Dual blockade of the PI3K/Akt/mTOR pathway inhibits posttransplant Epstein-Barr virus B cell lymphomas and promotes allograft survival

Abstract

Abbreviations: 4EBP, 4E-binding protein; DMSO, dimethyl sulfoxide; EBV, Epstein-Barr virus; ERK, extracellular signal-regulated kinase; IC 50 , half maximal Inhibitory concentration; LI, Loewe index; LMP1, latent membrane protein 1; MAPK, mitogen-activated protein kinase; mTORC, mammalian target of rapamycin complex; mTOR, mammalian target of rapamycin; NOD-SCID, Non-obese diabetic/severe combined immunodeficiency; PI3K, Phospho-inositide 3-kinase; PTLD, posttransplant lymphoproliferative disorder; RI, reduction of immunosuppression; SEM, standard error of the mean; STAT, signal transducer and activator of transcription. Posttransplant lymphoproliferative disorder (PTLD) is a serious complication of organ transplantation that often manifests as Epstein-Barr virus (EBV)-associated B cell lymphomas. Current treatments for PTLD have limited efficacy and can be associated with graft rejection or systemic toxicities. The mTOR inhibitor, rapamycin, suppresses tumor growth of EBV+ B cell lymphoma cells in vitro and in vivo; however, the efficacy is limited and clinical benefits of mTOR inhibitors for PTLD are variable. Here, we show constitutive activation of multiple nodes within the PI3K/Akt/mTOR pathway in EBV+ PTLD-derived cell lines. Inhibition of either PI3K or Akt, with specific inhibitors CAL-101 and MK-2206, respectively, diminished growth of EBV+ B cell lines from PTLD patients in a dose-dependent manner. Importantly, rapamycin combined with CAL-101 or MK-2206 had a synergistic effect in suppressing cell growth as determined by IC 50 isobolographic analysis and Loewe indices. Moreover, these combinations were significantly more effective than rapamycin alone in inhibiting tumor xenograft growth in NOD-SCID mice. Finally, both CAL-101 and MK-2206 also prolonged survival of heterotopic cardiac allografts in C57BL/6 mice. Thus, combination therapy with rapamycin and a PI3K inhibitor, or an Akt inhibitor, can be an efficacious treatment for EBV-associated PTLD, while simultaneously promoting allograft survival. K E Y W O R D S basic (laboratory) research/science, immunosuppressant-mechanistic target of rapamycin (mTOR), immunosuppression/immune modulation, infection and infectious agents-viral: Epstein-Barr Virus (EBV), infectious disease, posttransplant lymphoproliferative disorder (PTLD)

Epstein-Barr Virus Latent Membrane Protein 1 Regulates Host B Cell MicroRNA-155 and Its Target FOXO3a via PI3K p110α Activation

“…In preclinical models, we have previously demonstrated that PI3K pathway inhibition is a rational therapeutic target for EBV+ PTLD (Furukawa et al, 2013;Hatton et al, 2013;Sang et al, 2019); our data here suggest that one mechanism by which this works is by reducing miR-155 expression. miR-155 inhibitors, such as MRG-106 (miRagen Therapeutics Inc.), are currently in phase I clinical trials for cutaneous T cell lymphoma, chronic lymphocytic leukemia, diffuse large B cell lymphoma, and adult T cell leukemia/lymphoma (ClinicalTrials.gov Identifier NCT02580552).…”

Signaling pathways of EBV-induced oncogenesis

“…Many studies have shown that PI3K/AKT signaling pathway plays an important role in PTLD infected by EBV. In the study of Sang et al [ 33 ], several nodes inside the PI3K/AKT/mTOR signaling pathway of EBV-positive PTLD-derived cell lines were activated. Both CAL-101 and MK-2206, specific inhibitors of PI3K/AKT, can extend the survival time of C57BL/6 mice that received a cardiac allograft and, when combined with rapamycin, can inhibit cancer cell growth.…”

Posttransplant Lymphoproliferative Disorder Following Kidney Transplantation: A Review

“…Although their use in PTLD has been very limited, there seems to be a strong in vitro rationale in PTLD as well. 65,66 In addition, some of these molecules, including the Bruton tyrosine kinase inhibitor ibrutinib, may also be effective in graft rejection.…”