From planned neck dissection to PET response to circulating tumour DNA: changes in post-treatment assessment of HPV-driven oropharyngeal cancer†.

INTRODUCTION: Circulating tumour human papillomavirus DNA (ctHPVDNA) is an emerging tool to assess post-treatment response in patients with HPV+ oropharyngeal squamous cell carcinoma (OPSCC). Its use is not a standard practice, however, with interval F-18 FDG PET/CT and fiberoptic examination preferred. Post-treatment PET/CT at 3 months has a low positive predictive value (PPV), especially in patients with HPV+ OPSCC treated with (chemo)radiation therapy (CRT). We aimed to compare 3-6 month post-treatment PET/CT and ctHPVDNA test results to determine the most effective option for post-treatment response assessment. METHODS: Patients with HPV+ OPSCC that underwent commercially available ctHPVDNA blood testing after curative intent treatment were identified. Demographic, clinical, treatment, surveillance and oncologic outcome information were collected for each patient. Specificity and false positive rate were calculated for post-treatment PET/CT and ctHPVDNA. RESULTS: 80% of patients had Stage I disease. 52% of the population was treated with definitive chemoradiation (43%) or accelerated radiation (9%), with the remaining patients treated with transoral robotic surgery (TORS) +/- risk-adapted adjuvant therapy. In total, 25 patients underwent ctHPVDNA testing and PET/CT at 3-6 months after finishing treatment. At 3-6 months post-treatment, specificity of ctHPVDNA and PET/CT was 96% and 56%, correlating to false positive rates of 4% and 44%, respectively. CONCLUSIONS: ctHPVDNA is more reliable than PET/CT following treatment in patients with HPV+ OPSCC, and its incorporation in post-treatment response assessment will decrease the rate of anxiety over persistent disease and lead to a decrease in unnecessary medical procedures, including completion of neck dissection.

The multidisciplinary management of cholangiocarcinoma.

Cholangiocarcinoma is a lethal malignancy of the biliary epithelium that can arise anywhere along the biliary tract. Surgical resection confers the greatest likelihood of long-term survivability. However, its insidious onset, difficult diagnostics, and resultant advanced presentation render the majority of patients unresectable, highlighting the importance of early detection with novel biomarkers. Developing liver-directed therapies and emerging targeted therapeutics may offer improved survivability for patients with unresectable or advanced disease. In this article, the authors review the current multidisciplinary standards of care in resectable and unresectable cholangiocarcinoma, with an emphasis on novel biomarkers for early detection and nonsurgical locoregional therapy options.

The immune checkpoint B7x expands tumor-infiltrating Tregs and promotes resistance to anti-CTLA-4 therapy.

Immune checkpoint molecules play critical roles in regulating the anti-tumor immune response, and tumor cells often exploit these pathways to inhibit and evade the immune system. The B7-family immune checkpoint B7x is widely expressed in a broad variety of cancer types, and is generally associated with advanced disease progression and poorer clinical outcomes, but the underlying mechanisms are unclear. Here, we show that transduction and stable expression of B7x in multiple syngeneic tumor models leads to the expansion of immunosuppressive regulatory T cells (Tregs). Mechanistically, B7x does not cause increased proliferation of Tregs in tumors, but instead promotes the conversion of conventional CD4+ T cells into Tregs. Further, we find that B7x induces global transcriptomic changes in Tregs, driving these cells to adopt an activated and suppressive phenotype. B7x increases the expression of the Treg-specific transcription factor Foxp3 in CD4+ T cells by modulating the Akt/Foxo pathway. B7x-mediated regulation of Tregs reduces the efficacy of anti-CTLA-4 treatment, a therapeutic that partially relies on Treg-depletion. However, combination treatment of anti-B7x and anti-CTLA-4 leads to synergistic therapeutic efficacy and overcomes the B7x-mediated resistance to anti-CTLA-4. Altogether, B7x mediates an immunosuppressive Treg-promoting pathway within tumors and is a promising candidate for combination immunotherapy.

Vitamin D Supplementation in COVID-19 Patients: A Clinical Case Series.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has infected more than 4.4 million people and caused more than 300,000 deaths partly through acute respiratory distress syndrome with propensity to affect African American and Hispanic communities disproportionately. Patients with worse outcomes have exhibited higher blood plasma levels of proinflammatory cytokines. Activation of the vitamin D receptor expressed on immune cells has been shown to directly reduce the secretion of inflammatory cytokines, such as interleukin-6, and indirectly affect C-reactive protein. AREAS OF UNCERTAINTY: The significance of the vitamin D pathway in patients diagnosed with COVID-19. THERAPEUTIC INNOVATION: Vitamin D supplementation in patients after diagnosis of COVID-19. PATIENTS AND PHARMACOLOGICAL INTERVENTIONS: We report 4 vitamin D deficient patients diagnosed with COVID-19 in April 2020 who were provided with either cholecalciferol of 1000 IU daily (standard dose) or ergocalciferol 50,000 IU daily for 5 days (high dose) as part of supplementation. CLINICAL OUTCOMES: Patients that received a high dose of vitamin D supplementation achieved normalization of vitamin D levels and improved clinical recovery evidenced by shorter lengths of stay, lower oxygen requirements, and a reduction in inflammatory marker status. CONCLUSIONS: Vitamin D supplementation may serve as a viable alternative for curtailing acute respiratory distress syndrome in patients in underserved communities where resources to expensive and sought-after medications may be scarce. Randomized clinical trials will serve as an appropriate vessel to validate the efficacy of the therapeutic regimen and dissection of the pathway.

NF-κB RelA renders tumor-associated macrophages resistant to and capable of directly suppressing CD8+ T cells for tumor promotion.

Activation of the inflammatory transcription factor NF-κB in tumor-associated macrophages (TAMs) is assumed to contribute to tumor promotion. However, whether and how NF-κB drives the antitumor macrophages to become pro-tumorigenic have not been determined in any cancer type yet. Similarly, how TAMs repress CD8+ cytotoxic T lymphocytes (CTLs) remains largely unknown, although their importance in regulatory T (Treg) cell regulation and tumor promotion has been well appreciated. Here, using an endogenous lung cancer model we uncover a direct crosstalk between TAMs and CTLs. TAMs suppress CTLs through the T-cell inhibitory molecule B7x (B7-H4/B7S1) in a cell-cell contact manner, whereas CTLs kill TAMs in a tumor antigen-specific manner. Remarkably, TAMs secrete the known T-cell suppressive cytokine interleukin-10 (IL-10) to activate, but not to repress, CTLs. Notably, one major role of cell-intrinsic NF-κB RelA is to drive TAMs to suppress CTLs for tumor promotion. It induces B7x expression in TAMs directly, and restricts IL-10 expression indirectly by repressing expression of the NF-κB cofactor Bcl3 and subsequent Bcl3/NF-κB1-mediated transcription of IL-10. It also renders TAMs resistant to CTLs by up-regulating anti-apoptotic genes. These studies help understand how immunity is shaped in lung tumorigenesis, and suggest a RelA-targeted immunotherapy for this deadliest cancer.

Tumor-expressed immune checkpoint B7x promotes cancer progression and antigen-specific CD8 T cell exhaustion and suppressive innate immune cells.

B7x (B7-H4 or B7S1) is a coinhibitory member of the B7 immune checkpoint ligand family that regulates immune function following ligation with its unknown cognate receptors. B7x has limited expression on normal tissues, but is up-regulated on solid human tumors to inhibit anti-tumor immunity and associates with poor clinical prognosis. We assessed the contribution of cytokine stimuli to induce surface B7x expression on cancer cells and the role of tumor-expressed B7x in a murine pulmonary metastasis model, and finally evaluated the potential interaction between B7x and Neuropilin-1, a suggested potential cognate receptor. We showed that pro-inflammatory and anti-inflammatory cytokines IFNγ, TNFα, and IL-10 did not induce expression of B7x on human or murine cancer cells. Following i.v. injection of CT26, a murine colon cancer cell line in the BALB/c background, we observed a significant increase in tumor burden in the lung of B7x-expressing CT26 mice compared to B7x-negative parental CT26 control mice. This was marked by a significant increase in M2 tumor associated macrophages and antigen-specific CD8 T cell exhaustion. Finally, we found through multiple systems that there was no evidence for B7x and Neuropilin-1 direct interaction. Thus, the B7x pathway has an essential role in modulating the innate and adaptive immune cell infiltrate in the tumor microenvironment with its currently unknown cognate receptor(s).

Molecular Pathways: Targeting B7-H3 (CD276) for Human Cancer Immunotherapy.

B7-H3 (CD276) is an important immune checkpoint member of the B7 and CD28 families. Induced on antigen-presenting cells, B7-H3 plays an important role in the inhibition of T-cell function. Importantly, B7-H3 is highly overexpressed on a wide range of human solid cancers and often correlates with both negative prognosis and poor clinical outcome in patients. Challenges remain to identify the receptor(s) of B7-H3 and thus better elucidate the role of the B7-H3 pathway in immune responses and tumor evasion. With a preferential expression on tumor cells, B7-H3 is an attractive target for cancer immunotherapy. Based on the clinical success of inhibitory immune checkpoint blockade (CTLA-4, PD-1, and PD-L1), mAbs against B7-H3 appear to be a promising therapeutic strategy worthy of development. An unconventional mAb against B7-H3 with antibody-dependent cell-mediated cytotoxicity is currently being evaluated in a phase I clinical trial and has shown encouraging preliminary results. Additional therapeutic approaches in targeting B7-H3, such as blocking mAbs, bispecific mAbs, chimeric antigen receptor T cells, small-molecule inhibitors, and combination therapies, should be evaluated, as these technologies have already shown positive results in various cancer settings. A better understanding of the B7-H3 pathway in humans will surely help to further optimize associated cancer immunotherapies. Clin Cancer Res; 22(14); 3425-31. ©2016 AACR.

ZEB1 Mediates Acquired Resistance to the Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer.

Epithelial-mesenchymal transition (EMT) is one mechanism of acquired resistance to inhibitors of the epidermal growth factor receptor-tyrosine kinases (EGFR-TKIs) in non-small cell lung cancer (NSCLC). The precise mechanisms of EMT-related acquired resistance to EGFR-TKIs in NSCLC remain unclear. We generated erlotinib-resistant HCC4006 cells (HCC4006ER) by chronic exposure of EGFR-mutant HCC4006 cells to increasing concentrations of erlotinib. HCC4006ER cells acquired an EMT phenotype and activation of the TGF-ß/SMAD pathway, while lacking both T790M secondary EGFR mutation and MET gene amplification. We employed gene expression microarrays in HCC4006 and HCC4006ER cells to better understand the mechanism of acquired EGFR-TKI resistance with EMT. At the mRNA level, ZEB1 (TCF8), a known regulator of EMT, was >20-fold higher in HCC4006ER cells than in HCC4006 cells, and increased ZEB1 protein level was also detected. Furthermore, numerous ZEB1 responsive genes, such as CDH1 (E-cadherin), ST14, and vimentin, were coordinately regulated along with increased ZEB1 in HCC4006ER cells. We also identified ZEB1 overexpression and an EMT phenotype in several NSCLC cells and human NSCLC samples with acquired EGFR-TKI resistance. Short-interfering RNA against ZEB1 reversed the EMT phenotype and, importantly, restored erlotinib sensitivity in HCC4006ER cells. The level of micro-RNA-200c, which can negatively regulate ZEB1, was significantly reduced in HCC4006ER cells. Our results suggest that increased ZEB1 can drive EMT-related acquired resistance to EGFR-TKIs in NSCLC. Attempts should be made to explore targeting ZEB1 to resensitize TKI-resistant tumors.

Expression, Clinical Significance, and Receptor Identification of the Newest B7 Family Member HHLA2 Protein.

PURPOSE: HHLA2 (B7H7/B7-H5/B7y) is a newly identified B7 family member that regulates human T-cell functions. However, its protein expression in human organs and significance in human diseases are unknown. The objective of this study was to analyze HHLA2 protein expression in normal human tissues and cancers, as well as its prognostic significance, to explore mechanisms regulating HHLA2 expression, and to identify candidate HHLA2 receptors. EXPERIMENTAL DESIGN: An immunohistochemistry protocol and a flow cytometry assay with newly generated monoclonal antibodies were developed to examine HHLA2 protein. HHLA2 gene copy-number variation was analyzed from cancer genomic data. The combination of bioinformatics analysis and immunologic approaches was established to explore HHLA2 receptors. RESULTS: HHLA2 protein was detected in trophoblastic cells of the placenta and the epithelium of gut, kidney, gallbladder, and breast, but not in most other organs. In contrast, HHLA2 protein was widely expressed in human cancers from the breast, lung, thyroid, melanoma, pancreas, ovary, liver, bladder, colon, prostate, kidney, and esophagus. In a cohort of 50 patients with stage I-III triple-negative breast cancer, 56% of patients had aberrant expression of HHLA2 on their tumors, and high HHLA2 expression was significantly associated with regional lymph node metastasis and stage. The Cancer Genome Atlas revealed that HHLA2 copy-number gains were present in 29% of basal breast cancers, providing a potential mechanism for increased HHLA2 protein expression in breast cancer. Finally, Transmembrane and Immunoglobulin Domain Containing 2 (TMIGD2) was identified as one of the receptors for HHLA2. CONCLUSIONS: Wide expression of HHLA2 in human malignancies, together with its association with poor prognostic factors and its T-cell coinhibitory capability, suggests that the HHLA2 pathway represents a novel immunosuppressive mechanism within the tumor microenvironment and an attractive target for human cancer therapy.

Human cancer immunotherapy with antibodies to the PD-1 and PD-L1 pathway.

The programmed death 1 (PD-1) receptor and its ligands programmed death ligand 1 (PD-L1) and PD-L2, members of the CD28 and B7 families, play critical roles in T cell coinhibition and exhaustion. Overexpression of PD-L1 and PD-1 on tumor cells and tumor-infiltrating lymphocytes, respectively, correlates with poor disease outcome in some human cancers. Monoclonal antibodies (mAbs) blockading the PD-1/PD-L1 pathway have been developed for cancer immunotherapy via enhancing T cell functions. Clinical trials with mAbs to PD-1 and PD-L1 have shown impressive response rates in patients, particularly for melanoma, non-small-cell lung cancer (NSCLC), renal cell carcinoma (RCC), and bladder cancer. Further studies are needed to dissect the mechanisms of variable response rate, to identify biomarkers for clinical response, to develop small-molecule inhibitors, and to combine these treatments with other therapies.

Structure and cancer immunotherapy of the B7 family member B7x.

B7x (B7-H4 or B7S1) is a member of the B7 family that can inhibit T cell function. B7x protein is absent in most normal human tissues and immune cells, but it is overexpressed in human cancers and often correlates with negative clinical outcome. The expression pattern and function of B7x suggest that it may be a potent immunosuppressive pathway in human cancers. Here, we determined the crystal structure of the human B7x immunoglobulin variable (IgV) domain at 1.59 Å resolution and mapped the epitopes recognized by monoclonal antibodies. We developed an in vivo system to screen therapeutic monoclonal antibodies against B7x and found that the clone 1H3 significantly inhibited growth of B7x-expressing tumors in vivo via multiple mechanisms. Furthermore, the surviving mice given 1H3 treatment were resistant to tumor rechallenge. Our data suggest that targeting B7x on tumors is a promising cancer immunotherapy and humanized 1H3 may be efficacious for immunotherapy of human cancers.

B7x and myeloid-derived suppressor cells in the tumor microenvironment: A tale of two cities.

A new study demonstrates the tumorigenic functions of B7x and reveals a link between B7x and myeloid-derived suppressor cells (MDSCs) within the tumor microenvironment. We propose that the binding of B7x to a hitherto unidentified receptor on MDSCs may stimulate their proliferation and/or immunosuppressive functions, hence promoting tumor growth.

HHLA2 is a member of the B7 family and inhibits human CD4 and CD8 T-cell function.

T-cell costimulation and coinhibition generated by engagement of the B7 family and their receptor CD28 family are of central importance in regulating the T-cell response, making these pathways very attractive therapeutic targets. Here we describe HERV-H LTR-associating protein 2 (HHLA2) as a member of the B7 family that shares 10-18% amino acid identity and 23-33% similarity to other human B7 proteins and phylogenetically forms a subfamily with B7x and B7-H3 within the family. HHLA2 is expressed in humans but not in mice, which is unique within the B7 and CD28 families. HHLA2 protein is constitutively expressed on the surface of human monocytes and is induced on B cells after stimulation with LPS and IFN-γ. HHLA2 does not interact with other known members of the CD28 family or the B7 family, but does bind a putative receptor that is constitutively expressed not only on resting and activated CD4 and CD8 T cells but also on antigen-presenting cells. HHLA2 inhibits proliferation of both CD4 and CD8 T cells in the presence of T-cell receptor signaling. In addition, HHLA2 significantly reduces cytokine production by T cells including IFN-γ, TNF-α, IL-5, IL-10, IL-13, IL-17A, and IL-22. Thus, we have identified a unique B7 pathway that is able to inhibit human CD4 and CD8 T-cell proliferation and cytokine production. This unique human T-cell coinhibitory pathway may afford unique strategies for the treatment of human cancers, autoimmune disorders, infection, and transplant rejection and may help to design better vaccines.

Host b7x promotes pulmonary metastasis of breast cancer.

B7x (B7-H4 or B7S1) is an inhibitory member of the B7 family of T cell costimulation. It is expressed in low levels in healthy peripheral tissues, such as the lung epithelium, but is overexpressed in a variety of human cancers with negative clinical associations, including metastasis. However, the function of B7x in the context of cancer, whether expressed on cancer cells or on surrounding "host" tissues, has not been elucidated in vivo. We used the 4T1 metastatic breast cancer model and B7x knockout (B7x (-/-)) mice to investigate the effect of host tissue-expressed B7x on cancer. We found that 4T1 cells were B7x negative in vitro and in vivo, and B7x(-/-) mice had significantly fewer lung 4T1 tumor nodules than did wild-type mice. Furthermore, B7x(-/-) mice showed significantly enhanced survival and a memory response to tumor rechallenge. Mechanistic studies revealed that the presence of B7x correlated with reduced general and tumor-specific T cell cytokine responses, as well as with an increased infiltration of immunosuppressive cells, including tumor-associated neutrophils, macrophages, and regulatory T cells, into tumor-bearing lungs. Importantly, tumor-associated neutrophils strongly bound B7x protein and inhibited the proliferation of both CD4 and CD8 T cells. These results suggest that host B7x may enable metastasizing cancer cells to escape local antitumor immune responses through interactions with the innate and adaptive immune systems. Thus, targeting the B7x pathway holds much promise for improving the efficacy of immunotherapy for metastatic cancer.