We performed gene expression profiling of mRNA/cDNA isolated from N = 117 flow sorted CLL. We detected aberrant expression of the metabolic enzyme branched chain amino acid transferase (BCAT1) in CLL with del17p/TP53mut. Through extensive validation, we confirmed the highly preferential expression of BCAT1 in CLL with del17p/TP53mut (66%) or trisomy 12 (77%). BCAT1 was not expressed in B cells isolated from normal human lymph nodes. The products of the bidirectional BCAT1 reaction, including leucine, acetyl-CoA, and alpha-ketoglutarate are known activators of MTOR. We measured an ~two-fold higher MTOR activity via normalized p-S6K levels in primary CLL with BCAT1 high versus absent expression before and after sIgM crosslinking. Through steady state metabolomics and heavy isotope metabolic tracing in primary CLL cells, we demonstrate that CLL cells are avid consumers of branched chain amino acids (BCAAs) and that BCAT1 in CLL engages in bidirectional substrate reactions. Of additional interest, CLL with aberrant BCAT1 expression were less sensitive to Venetoclax-induced apoptosis. Biologically, three CLL-derived cell lines with disruption of BCAT1 had substantially reduced growth ex vivo. Clinically, the expression of any detectable BCAT1 protein in CLL independently associated with shorter median survival (125 months versus 296 months; p < 0.0001), even after exclusion of del17p/TP53mut cases.

我们对从 N = 117 流式分选 CLL 中分离的 mRNA/cDNA 进行了基因表达谱分析。我们在具有 del17p/TP53突变的 CLL 中检测到代谢酶支链氨基酸转移酶 （BCAT1） 的异常表达。通过广泛的验证，我们证实了 BCAT1 在 CLL 中高度优先表达，具有 del17p/TP53突变 （66%） 或 12 三体 （77%）。BCAT1 在从正常人淋巴结分离的 B 细胞中不表达。双向 BCAT1 反应的产物，包括亮氨酸、乙酰辅酶 A 和 α-酮戊二酸，是已知的 MTOR 激活剂。我们通过在 BCAT1 高表达的原发性 CLL 中标准化的 p-S6K 水平测量了 sIgM 交联前后与不存在表达相比，MTOR 活性高出 ~2 倍。通过原代 CLL 细胞中的稳态代谢组学和重同位素代谢示踪，我们证明 CLL 细胞是支链氨基酸 （BCAA） 的狂热消费者，并且 CLL 中的 BCAT1 参与双向底物反应。其他有趣的是，BCAT1 表达异常的 CLL 对 Venetoclax 诱导的细胞凋亡不太敏感。在生物学上，三种破坏 BCAT1 的 CLL 衍生细胞系在体外显著减少了生长。临床上，CLL 中任何可检测到的 BCAT1 蛋白的表达与较短的中位生存期独立相关（125 个月对 296 个月;p < 0.0001），即使在排除 del17p/TP53突变情况后也是如此。