Multiscale imaging of therapeutic anti-PD-L1 antibody localization using molecularly defined imaging agents

BACKGROUND

While immune checkpoint inhibitors such as anti-PD-L1 antibodies have revolutionized cancer treatment, only subgroups of patients show durable responses. Insight in the relation between clinical response, PD-L1 expression and intratumoral localization of PD-L1 therapeutics could improve patient stratification. Therefore, we present the modular synthesis of multimodal antibody-based imaging tools for multiscale imaging of PD-L1 to study intratumoral distribution of PD-L1 therapeutics.

RESULTS

To introduce imaging modalities, a peptide containing a near-infrared dye (sulfo-Cy5), a chelator (DTPA), an azide, and a sortase-recognition motif was synthesized. This peptide and a non-fluorescent intermediate were used for site-specific functionalization of c-terminally sortaggable mouse IgG1 (mIgG1) and Fab anti-PD-L1. To increase the half-life of the Fab fragment, a 20 kDa PEG chain was attached via strain-promoted azide-alkyne cycloaddition (SPAAC). Biodistribution and imaging studies were performed with 111In-labeled constructs in 4T1 tumor-bearing mice. Comparing our site-specific antibody-conjugates with randomly conjugated antibodies, we found that antibody clone, isotype and method of DTPA conjugation did not change tumor uptake. Furthermore, addition of sulfo-Cy5 did not affect the biodistribution. PEGylated Fab fragment displayed a significantly longer half-life compared to unPEGylated Fab and demonstrated the highest overall tumor uptake of all constructs. PD-L1 in tumors was clearly visualized by SPECT/CT, as well as whole body fluorescence imaging. Immunohistochemistry staining of tumor sections demonstrated that PD-L1 co-localized with the fluorescent and autoradiographic signal. Intratumoral localization of the imaging agent could be determined with cellular resolution using fluorescent microscopy.

CONCLUSIONS

A set of molecularly defined multimodal antibody-based PD-L1 imaging agents were synthesized and validated for multiscale monitoring of PD-L1 expression and localization. Our modular approach for site-specific functionalization could easily be adapted to other targets.

High hepatocyte growth factor expression in primary tumor predicts better overall survival in male breast cancer

BACKGROUND

Breast cancer is rare in men, but management is focused on tumor characteristics commonly found in female breast cancer. The tumor microenvironment of male breast cancer is less well understood, and insight may improve male breast cancer management. The hepatocyte growth factor (HGF)/c-MET axis and the stromal cell-derived factor-1 (CXCL12)/C-X-C chemokine receptor type 4 (CXCR4) axis are prognostic in women with breast cancer. We aimed to investigate these factors in male breast cancer and correlate them with patient survival.

METHODS

From 841 Dutch males with breast cancer who were enrolled in the EORTC 10085/TBCRC/BIG/NABCG International Male Breast Cancer Program (NCT01101425) and diagnosed between 1990 and 2010, archival primary tumor samples were collected. Tissue microarrays were constructed with 3 cores per sample and used for immunohistochemical analysis of HGF, c-MET, CXCL12, and CXCR4. Overall survival (OS) of the patients without metastases (M0) was analyzed using the Kaplan-Meier method. The value of the markers regarding OS was determined using univariable and multivariable Cox regression analyses, providing hazard ratios (HRs) and 95% confidence intervals (95% CIs).

RESULTS

Of 720 out of 841 patients, sufficient tissue was available for analysis; 487 out of 720 patients had M0 disease. Patients with high HGF expression and high CXCL12 expression had a superior OS (low vs high expression of both markers, 7.5 vs 13.0 years, hazard ratio [HR] 0.64, 95% CI 0.49-0.84, P = 0.001 [HGF]; 9.1 vs 15.3 years, HR 0.63, 95% CI 0.45-0.87, P = 0.005 [CXCL12]). Multivariate analysis identified HGF as an independent predictor for OS (HR 0.64, 95% CI 0.47-0.88, P = 0.001).

CONCLUSIONS

HGF and CXCL12 tumor expression appear to identify male breast cancer patients with a relatively good prognosis. Possibly, this could support male breast cancer-specific management strategies in the future.

Laparoscopic detection and resection of occult liver tumors of multiple cancer types using real-time near-infrared fluorescence guidance

BACKGROUND

Tumor recurrence after radical resection of hepatic tumors is not uncommon, suggesting that malignant lesions are missed during surgery. Intraoperative navigation using fluorescence guidance is an innovative technique enabling real-time identification of (sub)capsular liver tumors. The objective of the current study was to compare fluorescence imaging (FI) and conventional imaging modalities for laparoscopic detection of both primary and metastatic tumors in the liver.

METHODS

Patients undergoing laparoscopic resection of a malignant hepatic tumor were eligible for inclusion. Patients received standard of care, including preoperative CT and/or MRI. In addition, 10 mg indocyanine green was intravenously administered 1 day prior to surgery. After introduction of the laparoscope, inspection, FI, and laparoscopic ultrasonography (LUS) were performed. Histopathological examination of resected suspect tissue was considered the gold standard.

RESULTS

Twenty-two patients suspected of having hepatocellular carcinoma (n = 4), cholangiocarcinoma (n = 2) or liver metastases from colorectal carcinoma (n = 12), uveal melanoma (n = 2), and breast cancer (n = 2) were included. Two patients were excluded because their surgery was unexpectedly postponed several days. Twenty-six malignancies were resected in the remaining 20 patients. Sensitivity for various modalities was 80 % (CT), 84 % (MRI), 62 % (inspection), 86 % (LUS), and 92 % (FI), respectively. Three metastases (12 %) were identified solely by FI. All 26 malignancies could be detected by combining LUS and FI (100 % sensitivity).

CONCLUSION

This study demonstrates added value of FI during laparoscopic resections of several hepatic tumors. Although larger series will be needed to confirm long-term patient outcome, the technology already aids the surgeon by providing real-time fluorescence guidance.