Background
Splicing isoforms of Bcl-x
Regulation of Bcl-x pre-mRNA splicing
Cis-regulatory elements
Trans-acting factors
Regulation methods | Mechanism | Selection | Ref | |
---|---|---|---|---|
RNA binding proteins | Sam68 | Recruit hnRNP A1 to certain regions. | Bcl-xS | [26] |
SRSF1 (ASF/SF2) | Compete with hnRNP A1. | Bcl-xL | ||
SRSF10 | Collaborate with hnRNP A1/A2 and Sam68. | Bcl-xS | [29] | |
SRSF2 (SC35) | As a direct transcriptional target of E2F1. | Bcl-xS | [30] | |
SRSF3 | Favor the selection of the 5' DSS. | Bcl-xS | [28] | |
SRSF7 | Favor the selection of the 5' DSS. | Bcl-xL | [28] | |
SRSF9 (SRp30c) | Bind to ML2 and AM2. | Bcl-xL | [21] | |
TRA2β | Favored selection of the 5' DSS. | Bcl-xS | [28] | |
hnRNP F/H | Bind to B2G region. | Bcl-xS | ||
PTBP1 (hnRNP I) | Bind to polypyrimidine to promote 5' DSS selection | Bcl-xS | [28] | |
hnRNP A1 | Interact with Sam68. | Bcl-xS | ||
hnRNP A2/B1 | Regulated by Fyn activity. | Bcl-xL | [37] | |
hnRNP K | Bind to silencer element of the 5' DSS. | Bcl-xL | [20] | |
RBM4 | Antagonize oncogenic SRSF1. | Bcl-xS | [38] | |
RBM10 (S1-1) | Block the GGGUAAG of exon 2. | Bcl-xS | [39] | |
RBM11 | Antagonize SRSF1. | Bcl-xS | [40] | |
RBM25 | Bind to CGGGCA sequence within exon 2. | Bcl-xS | [41] | |
Transcription factors | E2F1 | Upregulate SC35 protein expression. | Bcl-xS | [30] |
FBI-1 | Interact with Sam68 and affects its binding. | Bcl-xL | [31] | |
TCERG1 | Increase the elongation rate of RNAPII. | Bcl-xS | [32] | |
FOXP3 | Repress hnRNPF binding to 5'DSS. | Bcl-xL | [33] | |
SAP155 (SF3B1) | Bind to CRCE 1 region. | Bcl-xL | [42] | |
Signal pathway | PKC signal | Through SB1 to repress the 5'DSS splicing. | Bcl-xL | [43] |
PI3K/PKCι signal | Regulate SAP155-CRCE1 complex formation. | Bcl-xL | [44] | |
LPS/PRMT2 or TNF-α pathway | Interact with Sam68 and regulate its subcellular localization via its SH3 domain. | Bcl-xL | [45] | |
G4s and G4s ligands | G-quadruplexes (G4s) | Close to the two alternative 5'SS to compete with other RNA structures or proteins | Bcl-xS or Bcl-xL | |
G-quadruplex ligands (GQC05) | Stabilize G-quadruplexes. | Bcl-xS | [46] | |
EJC | Exon junction complex ( EJC ) | RNPS1 and core EJC proteins control Bcl-x splicing through cis-acting elements SB1. | Bcl-xL | [48] |
Epigenetic modifications
The function of aberrant Bcl-x splicing in cancer
Apoptosis
Cancer type | Bcl-xL/S | Function | Ref | |
---|---|---|---|---|
Apoptosis | Hepatocellular Carcinomas | Bcl-xL↑ | Inhibit apoptosis initiated by cellular stimuli | [65] |
Colorectal cancer (CRC) | Bcl-xL↑ | Drive tumourigenesis and progression. | [66] | |
Breast cancer | Bcl-xL↑ | Suppress BETi-induced apoptosis. | [67] | |
Meningioma | Bcl-xL↑ | Contribute to apoptosis induced by Dovitinib. | [68] | |
Malignancy | Gastric cancer | Bcl-xL↑ | Associated with high Beclin1 expression. | [69] |
Tongue Carcinoma | Bcl-xL↑ | Related to the degree of differentiation. | [70] | |
Hodgkin lymphoma | Bcl-xL↑ | Consistent with the severity of patients. | [71] | |
Myeloproliferative neoplasms | Bcl-xL↑ | Progressively over-expressed. | [72] | |
Lymphomas | Bcl-XS/L↓ | Expressed by malignant cells. | [73] | |
Wilms' tumours | Bcl-XS/L↓ | Negatively correlated with tumour stage. | [74] | |
Endometrial carcinoma | Bcl-XS/L↓ | Correlated with pathological grading. | [75] | |
Metastasis | Pancreatic cancer | Bcl-xL↑ | Promote metastasis | [76] |
Glioblastoma | Bcl-xL↑ | Promote cell migration, invasion, angiogenesis and stemness. | [77] | |
Melanoma | Bcl-xL↑ | [77] | ||
Drug-resistance | Chondrosarcoma | Bcl-xL↑ | Confer resistance to chemotherapy. | [78] |
Ewing sarcoma | Bcl-xL↑ | Resistant to olaparib. | [79] | |
Ovarian carcinoma (OC) | Bcl-xL↑ | Confer resistance to chemotherapy. | [80] | |
Hepatocellular carcinoma | Bcl-xL↑ | Chemoresistance and poor prognosis. | [81] | |
Urothelial Carcinoma | Bcl-xL↑ | Effectively inhibited cisplatin-resistant UCs. | [82] | |
Radiation | laryngeal cancer | Bcl-xL↑ | Associated with radioresistant. | [83] |
Non-small cell lung cancer | Bcl-xL↑ | Enhance irradiation resistance. | [84] | |
Prostate cancer | Bcl-xL↑ | Enhance survival to cells exposured to IR. | [85] | |
Osteosarcoma | Bcl-xL↑ | Enhance irradiation resistance. | [86] | |
Malignant pleural mesothelioma | Bcl-xL↑ | Negatively associated with radiosensitivity. | [87] |
Autophagy
Invasion and metastasis
Anti-tumor immunity
Clinical impaction of Bcl-x splicing in cancer
Chemotherapy
Radiotherapy
Strategies modulating Bcl-x splicing in cancer
Splice-switching oligonucleotides
Cells types | Sequence | Length | Chemistry | Ref |
---|---|---|---|---|
K562 | 5'-GCTTGGTTCTTACCCAGCCGCCGTT-3' | 25 mer | vMO | [5] |
Primary HSCs | 5'-TGGTTCTTACCCAGCCGCCG-3' | 20 mer | 2'-OMe-PS | [97] |
U87, U251 | 5'-TGGTTCTTACCCAGCCGCCG-3' | 20 mer | 2'-MOE-PS | [142] |
B16F10 | 5'-TGGTTCTTACCCAGCCGCCG-3' | 20 mer | 2'-MOE-PS | [143] |
Human RPE | 5'-TGGTTCTTACCCAGCCGCCG-3' | 20 mer | 2'-MOE | [144] |
A549 | 5'-CTGGATCCAAGGCTCTAGGT-3' | 20 mer | 2'-MOE | [145] |
PC-3 | 5'-ACCCAGCCGCCGUUCUCC-3' | 18 mer | 2'-OMe-PS | [146] |
MCF-7 | 5'-ACCCAGCCGCCGUUCUCC-3' | 18 mer | 2'-OMe-PS | [146] |
Hela | 5'-ACCCAGCCGCCGUUCUCC-3' | 18 mer | 2'-OMe-PS | [146] |
Small molecular modulators redirect Bcl-x splicing
BH3 mimetics inhibit Bcl-xL isoform
Multiple targets | Compounds | Origin | Stage | Ref |
---|---|---|---|---|
Bcl-xL | A-1155463 | Structure-based design. | Preclinical | [159] |
A-1331852 | Structure-based design. | Preclinical | [160] | |
WEHI-539 | Structure- based design | Preclinical | [161] | |
DT2216 | Proteolysis targeting chimera | Preclinical | [162] | |
XZ424 | Proteolysis targeting chimera | Preclinical | [163] | |
ABBV-155 | Structure-based design | Phase I | NCT03595059 | |
Bcl-xL Bcl-2 | AZD4320 | Structure-based design | Preclinical | [164] |
BM-957 | Structure-based design | Preclinical | [165] | |
BM-1197 | Structure-based design | Preclinical | [166] | |
S44563 | Structure-based design | Preclinical | [167] | |
APG-1252 | Structure-based design | Phase I/II | [168] | |
Bcl-xL Bcl-2 Bcl-w | Ch282-5 | Gossypol derivative | Preclinical | [169] |
ABT-737 | Synthetic, acylsulfonamide-based | Phase I/II | [170] | |
ABT-263 (Navitoclax) | Derivant of ABT-737 | Phase I/II/III | [171] | |
Bcl-xL, Bcl-2, Mcl-1 | BH3-M6 | Synthetic terphenyl scaffold | Preclinical | [172] |
Bcl-xL, Bcl-2, Bcl-w, Mcl-1 | TW-37 | Benzenesulfonyl derivative of gossypol | Preclinical | [173] |
BI-97C1 (Sabutoclax) | Diastereoisomer of Apogossypol | Preclinical | [174] | |
BIM-SAHB | Stapled Bim peptide | Preclinical | [175] | |
GX15-070 (Obatoclax) | Synthetic indolyl-dipyrromethene | Phase I/II/III | [176] | |
AT-101 | (−)-gossypol enantiomer | Phase I/II/III | [177] | |
Bcl-2 | S55746 | Structure-based design | Phase I | [178] |
ABT-199 (Venetoclax) | Derivant of ABT-263 | Phase I/II/III | [127] | |
Mcl-1 | A-1210477 | Structure-based design | Preclinical | [179] |
UMI-77 | Structure-based design | Preclinical | [180] | |
VU661013 | Fragment-based lead generation | Preclinical | [181] | |
S63845 | Structure-based design | Preclinical | [182] | |
AMG176, | Structure-based design | Phase I | [183] | |
AZD5991 | Structure-based design | Phase I | [184] | |
S64315 | Fragment-based lead generation | Phase I/II | [182] | |
Bcl-2, Mcl-1 | S1-6 | Structure-based design | Preclinical | [185] |
Nap-1 | Derivant of S1-6 | Preclinical | [186] |