Efficient Generation of P53 Biallelic Mutations in Diannan Miniature Pigs Using RNA-Guided Base Editing

The base editing 3 (BE3) system, a single-base gene editing technology developed using CRISPR/Cas9n, has a broad range of applications for human disease model construction and gene therapy, as it is highly efficient, accurate, and non-destructive. P53 mutations are present in more than 50% of human malignancies. Due to the similarities between humans and pigs at the molecular level, pig models carrying P53 mutations can be used to research the mechanism of tumorigenesis and improve tumor diagnosis and treatment. According to pathogenic mutations of the human P53 gene at W146* and Q100*, sgRNAs were designed to target exon 4 and exon 5 of the porcine P53 gene. The target editing efficiencies of the two sgRNAs were 61.9% and 50.0%, respectively. The editing efficiency of the BE3 system was highest (about 60%) when C (or G) was at the 5th base. Puromycin screening revealed that 75.0% (21/28) and 68.7% (22/32) of cell colonies contained a P53 mutation at sgRNA-Exon5 and sgRNA-Exon4, respectively. The reconstructed embryos from sgRNA-Exon5-5# were transferred into six recipient gilts, all of which aborted. The reconstructed embryos from sgRNA-Exon4-7# were transferred into 6 recipient gilts, 3 of which became pregnant, resulting in 14 live and 3 dead piglets. Sequencing analyses of the target site confirmed 1 P53 monoallelic mutation and 16 biallelic mutations. The qPCR analysis showed that the P53 mRNA expression level was significantly decreased in different tissues of the P53 mutant piglets (p < 0.05). Additionally, confocal microscopy and western blot analysis revealed an absence of P53 expression in the P53 mutant fibroblasts, livers, and lung tissues. In conclusion, a porcine cancer model with a P53 point mutation can be obtained via the BE3 system and somatic cell nuclear transfer (SCNT).

Regulation of p53 and Cancer Signaling by Heat Shock Protein 40/J-Domain Protein Family Members

Heat shock proteins (HSPs) are molecular chaperones that assist diverse cellular activities including protein folding, intracellular transportation, assembly or disassembly of protein complexes, and stabilization or degradation of misfolded or aggregated proteins. HSP40, also known as J-domain proteins (JDPs), is the largest family with over fifty members and contains highly conserved J domains responsible for binding to HSP70 and stimulation of the ATPase activity as a co-chaperone. Tumor suppressor p53 (p53), the most frequently mutated gene in human cancers, is one of the proteins that functionally interact with HSP40/JDPs. The majority of p53 mutations are missense mutations, resulting in acquirement of unexpected oncogenic activities, referred to as gain of function (GOF), in addition to loss of the tumor suppressive function. Moreover, stability and levels of wild-type p53 (wtp53) and mutant p53 (mutp53) are crucial for their tumor suppressive and oncogenic activities, respectively. However, the regulatory mechanisms of wtp53 and mutp53 are not fully understood. Accumulating reports demonstrate regulation of wtp53 and mutp53 levels and/or activities by HSP40/JDPs. Here, we summarize updated knowledge related to the link of HSP40/JDPs with p53 and cancer signaling to improve our understanding of the regulation of tumor suppressive wtp53 and oncogenic mutp53 GOF activities.

Sex- and Mutation-Specific p53 Gain-of-Function Activity in Gliomagenesis

In cancer, missense mutations in the DNA-binding domain of TP53 are common. They abrogate canonical p53 activity and frequently confer gain-of-oncogenic function (GOF) through localization of transcriptionally active mutant p53 to noncanonical genes. We found that several recurring p53 mutations exhibit a sex difference in frequency in patients with glioblastoma (GBM). In vitro and in vivo analysis of three mutations, p53R172H, p53Y202C, and p53Y217C, revealed unique interactions between cellular sex and p53 GOF mutations that determined each mutation's ability to transform male versus female primary mouse astrocytes. These phenotypic differences were correlated with sex- and p53 mutation–specific patterns of genomic localization to the transcriptional start sites of upregulated genes belonging to core cancer pathways. The promoter regions of these genes exhibited a sex difference in enrichment for different transcription factor DNA-binding motifs. Together, our data establish a novel mechanism for sex-specific mutant p53 GOF activity in GBM with implications for all cancer. Significance: Sex differences in cancer, including glioblastoma, have been observed in both incidence and outcome. We reveal that TP53, the most commonly mutated gene in cancer, contributes to sex differences through differential GOF activity. This discovery has critical implications for our understanding of p53 mutations and the importance of sex as a biological variable.

Recent Advances of WEE1 Inhibitors and Statins in Cancers With p53 Mutations

p53 is among the most frequently mutated tumor suppressor genes given its prevalence in &gt;50% of all human cancers. One critical tumor suppression function of p53 is to regulate transcription of downstream genes and maintain genomic stability by inducing the G1/S checkpoint in response to DNA damage. Tumor cells lacking functional p53 are defective in the G1/S checkpoint and become highly dependent on the G2/M checkpoint to maintain genomic stability and are consequently vulnerable to Wee1 inhibitors, which override the cell cycle G2/M checkpoint and induce cell death through mitotic catastrophe. In addition to the lost tumor suppression function, many mutated p53 (Mutp53) proteins acquire gain-of-function (GOF) activities as oncogenes to promote cancer progression, which manifest through aberrant expression of p53. In cancer cells with GOF Mutp53, statins can induce CHIP-mediated degradation of Mutp53 within the mevalonate pathway by blocking the interaction between mutp53 and DNAJA1. Therefore, targeting critical downstream pathways of Mutp53 provides an alternative strategy for treating cancers expressing Mutp53. In this review, we summarize recent advances with Wee1 inhibitors, statins, and mevalonate pathway inhibitors in cancers with p53 mutations.

p53 mutations exhibit sex specific gain-of-function activity in gliomagenesis

The tumor suppressor TP53 is the most frequently mutated gene in cancer. Most TP53 mutations are missense mutations in the DNA-binding domain, which in addition to loss of canonical p53 activity, frequently confer gain-of-function (GOF) aberrant transcriptional activity through mutant p53 localization to non-canonical genes. GOF phenotypes differ by mutation and cell identity and are reported to include increased proliferation, migration, metabolic reprogramming, and therapy resistance. We found that several recurring p53 mutations exhibit a sex-bias in patients with glioblastoma (GBM). In vitro and in vivo analysis of three mutations, p53R172H, p53Y202C, and p53Y217C revealed sex differences in each mutation′s ability to transform primary mouse astrocytes. p53R172H exhibited a far greater ability to transform female astrocytes than males, p53Y202C transformed both male and female astrocytes with a small male bias, and p53Y217C only exhibited GOF transformation effects in male astrocytes. These phenotypic differences reflect an interaction between sex and GOF mutation to drive unique gene expression patterns in cancer pathways. We found that mutant p53 exhibits sex and mutation specific aberrant genomic localization to the transcriptional start sites of upregulated genes, whose promoter regions were enriched for different sets of transcription factor DNA-binding motifs. Together, our data establish a novel paradigm for sex specific mutant p53 GOF activity in GBM with implications for all cancer.

Alterations of epigenetic regulators and P53 mutations in murine mesenchymal stem cell cultures: A possible mechanism of spontaneous transformation

BACKGROUND: Recent studies demonstrated the involvement of mesenchymal stem/stromal cells (MSCs) in carcinogenesis, but the molecular mechanism behind this transformation is still obscured. OBJECTIVE: To screen both the expression levels of polycomb and trithorax epigenetic regulators and TrP53 mutations in early and late MSC culture passages in an attempt to decipher the mechanism of spontaneous transformation. METHODS: The study was conducted on early and late passages of MSC culture model from C57BL/6J mice. The expression profile of 84 epigenetic regulators was examined using RT2 profiler PCR array. TrP53 mutations in the DNA binding domain was screened. Codons, amino acids positions and the corresponding human variants were detected in P53 sequences. RESULTS: Sixty-two epigenetic regulators were dysregulated. Abnormalities were detected starting the third passage. Nine regulators were dysregulated in all passages. (C>G) substitution P53 mutation was detected in passage 3 resulting in Ser152Arg substitution. Passages 6, 9, 12 and the last passage showed T>C substitution resulting in Cys235Arg substitution. The last passage had T deletion and A insertion resulting in frame shift mutations changing the p.Phe286Ser and p.Asn103Lys respectively. CONCLUSION: In vitro expanded MSCs undergo transformation through alteration of epigenetic regulators which results in genomic instability and frequent P53 mutations.

The Gain-of-Function p53 R248W Mutant Promotes Migration by STAT3 Deregulation in Human Pancreatic Cancer Cells

Missense p53 mutations (mutp53) occur in approx. 70% of pancreatic ductal adenocarcinomas (PDAC). Typically, mutp53 proteins are aberrantly stabilized by Hsp90/Hsp70/Hsp40 chaperone complexes. Notably, stabilization is a precondition for specific mutp53 alleles to acquire powerful neomorphic oncogenic gain-of-functions (GOFs) that promote tumor progression in solid cancers mainly by increasing invasion and metastasis. In colorectal cancer (CRC), we recently established that the common hotspot mutants mutp53R248Q and mutp53R248W exert GOF activities by constitutively binding to and hyperactivating STAT3. This results in increased proliferation and invasion in an autochthonous CRC mouse model and correlates with poor survival in patients. Comparing a panel of p53 missense mutations in a series of homozygous human PDAC cell lines, we show here that, similar to CRC, the mutp53R248W protein again undergoes a strong Hsp90-mediated stabilization and selectively promotes migration. Highly stabilized mutp53 is degradable by the Hsp90 inhibitors Onalespib and Ganetespib, and correlates with growth suppression, possibly suggesting therapeutic vulnerabilities to target GOF mutp53 proteins in PDAC. In response to mutp53 depletion, only mutp53R248W harboring PDAC cells show STAT3 de-phosphorylation and reduced migration, again suggesting an allele-specific GOF in this cancer entity, similar to CRC. Moreover, mutp53R248W also exhibits the strongest constitutive complex formation with phosphorylated STAT3. The selective mutp53R248W GOF signals through enhancing the STAT3 axis, which was confirmed since targeting STAT3 by knockdown or pharmacological inhibition phenocopied mutp53 depletion and reduced cell viability and migration preferentially in mutp53R248W-containing PDAC cells. Our results confirm that mutp53 GOF activities are allele specific and can span across tumor entities.

Relationship between Lung Carcinogenesis and Chronic Inflammation in Rodents

Lung cancer remains the leading cause of cancer-related deaths, with an estimated 1.76 million deaths reported in 2018. Numerous studies have focused on the prevention and treatment of lung cancer using rodent models. Various chemicals, including tobacco-derived agents induce lung cancer and pre-cancerous lesions in rodents. In recent years, transgenic engineered rodents, in particular, those generated with a focus on the well-known gene mutations in human lung cancer (KRAS, EGFR, and p53 mutations) have been widely studied. Animal studies have revealed that chronic inflammation significantly enhances lung carcinogenesis, and inhibition of inflammation suppresses cancer progression. Moreover, the reduction in tumor size by suppression of inflammation in animal experiments suggests that chronic inflammation influences the promotion of tumorigenesis. Here, we review rodent lung tumor models induced by various chemical carcinogens, including tobacco-related carcinogens, and transgenics, and discuss the roles of chronic inflammation in lung carcinogenesis.

Recent Advances of Wee1 Inhibitors and Statins in Gynecologic Cancers with p53 Mutations

p53 is among the most frequently mutated tumor suppressor genes given its prevalence in &gt;50% of all human cancers, including high grade serous endometrial cancers and ovarian cancers. In addition to loss of tumor suppression function, many mutated p53 (Mutp53) proteins acquire gain-of-function (GOF) activities as oncogenes to promote cancer progression, which manifest through aberrant expression of p53. As we have come to see, statins induce CHIP-mediated degradation of mutp53 by blocking the interaction between mutp53 and DNAJA1. Therefore, targeting critical downstream pathways of mutp53 provides an alternative strategy for treating cancers expressing mutp53. In this review, we summarize recent advances with Wee1 inhibitors and mevalonate pathway inhibitors, particularly statins, regarding their use in gynecological cancers with p53 mutations.