Altered Expression of Shorter p53 Family Isoforms Can Impact Melanoma Aggressiveness

Abstract

Cutaneous melanoma is the most aggressive form of skin cancer. Despite the significant advances in the management of melanoma in recent decades, it still represents a challenge for clinicians. The TP53 gene, the guardian of the genome, which is altered in more than 50% of human cancers, is rarely mutated in melanoma. More recently, researchers started to appreciate the importance of shorter p53 isoforms as potential modifiers of the p53-dependent responses. We analyzed the expression of p53 and p73 isoforms both at the RNA and protein level in a panel of melanoma-derived cell lines with different TP53 and BRAF status, in normal conditions or upon treatment with common anti-cancer DNA damaging agents or targeted therapy. Using lentiviral vectors, we also generated stable clones of H1299 p53 null cells over-expressing the less characterized isoforms Δ160p53α, Δ160p53β, and Δ160p53γ. Further, we obtained two melanoma-derived cell lines resistant to BRAF inhibitor vemurafenib. We observed that melanoma cell lines expressed a wide array of p53 and p73 isoforms, with Δ160p53α as the most variable one. We demonstrated for the first time that Δ160p53α, and to a lesser extent Δ160p53β, can be recruited on chromatin, and that Δ160p53γ can localize in perinuclear foci; moreover, all Δ160p53 isoforms can stimulate proliferation and in vitro migration. Lastly, vemurafenib-resistant melanoma cells showed an altered expression of p53 and p73 isoforms, namely an increased expression of potentially pro-oncogenic Δ40p53β and a decrease in tumor-suppressive TAp73β. We therefore propose that p53 family isoforms can play a role in melanoma cells’ aggressiveness.

Cytoplasmic p53β Isoforms Are Associated with Worse Disease-Free Survival in Breast Cancer

“…This may explain why p53β-positive staining was found in both cellular compartments in this study. Both Δ133p53α and Δ160p53α have been described to localise in the nucleus with minor staining in the cytoplasm; however, Δ160p53α can also present peri nucleolar localisation [ 4 , 5 , 40 ]. This indicates that these isoforms may be travelling between the cytoplasm and the nucleus; however, isoform translocation within cellular compartments could depend on the cellular context (e.g., in response to DNA damage).…”

“…Plasmid vectors for full-length wild-type p53 (pRcCMV-p53WT) were generously provided by Prof. Helen Rizos (Department of Biomedical Sciences, Macquarie University, Sydney, Australia). The constructs for p53β (pSV40-p53β), Δ133p53 (pSV40133-p53), Δ160p53 (pCDNA3.1-Δ160p53α) and the control vector pSV40 were kindly provided by Dr. Jean-Christophe Bourdon (Cellular Medicine, School of Medicine, The University of Dundee, Dundee, Scotland, UK) and have been previously described [ 4 , 12 , 40 , 52 ].…”

p53 and Its Isoforms in Renal Cell Carcinoma—Do They Matter?

“…Additionally, the controlled modulation of the expression pattern of p53 isoforms, by antisense oligonucleotides at the RNA level [ 53 , 57 ], and by small molecules at the protein level [ 68 ], which could be an alternative approach in anti-cancer therapy applied in RCC in the future. Moreover, monitoring of changes in expression profiles of the specific isoforms including p53β, p53γ, Δ133p53, and Δ160p53 might be applied in a personalized medicine to increase therapy effectiveness [ 33 , 63 , 65 ]. Altogether, p53 and its isoforms seem to mediate cell response and cell sensitivity to treatment in renal cell carcinoma; however, more research is needed to better understand the role of network interactions between p53 and its isoforms with other proteins and RNAs in this cancer.…”

“…It has also been demonstrated that the Δ133p53 protein is engaged in carcinogenesis, including angiogenesis and metastasis, as well as in cellular events, including proliferation, cellular senescence, and apoptosis [ 56 , 60 , 61 ]. The Δ160p53 isoform’s second protein product, which is synthesized from a P2-initiated transcript, has been detected in several cell lines endogenously expressing different mutant p53s [ 62 , 63 ]. Moreover, wild-type p53 cell lines (HCT116, U2OS, and A549) show either no signs or low levels of Δ160p53 expression [ 64 ].…”

“…It seems that Δ160p53 is expressed mostly in mutant p53 cells promoting tumorigenesis [ 64 ]. It has also been shown that higher levels of Δ160p53 expression in melanoma patients are associated with cancer aggressiveness [ 63 ].…”