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Rapamycin Attenuates BAFF-extended Proliferation and Survival via Disruption of mTORC1/2 Signaling in Normal and Neoplastic B-lymphoid Cells

Rapamycin Attenuates BAFF-extended Proliferation and Survival via Disruption of mTORC1/2 Signaling in Normal and Neoplastic B-lymphoid Cells

Qingyu Zeng, Shanshan Qin, Hai Zhang, Beibei Liu, Jiamin Qin, Xiaoxue Wang, Ruijie Zhang, Chunxiao Liu, Xiaoqing Dong, Shuangquan Zhang, Shile Huang, Long Chen

J Cell Physiol. 2018 Jan;233(1):516-529.

PMID: 28300280

Abstract:

B cell activating factor from the TNF family (BAFF) stimulates B-cell proliferation and survival, but excessive BAFF promotes the development of aggressive B cells leading to malignant and autoimmune diseases. Recently, we have reported that rapamycin, a macrocyclic lactone, attenuates human soluble BAFF (hsBAFF)-stimulated B-cell proliferation/survival by suppressing mTOR-mediated PP2A-Erk1/2 signaling pathway. Here, we show that the inhibitory effect of rapamycin on hsBAFF-promoted B cell proliferation/survival is also related to blocking hsBAFF-stimulated phosphorylation of Akt, S6K1, and 4E-BP1, as well as expression of survivin in normal and B-lymphoid (Raji and Daudi) cells. It appeared that both mTORC1 and mTORC2 were involved in the inhibitory activity of rapamycin, as silencing raptor or rictor enhanced rapamycin's suppression of hsBAFF-induced survivin expression and proliferation/viability in B cells. Also, PP242, an mTORC1/2 kinase inhibitor, repressed survivin expression, and cell proliferation/viability more potently than rapamycin (mTORC1 inhibitor) in B cells in response to hsBAFF. Of interest, ectopic expression of constitutively active Akt (myr-Akt) or constitutively active S6K1 (S6K1-ca), or downregulation of 4E-BP1 conferred resistance to rapamycin's attenuation of hsBAFF-induced survivin expression and B-cell proliferation/viability, whereas overexpression of dominant negative Akt (dn-Akt) or constitutively hypophosphorylated 4E-BP1 (4EBP1-5A), or downregulation of S6K1, or co-treatment with Akt inhibitor potentiated the inhibitory effects of rapamycin. The findings indicate that rapamycin attenuates excessive hsBAFF-induced cell proliferation/survival via blocking mTORC1/2 signaling in normal and neoplastic B-lymphoid cells. Our data underscore that rapamycin may be a potential agent for preventing excessive BAFF-evoked aggressive B-cell malignancies and autoimmune diseases.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
IAR4246396	4EBP1 Active human			Price

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