Numerous studies on the potential link between FAK and different kinds of cancer have gradually revealed the biological mechanisms by which FAK promotes the development and progression of cancer [
1]. FAK is a tyrosine kinase with a molecular weight of 125kD, playing a vital role in cellular communication, especially in cell signaling systems [
2]. Wang et al. [
3] revealed that increased mRNA levels, protein levels, and the activation of FAK were positively associated with cancer metastasis and invasion and frequently inversely correlated with better clinical cancer sample results in the detection of human cancer samples. Relevant studies have found that FAK was overexpressed and/or over-phosphorylated in multiple cancer cells, responsible for cell migration [
4], survival [
5], proliferation [
6], and adhesion [
7]. In addition, FAK is strongly associated with the occurrence and development of tumors [
2,
8] and regarded as a functional protein in the cytoplasm, typically functioning in a kinase-dependent manner [
9]. Firstly, FAK receives different extracellular signals coming from cell-surface transmembrane receptors including integrins, cytokines, growth factors, and G protein-coupled receptors. After that, FAK activates and triggers subsequent signaling cascades in a variety of cellular activities [
10,
11]. FAK can also participate in the signal transduction process in tumor vessel, mediating the vessel permeability [
12‐
14]. The FERM domain of FAK can combine with the cytoplasmic region of vascular endothelial calcium mucin. It is important for cell-cell adhesive junctional structures, an integral part of keeping vascular integrity [
15]. Furthermore, FAK is essential for maintaining vascular functions in tumor angiogenesis. Lees et al. [
16] found that FAK recovered the vascular leakage defect through the activation of kinase domain. And it is a fact that cytokines induce vascular growth factor expression by the FAK signaling pathway. For example, via Src-FAK-STAT3 signaling, IL-6 induces VEGF-C expressions [
17]. As a result, FAK kinase activity is required for tumor growth [
18], angiogenesis [
17], and vascular permeability [
19]. These show that FAK is a typical multifunctional protein which integrates and transduces signals into cancer cells via integrin or growth factor receptors. Tumor stem cells are few tumor cells which are present in malignant cells and believed to be the source of cancer cells. They have the ability to proliferate, self-renew and generate heterogeneous tumor cells, maintaining the vitality of the tumor cell population [
20,
21]. Yoon et al. [
22] found that FAK promoted cancer stem cells (CSCs) renewal and drug resistance by functioning in survival signaling. For example, FAK and the extracellular signal-regulated kinase (ERK1/2) pathway are involved in the regulation of growth and metastasis of liver cancer stem cells (LCSCs) [
23]. The use of the anticancer drug salinomycin inhibited the activity of FAK and ERK1/2, resulting in the increased stiffness of LCSCs [
24]. Another study has shown that changes in the stiffness of living cells might affect numerous cellular physiological activities [
25]. FAK can affect the growth of LCSCs through this mechanism of the regulation of cell stiffness. Cheng et al. [
26] targeted HIC1 and RassF1A methylation, induced the transformation of mesenchymal stem cells (MSCs) and the cell stiffness was lost. It is suggested that Tumor cells are softer than normal cells, mainly due to loss of cytoskeletal support [
27,
28]. And the loss of stiffness can represent a phenotype of tumor development which facilitates cancer cell migration and adapts to other tissues [
29,
30]. Taken together, these results indicate that FAK is closely related to biological behaviors such as survival, migration, invasion, and proliferation of CSCs. Based on those findings, FAK can be regarded as a target for cancer therapy.
Actually, investigators have found that FAK was also functional in the nucleus [
31]. FAK can enter the nucleus and regulates gene expression to influence tumorigenesis [
32]. In the nucleus, activated FAK binds to transcription factors to regulate gene expression. Inactive FAK synergizes with different E3 ligases to promote the turnover of transcription factors [
33]. FAK affects tumor survival and growth by altering the transcription [
34]. In this review, some regulation modes of nuclear FAK are discussed. We focus on nuclear FAK regulating gene expression in different cancer cells. FAK regulates gene expression by affecting the expression of transcription factors. Furthermore, we emphasize that nuclear FAK also has an important role in the study of cancer, which is positively related to the occurrence and development of tumors.