Novel Protocol for Generating Physiologic Immunogenic Dendritic Cells

Abstract

Extracorporeal photochemotherapy (ECP) is a widely used cancer immunotherapy for cutaneous T cell lymphoma (CTCL), operative in over 350 university centers worldwide. While ECP's clinical efficacy and exemplary safety profile have driven its widespread use, elucidation of the underlying mechanisms has remained a challenge, partly owing to lack of a laboratory ECP model. To overcome this obstacle and create a simple, user-friendly platform for ECP research, we developed a scaled-down version of the clinical ECP leukocyte-processing device, suitable for work with both mouse models, and small human blood samples. This device is termed the Transimmunization (TI) chamber, or plate. In a series of landmark experiments, the miniaturized device was used to produce a cellular vaccine that regularly initiated therapeutic anticancer immunity in several syngeneic mouse tumor models. By removing individual factors from the experimental system and ascertaining their contribution to the in vivo anti-tumor response, we then elucidated key mechanistic drivers of ECP immunizing potential. Collectively, our results revealed that anti-tumor effects of ECP are initiated by dendritic cells (DC), physiologically generated through blood monocyte interaction with platelets in the TI plate, and loaded with antigens from tumor cells whose apoptotic cell death is finely titrated by exposure to the photoactivatable DNA cross-linking agent 8-methoxypsoralen and UVA light (8-MOP A ). When returned to the mouse, this cellular vaccine leads to specific and transferable anti-tumor T cell immunity. We verified that the TI chamber is also suitable for human blood processing, producing human DCs fully comparable in activation state and profile to those derived from the clinical ECP chamber. The protocols presented here are intended for ECP studies in mouse and man, controlled generation of apoptotic tumor cells with 8-MOP A , and rapid production of physiologic human and mouse monocyte-derived DCs for a variety of applications.

Mycosis fungoides and Sézary syndrome

“…Interferon can also be successfully combined with other skin-directed therapies, such as PUVA, bexarotene, and extracorporeal photopheresis (ECP) [ 86 ], a type of phototherapy in which psoralen exposure precedes extracorporeal circulation. Psoralen binds to DNA after UVA radiation and leads to apoptosis of lymphocytes as well as an enhanced host immune response induced by monocyte activation and dendritic cell differentiation [ 87 , 88 ]. Following a landmark report of a response in 73% of patients, ECP has become a first line treatment for advanced-stage MF and SS [ 89 ].…”

Cutaneous T‐cell lymphomas: 2023 update on diagnosis, risk‐stratification, and management

“… 215 Although the precise mechanism of action is incompletely understood, evidence suggests that ECP has immunomodulatory effects which may augment host anti‐tumor immunity. 216 , 217 It is not surprising then that the median time to response following the initiation of ECP is approximately 6 months. Median survival exceeding 8 years has been observed in ECP treated patients and among complete responders, many experience durable responses which may permit, for some, weaning from CTCL‐directed therapies.…”