Keane Simon, Martinsson Tommy, Kogner Per, Ejeskär Katarina
Translational Medicine, School of Health Sciences, University of Skövde, Skövde, Sweden.
Department of Laboratory Medicine, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
Cancer Cell Int. 2021 Mar 16;21(1):170. doi: 10.1186/s12935-021-01851-w.
Neuroblastoma is a childhood neural crest tumor showing large clinical and genetic heterogeneity, one form displaying 11q-deletion is very aggressive. It has been shown that 11q-deletion results in decreased expression of DLG2, a gene residing in the deleted region. DLG2 has a number of different isoforms with the main difference is the presence or absence of a L27 domain. The L27 domain containing DLG proteins can form complexes with CASK/MPP and LIN7 protein family members, which will control cell polarity and signaling.
We evaluated the DLG gene family and the LIN7 gene family for their expression in differently INSS staged neuroblastoma from publically available data and primary tumors, we included two distinct DLG1 and DLG2 N-terminal transcript isoforms encoding L27 domains for their expression. Functionality of DLG2 isoforms and of LIN7A were evaluated in the 11q-deleted neuroblastoma cell line SKNAS.
In neuroblastoma only two DLG2 isoforms were expressed: isoform 2 and isoform 7/8. Using the array data we could determine that higher expression of DLG members that contain L27 domains correlated to better survival and prognosis. Whilst DLG1 showed a decrease in both isoforms with increased INSS stage, only the full length L27 containing DLG2 transcripts DLG2-isoform 7/8 showed a decrease in expression in high stage neuroblastoma. We could show that the protein encoded by DLG2-isoform 7 could bind to LIN7A, and increased DLG2-isoform 7 gene expression increased the expression of LIN7A, this reduced neuroblastoma cell proliferation and viability, with increased BAX/BCL2 ratio indicating increased apoptosis.
We have provided evidence that gene expression of the L27 domain containing DLG2-isoform 7/8 but not L27 domain lacking DLG2-isoform 2 is disrupted in neuroblastoma, in particular in the aggressive subsets of tumors. The presence of the complete L27 domain allows for the binding to LIN7A, which will control cell polarity and signaling, thus affecting cancer cell viability.
神经母细胞瘤是一种儿童期神经嵴肿瘤，具有很大的临床和遗传异质性，其中一种表现为11q缺失的形式极具侵袭性。研究表明，11q缺失导致位于缺失区域的DLG2基因表达降低。DLG2有多种不同的异构体，主要区别在于是否存在L27结构域。含有L27结构域的DLG蛋白可与CASK/MPP和LIN7蛋白家族成员形成复合物，从而控制细胞极性和信号传导。
我们从公开数据和原发性肿瘤中评估了DLG基因家族和LIN7基因家族在不同国际神经母细胞瘤分期系统（INSS）分期的神经母细胞瘤中的表达情况，我们纳入了两种不同的编码L27结构域的DLG1和DLG2 N端转录异构体的表达情况。在11q缺失的神经母细胞瘤细胞系SKNAS中评估了DLG2异构体和LIN7A的功能。
在神经母细胞瘤中仅表达两种DLG2异构体：异构体2和异构体7/8。利用阵列数据我们可以确定，含有L27结构域的DLG成员的高表达与更好的生存率和预后相关。虽然随着INSS分期增加，DLG1的两种异构体表达均降低，但只有包含全长L27的DLG2转录本DLG2-异构体7/8在晚期神经母细胞瘤中表达降低。我们可以证明，DLG2-异构体7编码的蛋白可与LIN7A结合，增加DLG2-异构体7基因表达可增加LIN7A的表达，这会降低神经母细胞瘤细胞的增殖和活力，同时BAX/BCL2比值增加表明细胞凋亡增加。
我们提供的证据表明，在神经母细胞瘤中，尤其是在侵袭性肿瘤亚组中，含有L27结构域的DLG2-异构体7/8的基因表达受到破坏，而缺乏L27结构域的DLG2-异构体2则未受影响。完整L27结构域的存在允许与LIN7A结合，从而控制细胞极性和信号传导，进而影响癌细胞的活力。
