Convergence of Acquired Mutations and Alternative Splicing of CD19 Enables Resistance to CART-19 Immunotherapy.
Convergence of Acquired Mutations and Alternative Splicing of CD19 Enables Resistance to CART-19 Immunotherapy.
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DOI：
10.1158/2159-8290.cd-15-1020
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发表时间：
2015-12
期刊：
影响因子：
28.2
通讯作者：
Thomas-Tikhonenko A
中科院分区：
文献类型：
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作者：
Sotillo E;Barrett DM;Black KL;Bagashev A;Oldridge D;Wu G;Sussman R;Lanauze C;Ruella M;Gazzara MR;Martinez NM;Harrington CT;Chung EY;Perazzelli J;Hofmann TJ;Maude SL;Raman P;Barrera A;Gill S;Lacey SF;Melenhorst JJ;Allman D;Jacoby E;Fry T;Mackall C;Barash Y;Lynch KW;Maris JM;Grupp SA;Thomas-Tikhonenko A
CD19抗原在大多数b细胞急性淋巴细胞白血病（B-ALL）上表达，可以用嵌合抗原受体- armed T细胞（CART-19）靶向，但10%至20%的儿科应答者会发生复发并丢失表位。我们在一些复发样本中检测到跨越CD19位点的半合子缺失和CD19外显子2的新移码和错义突变。然而，我们也发现了CD19 mRNA的选择性剪接，包括一个缺乏外显子2的物种。Pull-down/siRNA实验发现SRSF3是参与外显子2保留的剪接因子，其水平在复发的B-ALL中较低。通过基因组编辑，我们证明了外显子2跳过B-ALL细胞中的外显子2突变，并允许表达n端截断的CD19变体，该变体无法触发CART-19的杀伤，但部分挽救了与CD19丢失相关的缺陷。因此，这种抗性机制是基于有害突变和随后的选择性剪接RNA异构体选择的组合。在B-ALL患者中，CART-19的有效率为70%，但也会产生逃逸变体。我们发现潜在的机制是选择预先存在的具有受损的CART-19表位的CD19异构体。这一机制提示了靶向CD19外结构域的可能性，这可能提高b细胞肿瘤患者的生存率。
The CD19 antigen, expressed on most B-cell acute lymphoblastic leukemias (B-ALL), can be targeted with chimeric antigen receptor–armed T cells (CART-19), but relapses with epitope loss occur in 10% to 20% of pediatric responders. We detected hemizygous deletions spanning the CD19 locus and de novo frameshift and missense mutations in exon 2 of CD19 in some relapse samples. However, we also discovered alternatively spliced CD19 mRNA species, including one lacking exon 2. Pull-down/siRNA experiments identified SRSF3 as a splicing factor involved in exon 2 retention, and its levels were lower in relapsed B-ALL. Using genome editing, we demonstrated that exon 2 skipping bypasses exon 2 mutations in B-ALL cells and allows expression of the N-terminally truncated CD19 variant, which fails to trigger killing by CART-19 but partly rescues defects associated with CD19 loss. Thus, this mechanism of resistance is based on a combination of deleterious mutations and ensuing selection for alternatively spliced RNA isoforms. CART-19 yield 70% response rates in patients with B-ALL, but also produce escape variants. We discovered that the underlying mechanism is the selection for preexisting alternatively spliced CD19 isoforms with the compromised CART-19 epitope. This mechanism suggests a possibility of targeting alternative CD19 ectodomains, which could improve survival of patients with B-cell neoplasms.