Direct and immune-mediated cytotoxicity of interleukin-21 contributes to antitumor effects in mantle cell lymphoma

Abstract

• IL-21 activates IL-21R-dependent singling to mediate direct cytotoxicity of MCL cells.• Indirect effects of IL-21 on immune effector cells also contribute to antitumor effects against MCL.Mantle cell lymphoma (MCL) is a distinct subtype of non-Hodgkin lymphoma characterized by overexpression of cyclin D1 in 95% of patients. MCL patients experience frequent relapses resulting in median survival of 3 to 5 years, requiring more efficient therapeutic regimens. Interleukin (IL)-21, a member of the IL-2 cytokine family, possesses potent antitumor activity against a variety of cancers not expressing the IL-21 receptor (IL-21R) through immune activation. Previously, we established that IL-21 exerts direct cytotoxicity on IL-21R-expressing diffuse large B-cell lymphoma cells. Herein, we demonstrate that IL-21 possesses potent cytotoxicity against MCL cell lines and primary tumors. We identify that IL-21-induced direct cytotoxicity is mediated through signal transducer and activator of transcription 3-dependent cMyc upregulation, resulting in activation of Bax and inhibition of Bcl-2 and Bcl-X L . IL-21-mediated cMyc upregulation is only observed in IL-21-sensitive cells. Further, we demonstrate that IL-21 leads to natural killer (NK)-cell-dependent lysis of MCL cell lines that were resistant to direct cytotoxicity. In vivo treatment with IL-21 results in complete FC-muMCL1 tumor regression in syngeneic mice via NK-and T-cell-dependent mechanisms. Together, these data indicate that IL-21 has potent antitumor activity against MCL cells via direct cytotoxic and indirect, immune-mediated effects. (Blood. 2015;126(13):1555-1564

Anti-CD20-interleukin-21 fusokine targets malignant B cells via direct apoptosis and NK-cell–dependent cytotoxicity

“…To further evaluate the potential contribution of STAT-3, BAX, and cMyc to fusokine-induced cell death, we performed knockdown of these proteins using specific siRNAs. As previously reported, 32,35 inhibition of STAT-3 completely abrogated IL-21-induced cell death. Although fusokine treatment led to more pronounced death than IL-21, STAT-3 inhibition still completely blocked fusokine-induced cell death, as opposed to control siRNA ( Figure 3C).…”

“…[26][27][28][29][30][31] We and others recently showed that IL-21 enhances rituximab-mediated ADCC of NHL cells, including mantle cell lymphoma (MCL) and chronic lymphocytic leukemias. 20,32,33 Similarly, increased ADCC was also observed in a murine breast cancer model treated with the anti-HER2 Ab (trastuzumab) and IL-21. 21,34 Apart from its immunostimulatory effects, IL-21 exerts direct cytotoxicity on a variety of IL-21R-expressing NHLs, including diffuse large B-cell lymphoma (DLBCL), MCL, chronic lymphocytic leukemia, and follicular lymphoma.…”

“…21,34 Apart from its immunostimulatory effects, IL-21 exerts direct cytotoxicity on a variety of IL-21R-expressing NHLs, including diffuse large B-cell lymphoma (DLBCL), MCL, chronic lymphocytic leukemia, and follicular lymphoma. 32,[35][36][37][38][39][40][41][42] We found that the direct apoptotic effects of IL-21 in DLBCL and MCL were mediated via activation of an IL-21R-dependent signaling pathway that leads to phosphorylation of STATs followed by upregulation of cMyc and Bax and downregulation of BCL-2 and BCL-XL. 32,35 These studies suggest IL-21 may become a potent adjuvant to cancer immunotherapy against B-cell lymphoma.…”

“…32,[35][36][37][38][39][40][41][42] We found that the direct apoptotic effects of IL-21 in DLBCL and MCL were mediated via activation of an IL-21R-dependent signaling pathway that leads to phosphorylation of STATs followed by upregulation of cMyc and Bax and downregulation of BCL-2 and BCL-XL. 32,35 These studies suggest IL-21 may become a potent adjuvant to cancer immunotherapy against B-cell lymphoma. 37 Indeed, a recent clinical trial of IL-21 in combination with rituximab for relapsed or refractory low-grade B-cell lymphomas showed clinical responses in 8 (42%) of 19 patients, with a response rate of 33% in rituximab-resistant patients.…”

“…We have previously demonstrated that IL-21-induced apoptosis is dependent on STAT3, cMYC, and Bax, and is independent of STAT1 in DLBCL and MCL cell lines. 32,35 Treatment with aCD20-IL-21 fusokine resulted in upregulation of pSTAT1, pSTAT3, and pSTAT5, similar to IL-21 alone, and was not observed in cells treated with the parent aCD20-IgG1 Ab ( Figure 3A). Furthermore, we also found upregulation in cMyc, BAX, and downregulation of the antiapoptotic proteins BCL-xL and Bcl-2, which was more pronounced in the fusokine-treated cells compared with native IL-21 ( Figure 3B; supplemental Figure 4A).…”