Porcine model elucidates function of p53 isoform in carcinogenesis and reveals novel circTP53 RNA

Recent years have seen an increasing number of genetically engineered pig models of human diseases including cancer. We previously generated pigs with a modified TP53 allele that carries a Cre-removable transcriptional stop signal in intron 1, and an oncogenic mutation TP53R167H (orthologous to human TP53R175H) in exon 5. Pigs with the unrecombined mutant allele (flTP53R167H) develop mainly osteosarcoma but also nephroblastomas and lymphomas. This observation suggested that TP53 gene dysfunction is itself the key initiator of bone tumorigenesis, but raises the question which aspects of the TP53 regulation lead to the development of such a narrow tumour spectrum. Molecular analysis of p53 revealed the presence of two internal TP53 promoters (Pint and P2) equivalent to those found in human. Consequently, both pig and human express TP53 isoforms. Data presented here strongly suggest that P2-driven expression of the mutant R167H-Δ152p53 isoform (equivalent to the human R175H-Δ160p53 isoform) and its circular counterpart circTP53 determine the tumour spectrum and play a critical role in the malignant transformation in flTP53R167H pigs. The detection of Δ152p53 isoform mRNA in serum is indicative of tumorigenesis. Furthermore, we showed a tissue-specific p53-dependent deregulation of the p63 and p73 isoforms in these tumours. This study highlights important species-specific differences in the transcriptional regulation of TP53. Considering the similarities of TP53 regulation between pig and human, these observations provide useful pointers for further investigation into isoform function including the novel circTP53 in both the pig model and human patients.

Porcine model elucidates function of p53 isoform in carcinogenesis

BackgroundThe pig has long been an important animal species for biomedical research. Recent years has also seen an increasing number of genetically engineered pig models of human diseases including cancer. We previously generated pigs with a modified TP53 allele which carries a Cre-removable transcriptional stop signal in intron 1, and an oncogenic mutation TP53R167H (orthologous to human TP53R175H and mouse Trp53R172H) in exon 5. Pigs with the unrecombined mutant allele (flTP53R167H) develop osteosarcoma (OS) in aged heterozygous and young homozygous animals. In addition, some homozygous animals also developed nephroblastomas and lymphomas. This observation suggested that TP53 gene dysfunction is itself the key initiator of tumorigenesis, but raises the question which aspects of the TP53 regulation leads to the development of such a narrow tumour spectrum, mainly OS.MethodsWe performed a series of molecular and cellular analyses to study the regulation of TP53 and its family members in both healthy tissue and tumours (n= 48) from flTP53R167H pigs. Human OS cell lines were used to prove relevance to human patients.ResultsMolecular analyses of p53 revealed the presence of two internal TP53 promoters (Pint and P2) equivalent to those found in human. Consequently, both pigs and human express TP53 isoforms. Data presented here strongly suggest that P2-driven expression of the mutant R167H-Δ152p53 isoform (equivalent to the human R175H-Δ160p53 isoform) and its circular counterpart circTP53 determine the tumour spectrum and play a critical role in the malignant transformation of bones, kidney or spleen in flTP53R167H pigs. The detection of Δ152p53 isoform mRNA in serum is indicative of tumorigenesis. Furthermore, we showed a tissue-specific p53-dependent deregulation of the p63 and p73 isoforms in these tumours.ConclusionsThis study highlights important species-specific differences in the transcriptional regulation of TP53. For the first time a circTP53 RNA was identified. Results indicate that the Δ152p53 isoform, its circular circTP53 and p53 family members, TAp63δ and TAp73δ, likely play a role in the malignant transformation of bone and other tumours. Considering the similarities of TP53 regulation between pig and human, these observations provide useful pointers for further investigation into isoform function including the novel circTP53 in both the pig model and human patients.

Invasive mole presenting as acute abdomen- a case report

Gestational trophoblastic neoplasms include the tumour spectrum of hydatidiform mole (complete and partial), invasive mole, (chorioadenoma destruens), placental site trophoblastic tumour and choriocarcinoma. Here a case is reported as invasive hydatidiform mole presenting as an acute haemoperitoneum. The patient presented with acute abdominal pain and signs of haemoperitoneum. Emergency laparatomy releaved a perforating molar pregnancy, resulting in massive haemoperitoneum. Total hysterectomy was done, 5 units blood were transfused. Serum _HCG levels regress quickly and spontaneously.Mediscope Vol. 4, No. 1: Jan 2017, Page 38-39

Case Report: Expanding the tumour spectrum associated with the Birt-Hogg-Dubé cancer susceptibility syndrome

Patients with the Birt-Hogg-Dubé cancer susceptibility syndrome are at high risk of developing renal cell carcinoma, pulmonary cysts and pneumothorax, and skin lesions called fibrofolliculomas. Here we report the case of a Birt-Hogg-Dubé patient with a primary clear cell carcinoma of the thyroid (a very rare type of thyroid cancer), and FLCN loss of heterozygosity within the tumour, providing molecular evidence for this association. Our findings expand the tumour spectrum associated with this syndrome. It is paramount to identify individuals with Birt-Hogg-Dubé so that they, and subsequently their affected relatives, can benefit from tailored cancer screening and prevention.