Renal cell carcinoma escapes death by p53 depletion through transglutaminase 2-chaperoned autophagy

Abstract

In renal cell carcinoma, transglutaminase 2 (TGase 2) crosslinks p53 in autophagosomes, resulting in p53 depletion and the tumor's evasion of apoptosis. Inhibition of TGase 2 stabilizes p53 and induces tumor cells to enter apoptosis. This study explored the mechanism of TGase 2-dependent p53 degradation. We found that TGase 2 competes with human double minute 2 homolog (HDM2) for binding to p53; promotes autophagy-dependent p53 degradation in renal cell carcinoma (RCC) cell lines under starvation; and binds to p53 and p62 simultaneously without ubiquitin-dependent recognition of p62. The bound complex does not have crosslinking activity. A binding assay using a series of deletion mutants of p62, p53 and TGase 2 revealed that the PB1 (Phox and Bem1p-1) domain of p62 (residues 85–110) directly interacts with the β-barrel domains of TGase 2 (residues 592–687), whereas the HDM2-binding domain (transactivation domain, residues 15–26) of p53 interacts with the N terminus of TGase 2 (residues 1–139). In addition to the increase in p53 stability due to TGase 2 inhibition, the administration of a DNA-damaging anti-cancer drug such as doxorubicin-induced apoptosis in RCC cell lines and synergistically reduced tumor volume in a xenograft model. Combination therapy with a TGase 2 inhibitor and a DNA-damaging agent may represent an effective therapeutic approach for treating RCC.

A Precision Strategy to Cure Renal Cell Carcinoma by Targeting Transglutaminase 2

“…Although this ensemble of data regarding ccRCC may explain why ccRCC shows resistance to therapeutics, it did not identify any specific therapeutic target for ccRCC. Although transglutaminase 2 (TGase 2) expression is reported to be high in ccRCC, and TGase 2 inhibition showed significant potential for a therapeutic approach for ccRCC in a series of past studies [19][20][21][22][23], the CPTAC study did not reveal any significance of TGase 2 in ccRCC [18]. These analytical results did not seem to fit, in the overall effort to find a cure for ccRCC.…”

Transglutaminase 2, a double face enzyme

“…Furthermore, in differentiation-induced BRAF-mutated human melanoma cells, it is not the expression of the enzyme that is increased, but rather its activity, as recently reported (Tabolacci et al 2016). Another interesting case is represented by clear cell renal carcinoma (CCRC) which is characterized by high expression of Tgase2, whose main target in this tumor is p53, which is crosslinked by the enzyme and addressed for degradation via autophagy (Kang et al 2016). p53 is a well-known oncogene suppressor, and its degradation prevents apoptosis and favors conversely tumor survival and growth (Kang et al 2016).…”

“…Within this frame, it is hypothesized that Tgase can, by interacting with BAX via its BH3-domain, control the release of cytochrome c and apoptosisinducing factor (AIF) from mitochondria leading to both caspase-dependent and -independent cell death pathways (Rodolfo et al 2004;Yoo et al 2012). In this context, the role played by Tgase2 in the process of autophagy which is deficient in cells lacking Tgase2 is also important (D'Eletto et al 2010(D'Eletto et al , 2012Altuntas et al 2015;Kang et al 2016). Another interesting novel aspect of the presence of Tgase2 at the mitochondrial level is its involvement in the energy metabolism.…”

“…Another interesting case is represented by clear cell renal carcinoma (CCRC) which is characterized by high expression of Tgase2, whose main target in this tumor is p53, which is crosslinked by the enzyme and addressed for degradation via autophagy (Kang et al 2016). p53 is a well-known oncogene suppressor, and its degradation prevents apoptosis and favors conversely tumor survival and growth (Kang et al 2016). In addition, it must be mentioned that also the metabolism of cancer cells is apparently dependent on the action of Tgase2, as it happens in mammary cancer, in which expression and activity of Tgase2 is eventually relevant for triggering the Warburg effect (Kumar et al 2014;Rossin et al 2015) through NFκB and HIF signaling and more recently through its interplay with PKM2 a key rate limiting enzyme of glycolysis (Altuntas et al 2015).…”

Identification of novel prognostic alternative splicing signature in papillary renal cell carcinoma

“…The yellow diamonds represent the prognostic SFs. 49 In addition, oxidative phosphorylation was considered a vital behavior related to apoptosis which could induce cell death in cancers. In addition, the red lines indicate the positive correlation while the blue lines indicate the negative correlation.…”