Could gastrointestinal tumor-initiating cells originate from cell-cell fusion in vivo?

Table 2 Molecules potentially involved in gastrointestinal tumor-initiating cell generation from cell-cell fusion

Tumor type	Cell surface molecules involved in cell fusion	Intracellular molecules involved in cell fusion	Signaling pathways involved in cell fusion	giTIC molecules
Gastric	CD44, CD133, EpCAM, CXCR4, Lgr5, CD54[3], ALDH1[3]	OCT4, SOX2[120], Twist, Slug[47], Nanog, Lin28[44]	CXCL12/CXCR4, Lgr5[3]	CD44[3], CD133[111]
Colorectal	CD44, CD133, EpCAM, CXCR4, CD166[3]. CD81, CD9, GTP-binding protein α13, radixin[85], Syncytin 1, CD47	APC, p53, Kras, NF-κB, OCT4, SOX2[3]. ADAM10, myosin regulatory light chain, RhoA[85]	CXCL12/CXCR4, Wnt/β-catenin[3], c-Jun	CD133, CD44, ALDH1, EpCAM, CD44, CD166, CD24, LGR5, CD26[3]
Liver	CD44, CD133, CD13, EpCAM, CD24, CD90[3], E-cadherin, matrix metalloproteinase	p53[3], OCT4, SOX2[119]. Vimentin, Twist, Snail[113]	CXCL12/CXCR4[77], Wnt, TGF-β, Notch, Hedgehog[3]	CD133, CD49f, CD90, CD13[3]
Esophageal	CD44, CD133, EpCAM[115], CXCR4[3]	OCT4, SOX2	Lgr5[3], CXCL12/CXCR4	CD44, ALDH1[3]
Pancreatic	CD44, CD133, EpCAM, CXCR4, CD24[3], ALDH1[3]	KRAS, TP53, SMAD4, OCT4, SOX2[116]	CXCL12/CXCR4[3], Lgr5[118]	CD133, CD44, CD24, ESA, CXCR4[3]

giTIC: Gastrointestinal tumor-initiating cell; CD44 and CD133: Cell surface glycoproteins; CXCL12: Chemokine; CXCR4: Chemokine receptors 4; EpCAM: Epithelial cell adhesion molecule, transmembrane glycoprotein; ALDH: Acetaldehyde dehydrogenase; NF-κB: Nuclear factor kappa-B; APC: Adenomatous polyposis coli; GTP: Guanosine triphosphate; ESA: Epithelial-specific antigen; TGF-β: Transforming growth factor-β.