Minhyung Kim

Intraoperative intravital microscopy permits the study of human tumour vessels.

Tumour vessels have been studied extensively as they are critical sites for drug delivery, anti-angiogenic therapies and immunotherapy. As a preclinical tool, intravital microscopy (IVM) allows for in vivo real-time direct observation of vessels at the cellular level. However, to date there are no reports of intravital high-resolution imaging of human tumours in the clinical setting. Here we report the feasibility of IVM examinations of human malignant disease with an emphasis on tumour vasculature as the major site of tumour-host interactions. Consistent with preclinical observations, we show that patient tumour vessels are disorganized, tortuous and ∼50% do not support blood flow. Human tumour vessel diameters are larger than predicted from immunohistochemistry or preclinical IVM, and thereby have lower wall shear stress, which influences delivery of drugs and cellular immunotherapies. Thus, real-time clinical imaging of living human tumours is feasible and allows for detection of characteristics within the tumour microenvironment.

Tumor-induced MDSC act via remote control to inhibit L-selectin-dependent adaptive immunity in lymph nodes

Myeloid-derived suppressor cells (MDSC) contribute to an immunosuppressive network that drives cancer escape by disabling T cell adaptive immunity. The prevailing view is that MDSC-mediated immunosuppression is restricted to tissues where MDSC co-mingle with T cells. Here we show that splenic or, unexpectedly, blood-borne MDSC execute far-reaching immune suppression by reducing expression of the L-selectin lymph node (LN) homing receptor on naïve T and B cells. MDSC-induced L-selectin loss occurs through a contact-dependent, post-transcriptional mechanism that is independent of the major L-selectin sheddase, ADAM17, but results in significant elevation of circulating L-selectin in tumor-bearing mice. Even moderate deficits in L-selectin expression disrupt T cell trafficking to distant LN. Furthermore, T cells preconditioned by MDSC have diminished responses to subsequent antigen exposure, which in conjunction with reduced trafficking, severely restricts antigen-driven expansion in widely-dispersed LN. These results establish novel mechanisms for MDSC-mediated immunosuppression that have unanticipated implications for systemic cancer immunity. DOI: http://dx.doi.org/10.7554/eLife.17375.001

Immune Adjuvant Activity of Pre-Resectional Radiofrequency Ablation Protects against Local and Systemic Recurrence in Aggressive Murine Colorectal Cancer

Purpose While surgical resection is a cornerstone of cancer treatment, local and distant recurrences continue to adversely affect outcome in a significant proportion of patients. Evidence that an alternative debulking strategy involving radiofrequency ablation (RFA) induces antitumor immunity prompted the current investigation of the efficacy of performing RFA prior to surgical resection (pre-resectional RFA) in a preclinical mouse model. Experimental Design Therapeutic efficacy and systemic immune responses were assessed following pre-resectional RFA treatment of murine CT26 colon adenocarcinoma. Results Treatment with pre-resectional RFA significantly delayed tumor growth and improved overall survival compared to sham surgery, RFA, or resection alone. Mice in the pre-resectional RFA group that achieved a complete response demonstrated durable antitumor immunity upon tumor re-challenge. Failure to achieve a therapeutic benefit in immunodeficient mice confirmed that tumor control by pre-resectional RFA depends on an intact adaptive immune response rather than changes in physical parameters that make ablated tumors more amenable to a complete surgical excision. RFA causes a marked increase in intratumoral CD8+ T lymphocyte infiltration, thus substantially enhancing the ratio of CD8+ effector T cells: FoxP3+ regulatory T cells. Importantly, pre-resectional RFA significantly increases the number of antigen-specific CD8+ T cells within the tumor microenvironment and tumor-draining lymph node but had no impact on infiltration by myeloid-derived suppressor cells, M1 macrophages or M2 macrophages at tumor sites or in peripheral lymphoid organs (i.e., spleen). Finally, pre-resectional RFA of primary tumors delayed growth of distant tumors through a mechanism that depends on systemic CD8+ T cell-mediated antitumor immunity. Conclusion Improved survival and antitumor systemic immunity elicited by pre-resectional RFA support the translational potential of this neoadjuvant treatment for cancer patients with high-risk of local and systemic recurrence.

The benefit of intraperitoneal chemotherapy for the treatment of colorectal carcinomatosis

The clinical practice of hyperthermic intraperitoneal chemoperfusion (HIPEC) for carcinomatosis has lacked preclinical justification. A standardized mouse model was created to evaluate the independent effects of intraperitoneal chemotherapy. Diffuse colorectal carcinomatosis was generated in mice prior to intraperitoneal lavage with mitomycin C (MMC) at clinically comparable dosing for variable lengths of time. Tumor volumes, MMC tissue concentrations and survival were measured in comparison to saline lavage and intravenous MMC. Magnetic resonance imaging revealed a direct correlation between tumor volume, MMC dose and exposure time and survival. Intravenous MMC demonstrated a rapid clearance from the blood, lower peritoneal tissue concentrations, less tumor growth inhibition and decreased survival compared to intraperitoneal administration. Intraperitoneal chemotherapy inhibited tumor growth independent of cytoreduction or hyperthermia, demonstrated improved peritoneal tissue concentration and was associated with increased survival. These data support the clinical utility of the intraperitoneal chemotherapy component of HIPEC.

A novel mouse model of isolated limb perfusion for extremity melanoma

BACKGROUND Isolated limb perfusion (ILP) for extremity melanoma has been used clinically for over half a century. Mouse modeling of ILP may offer significant experimental advantages compared with existing models. We propose a novel mouse model and report our initial experience. METHODS We injected female C57BL/6 mice (22-25 g) with 1 × 10(6) B16 melanoma cells subcutaneously in the distal right thigh. After 7 d of tumor establishment, we cannulated the superficial femoral artery (inflow) and vein (outflow) of anesthetized mice and placed a proximal tourniquet. Non-oxygenated perfusate included low-dose or high-dose melphalan and saline (control). We analyzed endpoints of cannulation time, procedural complications, morbidity, toxicity, and tumor response. RESULTS We performed 11 superficial femoral vessel cannulations. Median cannulation time was 19 min (range, 15-32 min). Intact perfusion models were obtained in 10 of 11 cases (91%); one case failed owing to superficial femoral vein dissection. Morbidity rate was 20% (one wound dehiscence and one hematoma). Both high- and low-dose melphalan perfusion groups (4 mice/group) trended to growth delay and regression compared with saline-perfused groups. Toxicity was greater in the high-dose melphalan-treated mice. CONCLUSIONS We have established the first reproducible mouse model of ILP for melanoma. Future experiments will take advantage of the large number of established mouse knockout models and reagents to dissect the precise mechanisms of tumor control after ILP, and examine to novel agents.

A murine model of targeted infusion for intracranial tumors

Historically, intra-arterial (IA) drug administration for malignant brain tumors including glioblastoma multiforme (GBM) was performed as an attempt to improve drug delivery. With the advent of percutaneous neuorovascular techniques and modern microcatheters, intracranial drug delivery is readily feasible; however, the question remains whether IA administration is safe and more effective compared to other delivery modalities such as intravenous (IV) or oral administrations. Preclinical large animal models allow for comparisons between treatment routes and to test novel agents, but can be expensive and difficult to generate large numbers and rapid results. Accordingly, we developed a murine model of IA drug delivery for GBM that is reproducible with clear readouts of tumor response and neurotoxicities. Herein, we describe a novel mouse model of IA drug delivery accessing the internal carotid artery to treat ipsilateral implanted GBM tumors that is consistent and reproducible with minimal experience. The intent of establishing this unique platform is to efficiently interrogate targeted anti-tumor agents that may be designed to take advantage of a directed, regional therapy approach for brain tumors.

Novel mouse models of hepatic artery infusion

BACKGROUND The liver has unique anatomy in that most blood flow to normal hepatocytes is derived from the portal venous system, whereas liver tumors obtain their nutrient blood supply exclusively from the hepatic artery. The focused arterial delivery of anticancer agents to liver tumors has been performed for decades; however, preclinical models to standardize drug regimens and examine novel agents have been lacking. The purpose of this study was to establish preclinical hepatic artery infusion (HAI) models in a mouse and to evaluate the safety and delivery capability of the models. MATERIAL AND METHODS C57BL/6 and BALB/c mice were used to develop models of HAI via the hepatic artery (HA), superior pancreaticoduodenal artery (SPDA), or lienogastric artery (LGA). Success rates, distribution of perfusion, and associated morbidity and mortality were analyzed between groups. RESULTS All three models were feasible and reproducible in mice, and there was no statistical difference on body weight change between models. The HA model had a 13.3% mortality from acute liver failure, and the SPDA model demonstrated duodenal and pancreatic toxicity. SPDA and LGA routes had the highest success rates (96.7% and 91.4%, respectively) with low mortality, better drug delivery, and preserved physiologic liver function compared with the HA model. CONCLUSIONS The optimal route of HAI was mouse breed specific; SPDA access in BALB/c mice, and the LGA access in C57BL/6 mice. The described techniques serve as a reproducible platform for the identification and characterization of therapeutics for diverse metastatic liver tumors.

Preclinical Validation of a Single-Treatment Infusion Modality That Can Eradicate Extremity Melanomas

Isolated limb perfusion (ILP) with the chemotherapeutic agent melphalan is an effective treatment option for extremity in-transit melanoma but is toxic and technically challenging to deliver locoregionally. CBL0137 is an experimental clinical drug with broad anticancer activity in animal models, owing to its ability to bind DNA in a nongenotoxic manner and inactivate the FACT chromatin modulator essential for tumor cell viability. Here, we report that CBL0137 delivered by ILP in a murine melanoma model is as efficacious as melphalan, displaying antitumor activity at doses corresponding to only a fraction of the systemic MTD of CBL0137. The ability to bind DNA quickly combined with a favorable safety profile made it possible to substitute CBL0137 in the ILP protocol, using an intra-arterial infusion method, to safely achieve effective tumor suppression. Our findings of a preclinical proof of concept for CBL0137 and its administration via intra-arterial infusion as a superior treatment compared with melphalan ILP allows for locoregional treatment anywhere a catheter can be placed. Cancer Res; 76(22); 6620-30. ©2016 AACR.

Abstract 4225: Dynamic control of tumor vasculature with direct observation using intravital microscopy

Introduction Intravital microscopy (IVM) provides in vivo real-time imaging of tumor-associated vasculature. Our group was the first to use IVM successfully in human subjects to image melanoma associated vessels. In this preclinical study, we hypothesized that intravenous (IV) nicardipine increases observable blood flow to tumor through vasodilatation and therefore may facilitate drug delivery. Methods Standard window chambers for IVM were implanted into female BALB/c mice. The murine colon cancer cell line CT26HA was inoculated in the skin within the chamber. Fluorescein isothiocyanate dextran (FITC-dex) was injected IV to enhance vessel observation prior to nicardipine (8 μg/mouse). Observations were performed at 100x magnification using a modified Olympus microscope for 10 minutes. Naive mice were used for control observations. Mice bearing CT26HA were observed on post-inoculation day 5, 12 and 20. Vessel architecture and vessel diameter in response to nicardipine were compared. Results In non-CT26HA bearing mice, nicardipine resulted in a greater than 10% increase in skin vessel diameters directly measured using IVM (pre-nicardipine diameter 82.4 ± 3.6 μm versus post-nicardipine diameter 93.0 ± 3.9 μm. In CT26HA bearing mice, abnormal vessels were observed as early as day 7 even in the absence of a solid tumor mass. Vessel abnormalities included haphazard areas of increased vessel density, aberrant vessel branching patterns, nonfunctional vessels, and altered flow rates. Following nicardipine injection, the diameter of larger tumor-associated vessels did not increase and remained constant (pre: 111.2 ± 2.7 μm vs post: 109.1 ± 3.3 μm). Paradoxically, for smaller vessels ( Conclusions Observation of dynamic vessel changes from vasoactive agents is feasible using IVM. For tumor-associated vessels, nicardipine was not shown to increase vessel diameter and counterintuitively decreased diameters of smaller vessels. Implication on drug delivery from vasoactive agents will lead to further pre-clinical study of applications for human IVM. Citation Format: Emmanuel M. Gabriel, Daniel Fisher, Minhyung Kim, Colin Powers, Anthony Visioni, Jason Muhitch, Joseph Skitzki. Dynamic control of tumor vasculature with direct observation using intravital microscopy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4225.