Overexpression of p73 enhances cisplatin-induced apoptosis in HeLa cells

Rescue of p53 functions by in vitro-transcribed mRNA impedes the growth of high-grade serous ovarian cancer

BACKGROUND

The cellular tumor protein p53 (TP53) is a tumor suppressor gene that is frequently mutated in human cancers. Among various cancer types, the very aggressive high-grade serous ovarian carcinoma (HGSOC) exhibits the highest prevalence of TP53 mutations, present in >96% of cases. Despite intensive efforts to reactivate p53, no clinical drug has been approved to rescue p53 function. In this study, our primary objective was to administer in vitro-transcribed (IVT) wild-type (WT) p53-mRNA to HGSOC cell lines, primary cells, and orthotopic mouse models, with the aim of exploring its impact on inhibiting tumor growth and dissemination, both in vitro and in vivo.

METHODS

To restore the activity of p53, WT p53 was exogenously expressed in HGSOC cell lines using a mammalian vector system. Moreover, IVT WT p53 mRNA was delivered into different HGSOC model systems (primary cells and patient-derived organoids) using liposomes and studied for proliferation, cell cycle progression, apoptosis, colony formation, and chromosomal instability. Transcriptomic alterations induced by p53 mRNA were analyzed using RNA sequencing in OVCAR-8 and primary HGSOC cells, followed by ingenuity pathway analysis. In vivo effects on tumor growth and metastasis were studied using orthotopic xenografts and metastatic intraperitoneal mouse models.

RESULTS

Reactivation of the TP53 tumor suppressor gene was explored in different HGSOC model systems using newly designed IVT mRNA-based methods. The introduction of WT p53 mRNA triggered dose-dependent apoptosis, cell cycle arrest, and potent long-lasting inhibition of HGSOC cell proliferation. Transcriptome analysis of OVCAR-8 cells upon mRNA-based p53 reactivation revealed significant alterations in gene expression related to p53 signaling, such as apoptosis, cell cycle regulation, and DNA damage. Restoring p53 function concurrently reduces chromosomal instability within the HGSOC cells, underscoring its crucial contribution in safeguarding genomic integrity by moderating the baseline occurrence of double-strand breaks arising from replication stress. Furthermore, in various mouse models, treatment with p53 mRNA reduced tumor growth and inhibited tumor cell dissemination in the peritoneal cavity in a dose-dependent manner.

CONCLUSIONS

The IVT mRNA-based reactivation of p53 holds promise as a potential therapeutic strategy for HGSOC, providing valuable insights into the molecular mechanisms underlying p53 function and its relevance in ovarian cancer treatment.

APR-246 induces apoptosis and enhances chemo-sensitivity via activation of ROS and TAp73-Noxa signal in oesophageal squamous cell cancer with TP53 missense mutation

BACKGROUND

Mutations in p53, identified in 90% of oesophageal squamous cell carcinoma (ESCC), are associated with unfavourable prognosis and chemo-resistance. APR-246 induces apoptosis by restoring transcriptional ability of mutant p53, and may be a promising therapeutic agent to overcome chemo-resistance in ESCC.

METHODS

In ESCC cell lines differing in p53 status, we performed in vitro cell viability and apoptosis assays, evaluated reactive oxygen species (ROS) generation, and assessed signal changes by western blot after APR-246 administration with/without chemo-agent. Antitumour effects and signal changes were evaluated in in vivo experiments using xenograft and patient-derived xenograft (PDX) mouse models.

RESULTS

APR-246 administration induced significant apoptosis by upregulating p73 and Noxa via ROS induction in ESCC cell lines harbouring p53 missense mutations. Moreover, APR-246 plus chemotherapy exerted combined antitumour effects in ESCC with p53 missense mutations. This effect was also mediated through enhanced ROS activity, leading to massive apoptosis via upregulation of p73 and Noxa. These findings were confirmed by xenograft and PDX models with p53 mutant ESCC.

CONCLUSION

APR-246 strongly induced apoptosis by inducing ROS activity and p73-Noxa signalling, specifically in ESCC with p53 missense mutation. This antitumour effect was further enhanced by combination with 5-FU, which we first confirmed in ESCC preclinical model.

Deacetylation and methylation at histone H3 lysine 9 (H3K9) coordinate chromosome condensation during cell cycle progression

Interphasic chromatin condenses into the chromosomes in order to facilitate the correct segregation of genetic information. It has been previously reported that the phosphorylation and methylation of the N-terminal tail of histone H3 are responsible for chromosome condensation. In this study, we demonstrate that the deacetylation and methylation of histone H3 lysine 9 (H3K9) are required for proper chromosome condensation. We confirmed that H3K9ac levels were reduced, whereas H3K9me3 levels were increased in mitotic cells, via immunofluorescence and Western blot analysis. Nocodazole treatment induced G2/M arrest but co-treatment with TSA, an HDAC inhibitor, delayed cell cycle progression. However, the HMTase inhibitor, AdoX, had no effect on nocodazole-induced G2/M arrest, thereby indicating that sequential modifications of H3K9 are required for proper chromosome condensation. The expression of SUV39H1 and SETDB1, H3K9me3-responsible HMTases, are specifically increased along with H3K9me3 in nocodazole-arrested buoyant cells, which suggests that the increased expression of those proteins is an important step in chromosome condensation. H3K9me3 was highly concentrated in the vertical chromosomal axis during prophase and prometaphase. Collectively, the results of this study indicate that sequential modifications at H3K9 are associated with correct chromosome condensation, and that H3K9me3 may be relevant to the condensation of chromosome length.

Intake of grape-derived polyphenols reduces C26 tumor growth by inhibiting angiogenesis and inducing apoptosis

This study evaluated the in vivo antitumor activity of grape-derived polyphenols. BALB/c mice were subcutaneously implanted with C26 colon carcinoma cells, and 2 d later they received either solvent or red wine polyphenols (RWPs) (100 mg/kg/d, human equivalent dose approximately 500 mg/d) in the drinking water for 25 d. Wistar rats received either solvent or RWPs (100 mg/kg/d, human equivalent dose approximately 1000 mg/d) in the drinking water 1 wk before injection of azoxymethane and were studied 10 wk later. In mice, RWPs inhibited tumor growth by 31%, reduced tumor vascularization and the number of lung metastases, decreased proliferation as indicated by down-regulation of Ki67, cyclin D1, and UHRF1, and increased apoptosis as indicated by TUNEL staining and active caspase-3 levels in tumor cells. RWPs reduced expression of VEGF, matrix metalloproteinase (MMP)-2, MMP-9, and cyclooxygenase-2 and increased expression of tumor suppressor genes p16(INK4A), p53, and p73 in tumor cells. In rats, RWPs reduced by 49% the number of azoxymethane-induced aberrant crypt foci (preneoplastic lesions) in colon. Thus, RWPs effectively reduced the development of colon carcinoma tumors in vivo by blunting tumor vascularization and by inhibiting proliferation and promoting apoptosis of tumor cells subsequent to an up-regulation of tumor suppressor genes.

p73alpha regulates the sensitivity of bone marrow mesenchymal stem cells to DNA damage agents

Human bone marrow mesenchymal stem cells (MSCs) are important cell population located in bone marrow that are thought to have multiple functions in cell transplantation and gene therapy. Although in vitro experiments have demonstrated that hMSCs are resistant to apoptosis induction by DNA damage agents such as chemotherapeutic substances used in bone marrow transplantation, the molecular mechanism underlying remains unclear. p73 is highly similar to p53 and plays crucial roles in regulating DNA damage-induced apoptosis pathways. In this study, we investigated the role of p73 alpha in response to chemotherapeutic substances in cultured human bone marrow MSCs. Cellular chemosensitivity and DNA damage-induced apoptotic cell death were examined in the hMSCs with exogenously over-expressed p73 alpha. Our results showed that the expression of retrovirus-driven human p73 alpha could be successfully induced in hMSCs, the over-expression of ectopic p73 alpha resulted in a significant increase of cellular sensitivity to cisplatin. The increase of cellular apoptosis was attributed to enhanced chemosensitivity in p73 alpha infected cells. Moreover, immunoblot analysis indicated that the co-activation of pro-apoptotic factors Bax and p21 were observed in the p73 alpha infected cells after cisplatin treatment. In conclusion, our findings suggested that p73 alpha is an important determinant of cellular chemosensitivity in human bone marrow MSCs.

1alpha,25-Dihydroxyvitamin D3 potentiates cisplatin antitumor activity by p73 induction in a squamous cell carcinoma model

1alpha,25-Dihydroxyvitamin D3 (1,25D3) exhibits antitumor activity in a variety of cancers including squamous cell carcinoma (SCC). Intrinsic resistance of SCC cells to cisplatin was observed and led to the investigation into whether 1,25D3 sensitizes SCC cells to cisplatin. Pretreatment with 1,25D3 followed by cisplatin enhanced growth inhibition in SCC cells compared with 1,25D3 alone as assessed by cytotoxicity and in vitro clonogenic assays. In addition, 1,25D3 sensitized SCC cells to cisplatin-mediated apoptosis. Treatment of tumor-bearing C3H mice with 1,25D3 before cisplatin reduced clonogenic survival using in vivo excision clonogenic assay. These results were not observed in a 1,25D3-resistant SCC variant, indicating the critical role of 1,25D3 in sensitizing SCC cells to cisplatin. Further, a marked decrease in fractional tumor volume was observed when SCC tumor-bearing mice were treated with 1,25D3 before cisplatin compared with either agent administered alone. Cisplatin has been shown to modulate p73 protein level in certain cancer cells. Our data showed that p73 level was not affected by cisplatin but increased by 1,25D3 in SCC cells. Knocking down p73 by small interfering RNA protected SCC cells against 1,25D3 and cisplatin-mediated clonogenic cell kill and apoptosis. Increasing p73 protein level by knocking down UFD2a, which mediates p73 degradation, promoted 1,25D3 and cisplatin-mediated clonogenic cell kill. These results suggest that 1,25D3 potentiates cisplatin antitumor activity in vitro and in vivo in a SCC model system possibly through p73 induction and apoptosis. The combination treatment may provide a more effective therapeutic regimen in cancer treatment.

p107 acts as a tumor suppressor in pRb-deficient epidermis

The specific deletion of Rb gene in epidermis leads to altered proliferation and differentiation, but not to the development of spontaneous tumors. Our previous data have demonstrated the existence of a functional compensation of Rb loss by Rbl1 (p107) in as the phenotypic differences with respect to controls are intensified. However, the possible evolution of this aggravated phenotype, in particular in relationship with tumorigenesis, has not been evaluated due to the premature death of the double deficient mice. We have now investigated whether p107 can also act as a tumor suppressor in pRb-deficient epidermis using different experimental approaches. We found spontaneous tumor development in doubly-deficient skin grafts. Moreover, Rb-deficient keratinocytes are susceptible to Ha-ras-induced transformation, and this susceptibility is enhanced by p107 loss. Further functional analyses, including microarray gene expression profiling, indicated that the loss of p107, in the absence of pRb, produces the reduction of p53-dependent pro-apoptotic signals. Overall, our data demonstrate that p107 behaves as a tumor suppressor in epidermis in the absence of pRb and suggest novel tumor-suppressive roles for p107 in the context of functional p53 and activated Ras.

Cellular immune therapy for chronic lymphocytic leukemia

Although chemotherapy can induce complete responses in patients with chronic lymphocytic leukemia (CLL), it is not considered curative. Treated patients generally develop recurrent disease requiring additional therapy, which can cause worsening immune dysfunction, myelosuppression, and selection for chemotherapy-resistant leukemia-cell subclones. Cellular immune therapy promises to mitigate these complications and potentially provide for curative treatment. Most experience with this is in the use of allogeneic hematopoietic stem-cell transplantation (allo-HSCT), in which graft-versus-leukemia (GVL) effects can be observed and shown responsible for long-term disease-free survival. However, use of allo-HSCT for CLL is limited because of the lack of suitable donors and the treatment-related morbidity/mortality for elderly patients, who constitute the majority at risk for developing this disease. The GVL effect, however, suggests there are specific CLL-associated antigens that could be targeted in autologous cellular immune therapy. Effective strategies for this will have to overcome the disease-related acquired immune deficiency and the capacity of the leukemia-cell to induce T-cell tolerance, thereby compromising the activity of even conventional vaccines in patients with this disease. We will discuss the different strategies being developed to overcome these limitations that might provide for effective cellular immune therapy of CLL.

Itch inhibition regulates chemosensitivity in vitro

Itch is a member of the HECT family of ubiquitin E3 ligases, and regulates the stability of several proteins involved in response to genotoxic stress. We have previously shown that p73 and p63, two members of the p53 family of tumour suppressors, are targets for Itch-mediated ubiquitylation and degradation. Here, we show that depletion of Itch by RNA interference augments apoptosis upon treatment with chemotherapeutic drugs. We also show that cells with no functional p53 are more sensitive to Itch depletion, highlighting the importance that changes in levels of Itch may play in majority of cancers, where p53 is absent or mutated. Furthermore, reintroduction of Itch in fibroblasts obtained from Itch deficient mice results in reduced cell death upon DNA damage. Overall our findings suggest that inhibition of Itch potentiates the effect of chemotherapeutic drugs revealing the pharmacological potentials of targeting Itch for cancer therapy.