B and T-Cell Lymphoma Patient-Derived Xenografts Recapitulate Aspects of Disease Biology and Progression and Represent Novel Tools for Preclinical Drug Development

Lymphomas represent nearly 70 distinct diseases with unique clinical presentations, therapeutic responses and underlying biology.  There is a pressing shortage of publically available cell line and in vivo models of nearly all of these diseases, which has severely hampered efforts to understand and target their biology.  To address this issue, we have established a repository of patient-derived xenografts (PDX) of lymphomas by engrafting human tumors into immunodeficient NOD/SCID/IL2rg^null (NSG) mice.  These lymphomas, along with a spectrum of other PDXs of hematologic malignancies, are available to collaborators through the online portal PRoXe (Public Repository of Xenografts) at http://PRoXe.org. Blood and bone marrow specimens involved with tumor are injected by tail vein (IV) injection.  Lymph node and extranodal biopsy specimens are implanted under the renal capsule as a 1x1x2mm tumor seed (renal), which maintains the in situ microarchitecture.  A full description of xenografted lymphomas is included in the Table.

Disease	Type of implant	# in 1st passage	# in 2nd passage or higher
T-cell prolymphocytic leukemia	IV	1
Angioimmunoblastic T-cell lymphoma	IV	1	1
Mantle cell lymphoma	IV	1	2
Double-hit DLBCL	IV		2
Sézary Syndrome	IV		1
Adult T-cell Leukemia/Lymphoma	IV		1
Diffuse large B cell lymphoma	IV		2
Diffuse large B cell lymphoma	renal		2
Marginal zone lymphoma	renal	1	1
NK/T-cell lymphoma	renal		1
Peripheral T-cell lymphoma-NOS	renal	1
Breast implant-associated anaplastic large cell lymphoma	renal	1

Engrafted PDXs have been extensively characterized by immunohistochemistry, flow cytometry, transcriptome sequencing and targeted DNA sequencing.  Flow cytometric analysis of patient tumors and their respective xenografts consistently revealed highly concordant immunophenotypes compared to the original tumors.  Similarly, immunohistochemistry of involved tissues confirmed retention of tumor immunophenotypes, architecture, and even tissue tropism in the PDXs.  Examples include a Sézary syndrome PDX that was injected by tail vein and trafficked to spleen, bone marrow, blood and skin, a diffuse large B-cell lymphoma (DLBCL) PDX that infiltrated the CNS, and a second DLBCL PDX that was implanted into the renal capsule of the left kidney and progressed within 8 weeks to bilateral renal involvement.  Other notable models include a breast implant-associated, ALK-negative anaplastic large cell lymphoma implanted under the renal capsule that metastasized to the liver and spleen while uniformly retaining CD30 positivity. Two double-hit lymphoma (DHL) PDXs maintained their CD20-negative phenotype through serial passage to P1. A peripheral T-cell lymphoma-NOS (PTCL) specimen implanted under the renal capsule engrafted in the spleen, with a notable admixture of nonmalignant T cells and scattered EBV-positive B cells. T-cell receptor gene rearrangement PCR performed on this PTCL demonstrated an identical rearrangement pattern in the primary tumor and the PDX.  Luciferized mantle cell lymphoma and DHL PDXs clearly home to bone marrow, lymph nodes, spleen, and liver as early as two weeks after injection. These findings support the utility of these PDX lines as in vivo models that more accurately recapitulate the human disease than commonly used subcutaneous cell line models. In addition to generating PDXs that remain faithful to their source tumors, we have witnessed interesting examples of in vivo histologic transformation, opening the door to studies of disease progression. One primary follicular lymphoma specimen injected into a cohort of mice transformed to DLBCL in one mouse and a lymphoblastic lymphoma-like disease in another mouse, as confirmed by IHC and flow cytometry.  Further xenografting of primary tumors is underway with the goal of establishing a large repository of lymphoma PDXs useful for biologic interrogation and preclinical trials.