment of CRS, there is no approved treatment of neurotoxicity associated with CD19-targeted CAR-T (CART19) cell therapy. Recent data suggest that monocytes and macrophages contribute to the development of CRS and neurotoxicity after CAR-T cell therapy. Therefore, we investigated neutralizing granulocyte-macrophage colony-stimulating factor (GM-CSF) as a potential strategy to manage CART19 cell-associated toxicities. In this study, we show that GM-CSF neutralization with lenzilumab does not inhibit CART19 cell function in vitro or in vivo. Moreover, CART19 cell proliferation was enhanced and durable control of leukemic disease was maintained better in patient-derived xenografts after GM-CSF neutralization with lenzilumab. In a patient acute lymphoblastic leukemia xenograft model of CRS and neuroinflammation (NI), GM-CSF neutralization resulted in a reduction of myeloid and T cell infiltration in the central nervous system and a significant reduction in NI and prevention of CRS. Finally, we generated GM-CSF-deficient CART19 cells through CRISPR/Cas9 disruption of GM-CSF during CAR-T cell manufacturing. These GM-CSFk/o CAR-T cells maintained normal functions and had enhanced antitumor activity in vivo, as well as improved overall survival, compared with CART19 cells. Together, these studies illuminate a novel approach to abrogate NI and CRS through GM-CSF neutralization, which may potentially enhance CAR-T cell function. Phase 2 studies with lenzilumab in combination with CART19 cell therapy are planned.

BMP-binding protein twisted gastrulation is required in mammary gland epithelium for normal ductal elongation and myoepithelial compartmentalization.

Bone morphogenetic proteins (BMPs) are involved in embryonic mammary gland (MG) development and can be dysregulated in breast cancer. However, the role BMPs play in the postnatal MG remains virtually unknown. BMPs are potent morphogens that are involved in cell fate determination, proliferation, apoptosis and adult tissue homeostasis. Twisted gastrulation (TWSG1) is a secreted BMP binding protein that modulates BMP ligand availability in the extracellular space. Here we investigate the consequences of TWSG1 deletion on development of the postnatal MG. At puberty, Twsg1 is expressed in the myoepithelium and in a subset of body cells of the terminal end buds. In the mature duct, Twsg1 expression is primarily restricted to the myoepithelial layer. Global deletion of Twsg1 leads to a delay in ductal elongation, reduced secondary branching, enlarged terminal end buds, and occluded lumens. This is associated with an increase in luminal epithelial cell number and a decrease in apoptosis. In the MG, pSMAD1/5/8 level and the expression of BMP target genes are reduced, consistent with a decrease in BMP signaling. GATA-3, which is required for luminal identity, is reduced in Twsg1(-/-) MGs, which may explain why K14 positive cells, which are normally restricted to the myoepithelial layer, are found within the luminal compartment and shed into the lumen. In summary, regulation of BMP signaling by TWSG1 is required for normal ductal elongation, branching of the ductal tree, lumen formation, and myoepithelial compartmentalization in the postnatal MG.

Autosomal dominant mesomandibular fibro-osseous dysplasia: a self-resolving inherited fibro-osseous lesion of the jaws.

A hereditary congenital condition characterized by a fibro-osseous lesion sharing some features with fibrous dysplasia and affecting the middle aspect of the mandible is presented. The condition was initially described as congenital monostotic fibrous dysplasia in two siblings, a male and a female. However, there is sufficient evidence that the disorder is autosomal dominant since it has been encountered in two of four children, both males, of the female propositus and one child, a boy, of the male propositus. All patients presented at birth or right after birth with enlargement of the middle part of the mandible. Radiographs from affected individuals have shown mesomandibular enlargement with irregular trabeculation akin of "ground-glass" appearance. Histologically, samples from all patients revealed woven bone proliferation in a cellular fibroblastic stroma. Interestingly, the originally described siblings, now in their 30s, have no evidence of jaw lesions either radiographically or clinically, thus indicating that the condition is self-limiting or self-resolving. An autosomal dominant mode of inheritance with apparent male predilection is favored. The molecular basis of this condition is currently unknown. However, the location of the lesions in the middle aspect of the mandible suggests dysregulation of Bone Morphogenetic Protein (BMP) signaling since BMPs regulate mandibular morphogenesis in utero, particularly in the medial region as well as postnatal bone remodeling. Immunohistochemical evaluation for a BMP-binding protein Twisted Gastrulation (TWSG1) revealed mosaic pattern of staining, with some cells, including osteoclasts, strongly stained and others exhibiting faint or no staining, thus supporting active regulation of BMP signaling within the lesion. Future investigations will determine if dysregulation of BMP signaling plays a causative role or rather reflects secondary activation of repair mechanisms and/or bone remodeling.

Twisted gastrulation expression in cholangiocellular and hepatocellular carcinoma.

AIMS: To assess the expression of Twisted gastrulation (TWSG1) protein, which regulates the activity of bone morphogenetic proteins (BMPs) in the extracellular space in malignant epithelial tumours of the liver. METHODS: Thirteen hepatocellular carcinoma (HCC) samples and 12 intrahepatic cholangiocellular carcinoma (CCA) samples were compiled into diagnosis-specific tissue microarrays. Sections were immunostained with a monoclonal antibody against TWSG1 and a polyclonal antibody against BMP4. Human cell lines were also used, including one HCC cell line (HepG2), three CCA cell lines (OZ, Huh-28, HuCCT-1) and a Papova-immortalised normal hepatocyte cell line (THLE-3) for western blot analysis (WBA). RESULTS: Immunostaining and WBA showed a stronger TWSG1 expression in CCA than in HCC. The difference in expression was significant (p<0.05), and the immunohistochemical signal was particularly evident in the malignant epithelial areas close to desmoplastic stroma in CCA and in the areas of glandular differentiation in HCC. No expression was seen in normal hepatocytes. Interestingly, BMP4 was fully expressed in CCA and only partly in HCC. WBA showed a band for BMP4 in both CCA and HCC cell lines. CONCLUSIONS: TWSG1 is expressed in both malignant epithelial carcinomas, although the level of expression is higher in CCA than in HCC and seems to correlate at least partially with BMP4 expression.

Glycosylation of Twisted Gastrulation is Required for BMP Binding and Activity during Craniofacial Development.

Twisted gastrulation (TWSG1) is a conserved, secreted glycoprotein that modulates signaling of bone morphogenetic proteins (BMPs) in the extracellular space. Deletion of exon 4 of mouse Twsg1 (mTwsg1) is associated with significant craniofacial defects. However, little is understood about the biochemical properties of the corresponding region of the protein. We have uncovered a significant role for exon 4 sequences as encoding the only two glycosylation sites of the mTWSG1 protein. Deletion of the entire exon 4 or mutation of both glycosylation sites within exon 4 abolishes glycosylation of mTWSG1. Importantly, we find that constructs with mutated glycosylation sites have significantly reduced BMP binding activity. We further show that glycosylation and activity of TWSG1 recombinant proteins vary markedly by cellular source. Non-glycosylated mTWSG1 made in E. coli has both reduced affinity for BMPs, as shown by surface plasmon resonance analysis, and reduced BMP inhibitory activity in a mandibular explant culture system compared to glycosylated proteins made in insect cells or murine myeloma cells. This study highlights an essential role for glycosylation in Twisted gastrulation action.