A B7-H4-Targeting Antibody-Drug Conjugate Shows Antitumor Activity in PARPi and Platinum-Resistant Cancers with B7-H4 Expression

PURPOSE

Platinum and PARP inhibitors (PARPi) demonstrate activity in breast and ovarian cancers, but drug resistance ultimately emerges. Here, we examine B7-H4 expression in primary and recurrent high-grade serous ovarian carcinoma (HGSOC) and the activity of a B7-H4-directed antibody-drug conjugate (B7-H4-ADC), using a pyrrolobenzodiazepine-dimer payload, in PARPi- and platinum-resistant HGSOC patient-derived xenograft (PDX) models.

EXPERIMENTAL DESIGN

B7-H4 expression was quantified by flow cytometry and IHC. B7-H4-ADC efficacy was tested against multiple cell lines in vitro and PDX in vivo. The effect of B7-H4-ADC on cell cycle, DNA damage, and apoptosis was measured using flow cytometry.

RESULTS

B7-H4 is overexpressed in 92% of HGSOC tumors at diagnosis (n = 12), persisted in recurrent matched samples after platinum treatment, and was expressed at similar levels across metastatic sites after acquired multi-drug resistance (n = 4). Treatment with B7-H4-ADC resulted in target-specific growth inhibition of multiple ovarian and breast cancer cell lines. In platinum- or PARPi-resistant ovarian cancer cells, B7-H4-ADC significantly decreased viability and colony formation while increasing cell-cycle arrest and DNA damage, ultimately leading to apoptosis. Single-dose B7-H4-ADC led to tumor regression in 65.5% of breast and ovarian PDX models (n = 29), with reduced activity in B7-H4 low or negative models. In PARPi and platinum-resistant HGSOC PDX models, scheduled B7-H4-ADC dosing led to sustained tumor regression and increased survival.

CONCLUSIONS

These data support B7-H4 as an attractive ADC target for treatment of drug-resistant HGSOC and provide evidence for activity of an ADC with a DNA-damaging payload in this population. See related commentary by Veneziani et al., p. 1434.

Comparison of the Clinicopathologic Features and T-Cell Infiltration of B7-H3 and B7-H4 Expression in Triple-negative Breast Cancer Subtypes

Previously we revealed an upregulated expression of B7-H3 and B7-H4 mRNA and protein in breast cancer, including triple-negative breast cancer (TNBC). However, little is known regarding the clinical impact and value of B7-H3 and B7-H4 in TNBC subtypes. Thus, this study evaluated the clinicopathologic effects of B7-H3 and B7-H4 mRNA and protein expression according to the TNBC subtypes. RNAscope in situ hybridization and immunohistochemistry of B7-H3 and B7-H4 was done for 186 TNBC samples using tissue microarray. Immunohistochemistry was also performed for TNBC molecular subtype-surrogate markers, CD3, and CD8. TNBCs were classified into basal-like (BL) (64.5%), luminal androgen receptor (10.8%), and unclassifiable (24.7%) subtypes. Tumor B7-H4 mRNA expression was associated with younger age at the initial diagnosis and with molecular TNBC subtypes. Expression of B7-H3 mRNA and protein in the tumor cells was negatively correlated with CD3+ and CD8+ T-cell infiltration density in the tumor and/or stromal region of TNBCs and their subtypes. High stromal B7-H3 mRNA expression was associated with poor disease-free and overall survival in the TNBCs and with overall survival in the unclassifiable subtype. Stromal B7-H3 mRNA expression was independently associated with overall survival and disease-free survival in the TNBCs and BL subtype, respectively. Our results indicate the importance of the stromal expression of B7-H3 mRNA as a prognostic factor in the TNBCs and BL subtype. The inverse relationship between B7-H3 expression and CD3+ and CD8+ T-lymphocyte infiltration represents a promising target for immunotherapy for the TNBCs, especially the BL subtype.

Does B7-H4 expression correlate with clinicopathologic characteristics and survival in ovarian cancer?: A systematic review and PRISMA-compliant meta-analysis

BACKGROUND

Several studies have shown that B7-H4 expression is significantly increased in ovarian cancer. However, the role of B7-H4 expression in ovarian cancer remains unclear, and some studies reporting conflicting results. A systematic review of the literature and meta-analysis were conducted to assess the clinicopathologic characteristics and prognostic significance of B7-H4 in ovarian cancer.

METHODS

Eligible studies were searched in the PubMed, MEDLINE, Cochrane Library, and the China National Knowledge Infrastructure databases. The included studies assessed the relationship between B7-H4 expression and clinicopathologic features or prognosis in patients with ovarian cancer through September 2017. A total of 1045 patients in 10 studies were included in the meta-analysis. Stata software version 12.0 was used to analyze the data. We used an odds ratio (OR) or hazard ratio (HR) with a 95% confidence interval (CI) to assess the risk or hazard association.

RESULTS

B7-H4 expression in ovarian cancer patients was significantly increased (OR: 4.20, 95% CI: 2.85-6.18, Z = 6.91, P < .05), and heterogeneity was low between studies (I = 8.2%, P = .366). With respect to the clinicopathologic features, no relation was detected between B7-H4 expression and International Federation of Gynaecology and Obstetricsstages stages (OR: 0.81, 95% CI: 0.64-1.03, Z = 1.70, P = .09), pathologic grade (OR: 0.91, 95% CI: 0.72-1.16, Z = 0.76, P = .45), tumor metastasis (OR: 1.25, 95% CI: 0.90-1.74, Z = 1.34, P = .18), or histologic type (OR: 1.17, 95% CI: 0.85-1.60, Z = 0.96, P = .34) in ovarian cancer. Furthermore, B7-H4 expression was significantly associated with a worse progression-free survival (PFS) (HR: 1.30, 95% CI: 1.17-1.45, Z = 4.79, P < .05).

CONCLUSION

B7-H4 expression was related to ovarian cancer, but not to patients' clinicopathologic characteristics. High B7-H4 expression was negatively correlated with survival outcome, suggesting that B7-H4 plays an essential role in poor prognosis in ovarian cancer patients.

The prognostic value of B7-H4 in pancreatic cancer: Systematic review and meta-analysis

BACKGROUND

There were many reports suggesting that different kinds of tumors can express B7-H4; however, the prognostic value in cancer was still unclearly. Therefore, we conducted a meta-analysis to investigate the relationship between overexpression of B7-H4 with the prognostic value in pancreatic cancer patients.

MATERIALS AND METHODS

The Pubmed, Embase, Cochrane Library, Ovid, Web of Science, and Chinese research database (including CBM, CNKI, and WAN FANG) were searched for related literature published until October 12, 2017. The pooled odds ratios (ORs) and/or pooled hazard ratios (HRs) for clinical pathological factors and overall survival (OS) were calculated and analyzed using Stata software. To assess whether an individual study had an impact on the result, sensitivity analysis was performed for all included individual studies using the fixed-effects model. Publication bias was evaluated using Egger's and Begg's tests.

RESULTS

Data from 6 observational studies including 442 patients were summarized in this meta-analysis, and each study was eligible for inclusion based on included and exclude criteria. The pooled results indicated that the B7-H4 overexpression could predict the presentation of lymph node metastasis (OR = 3.94, 95% CI: 1.22-12.66, P = .022), advanced TNM stage (T = the extent of the primary tumor, N = regional lymph nodes, M = distant metastases) (III+IV vs I+II; OR = 7.63, 95% CI: 2.46-23.66, P < .001), and the poor OS (HR = 3.00, 95%CI = 2.20-4.10, P < .001) in PC patients.

CONCLUSIONS

This study reveals that high expression of B7-H4 is an unfavorable prognostic factor for patients with pancreatic cancer. These results may guide the clinical management of this patient population.

Blockade of both B7-H4 and CTLA-4 co-signaling pathways enhances mouse islet allograft survival

Costimulation blockade is an effective way to prevent allograft rejection. In this study, we tested the efficacy of two negative co-signaling molecules in protecting islet allograft function. We used local expression of B7-H4 by adenoviral transduction of islets (Ad-B7-H4) and systemic administration of CTLA-4.Ig to investigate the outcomes of allograft survival. Five groups of streptozotocin-induced diabetic C57BL/6 mice received 400 islets each from BALB/c donors. The groups consisted of control (G1); CTLA-4.Ig (G2); Ad-LacZ (G3); Ad-B7-H4 (G4); and Ad-B7-H4 and CTLA-4.Ig combined (G5). G1 and G3 developed graft failure on average of two weeks. G2, G4 and G5 survived for 43.8 ± 34.8, 54.7 ± 31.2 and 77.8 ± 21.5 d, respectively. Activated T and B cells in the lymph nodes were significantly controlled by CTLA-4.Ig treatment. Significantly reduced infiltrates were also detected in the allografts of G2 compared with G1. By contrast, B7-H4 significantly inhibited Th1-associated IFN-gamma secretion in the early stage and increased Foxp3 (+) T cells in the long-term surviving allografts. Our study suggests that CTLA-4 and B7-H4 inhibit alloimmune responses through distinct mechanisms, and that combination therapy which activates two negative co-signaling pathways can further enhance islet allograft survival.

B7-H4 expression associates with cancer progression and predicts patient's survival in human esophageal squamous cell carcinoma

A retrospective cohort study including 112 patients suffering from esophageal squamous cell carcinoma (ESCC) was performed to investigate the expression of B7-H4 in ESCC and determine its association with patient's clinicopathological parameters and survival. Expression levels of B7-H4 on tumor cells and densities of tumor infiltrating lymphocytes (TILs) in the surgical specimens of ESCC tissues were characterized using immunohistochemical assays. Uni- and multivariate analyses were performed to evaluate the prognostic value of B7-H4 expression levels and densities of TILs in tumor sections. Positive B7-H4 immunostaining was observed in 107 of 112 (95.5%) of ESCC tissue sections. We further divided all patients into two major subgroups, a lower B7-H4 expression group with 46 patients and a higher B7-H4 expression group with 66 patients. We found that expression levels of B7-H4 on tumor cells were significantly correlated with patient's gender (P = 0.0288), distant metastasis (P = 0.0500), and TNM stage (P = 0.0258). Moreover, tumor cell B7-H4 expression was inversely correlated with densities of CD3(+) T cells in tumor nest (P = 0.0424) and CD8(+) T cells in tumor stroma (P = 0.0229). The overall survival rate of the patients with higher B7-H4 expression was significantly worse than that of the patients with lower B7-H4 expression (P = 0.0105, Hazard Ratio: 1.854, 95%CI:1.152-2.902). Markers of cell-mediated immune responses such as CD3, CD8, and T-bet were associated with better patient survival. The present study demonstrated that B7-H4 expression in human ESCC is associated with cancer progression, reduced tumor immunosurveillance and worse patient outcomes. B7-H4 can serve as a novel prognostic predictor for human ESCC and a potential target for the immune therapy against this malignancy.

B7-H4 mediates inhibition of T cell responses by activated murine hepatic stellate cells

Liver fibrosis is mediated by the transformation of hepatic stellate cells (HSC) from a quiescent to an activated state. To understand the role of HSC in liver immunity, we investigated the effect of this transition on T cell stimulation in vitro. Unlike quiescent HSC, activated HSC did not induce proliferation of antigen-specific T cells. Phenotypic analysis of quiescent and activated HSC revealed that activated HSC expressed the coinhibitory molecule B7-H4. Silencing B7-H4 by small interfering RNA (siRNA) in activated HSC restored the ability of T cells to proliferate, differentiate, and regain effector recall responses. Furthermore, expression of B7-H4 on HSC inhibits early T cell activation and addition of exogenous interleukin (IL)-2 reversed the T cell anergy induced by activated HSC.

CONCLUSION

These studies reveal a novel role for activated HSC in the attenuation of intrahepatic T cell responses by way of expression of the coinhibitory molecule B7-H4, and may provide fundamental insight into intrahepatic immunity during liver fibrogenesis.

Tumor expression of B7-H4 predicts poor survival of patients suffering from gastric cancer

To establish the prognostic value of B7-H4 expression by tumor cells in gastric cancer patients, we evaluated the association of B7-H4 expression with clinicopathologic factors and overall survival of gastric cancer patients. A retrospective cohort study including 156 gastric cancer patients was performed in the present report. Immunohistochemical assay was used to evaluate the expression of B7-H4 in the surgical specimens of gastric cancer tissues. Multi-univariate COX model was then used to evaluate the association of B7-H4 expression with the patients' survival and clinicopathological parameters. B7-H4 expression in the gastric cancer cells was observed in about 44.9% gastric cancer specimens. Univariate analysis demonstrated that there was no correlation between B7-H4 expression and sex, age, histological type, pathological grade or tumor size. In contrast, B7-H4 expression correlated positively with cancer invasiveness and lymph node metastasis. In addition, the median overall survival time of patients with lower B7-H4 expression was 13 months longer than that of patients with higher expression (chi(2) = 12.38, P < 0.0001), and the median disease-free survival time of patients with lower B7-H4 expression was significantly longer than that of patients with higher expression (33 vs. 16 months, chi(2) = 14.977, P < 0.0001). After adjustment for other confounding factors, the COX model analysis indicated that the death risk was significantly higher in patients with higher B7-H4 expression than those with lower expression (RR = 1.85, 95% CI = 1.15-2.96). The present study demonstrated that higher B7-H4 expression in cancer cells was associated with poor prognosis of gastric cancer patients. This is consistent with the idea that B7-H4 promotes cancer progression, likely via inhibition of anti-tumor immune responses.