**7. CD29**

Through CD29 molecule, also known as integrin β1, cells adhere to extracellular compartment proteins and facilitate intracellular transmission of the cellular signal [68]. CD29 presents with 3 structural domains, the extracellular one being best represented [69].

Expression of CD29 was observed in normal and tumor colonic tissues, and a presumptive role in cellular differentiation was attributed to it, due to the activation of Erk signaling pathway [68, 69]. In normal colonic mucosa, CD29 is expressed in the lower part of the intestinal crypt [69] and is considered to be involved in intestinal proliferation [68]. However, its precise role in colon cancer is unknown [68].

At present, CD29 expression in colon cancer is only used as diagnostic marker for CSCs. Further studies are needed to evaluate its involvement in cancer progression and metastasis.
