ΔNp63α promotes Bortezomib resistance via the CYGB-ROS axis in head and neck squamous cell carcinoma

PARP1 inhibitor niraparib exerts synergistic antimyeloma effect with bortezomib through inducing DNA damage and inhibiting DNA repair

Despite the improvements in outcomes for patients with multiple myeloma (MM) over the past decade, the disease remains incurable, and even those patients who initially respond favorably to induction therapy eventually suffer from relapse. Consequently, there is an urgent need for the development of novel therapeutic agents and strategies to enhance the treatment outcomes for patients with MM. The proteasome inhibitor bortezomib (BTZ) elicits endoplasmic reticulum (ER) stress and oxidative stress in MM cells, subsequent DNA damage, ultimately inducing cell apoptosis. Poly (ADP-ribose) polymerase 1 (PARP1) acts as a pivotal enzyme for DNA repair and thus deficient PARP1 renders cells more susceptible to DNA-damaging agents. Conceivably, targeting PARP1 may enhance BTZ-induced DNA damage and cell death in MM cells. In this study, Colony formation, CCK-8, and EdU-labeling assays were conducted to evaluate the effects on MM cell proliferation. The ZIP score was used to assess synergy. Apoptosis and intercellular ROS levels were analyzed using flow cytometry and fluorescence microscopy, respectively. Immunofluorescence and Western blot analyses were used to assess protein expression. The correlation between PARP1 expression levels and the clinical prognosis was examined by tumor-related databases and bioinformatics. The results show that PARP1 is overexpressed in patient MM cells and is associated with a poor prognosis. PARP1 inhibitor niraparib decreases MM cell growth and arrests cell cycle progression at the G2/M phase. When combined with BTZ, it synergistically increases DNA damage, inhibits proliferation, and induces apoptosis. Mechanistically, Niraparib facilitates BTZ-induced ROS elevation, causing DNA double-strand breaks (DSBs), and simultaneously inhibits lesion repair by impeding the expression of repair proteins XRCC1 (X-ray repair cross-complementing protein 1) and POLβ (DNA polymerase beta). Overall, Niraparib plus bortezomib represent a promising approach for treatment of MM.

Dysregulation of delta Np63 alpha in squamous cell carcinoma and its therapeutic targeting

The gene p63 has two isoforms -a full length transactivated isoform (TA) p63 and an amino-terminally truncated isoform, ∆Np63. DeltaNp63 alpha (∆Np63α) is the predominant splice variant of the isoform, ∆Np63 and is expressed in the basal layer of stratified epithelia. ∆Np63α that is normally essential for the epithelial lineage maintenance may be dysregulated in squamous cell carcinomas (SCCs). The pro-tumorigenic or antitumorigenic role of ∆Np63 is a highly contentious arena. ∆Np63α may act as a double-edged sword. It may either promote tumor progression, epithelial-mesenchymal transition, migration, chemoresistance, and immune-inflammatory responses, or inhibit the aforementioned phenomena depending upon cell type and tumor microenvironment. Several signaling pathways, transforming growth factor-β, Wnt and Notch, as well as epigenetic alterations involving microRNAs, and long noncoding RNAs are regulated by ∆Np63α. This review has attempted to provide an in-depth insight into the role of ∆Np63α in the development of SCCs during different stages of tumor formation and how it may be targeted for therapeutic implications.

ΔNp63α in cancer: importance and therapeutic opportunities

Our understanding of cancer and the key pathways that drive cancer survival has expanded rapidly over the past several decades. However, there are still important challenges that continue to impair patient survival, including our inability to target cancer stem cells (CSCs), metastasis, and drug resistance. The transcription factor p63 is a p53 family member with multiple isoforms that carry out a wide array of functions. Here, we discuss the critical importance of the ΔNp63α isoform in cancer and potential therapeutic strategies to target ΔNp63α expression to impair the CSC population, as well as to prevent metastasis and drug resistance to improve patient survival.

The dual role of p63 in cancer

The p53 family is made up of three transcription factors: p53, p63, and p73. These proteins are well-known regulators of cell function and play a crucial role in controlling various processes related to cancer progression, including cell division, proliferation, genomic stability, cell cycle arrest, senescence, and apoptosis. In response to extra- or intracellular stress or oncogenic stimulation, all members of the p53 family are mutated in structure or altered in expression levels to affect the signaling network, coordinating many other pivotal cellular processes. P63 exists as two main isoforms (TAp63 and ΔNp63) that have been contrastingly discovered; the TA and ΔN isoforms exhibit distinguished properties by promoting or inhibiting cancer progression. As such, p63 isoforms comprise a fully mysterious and challenging regulatory pathway. Recent studies have revealed the intricate role of p63 in regulating the DNA damage response (DDR) and its impact on diverse cellular processes. In this review, we will highlight the significance of how p63 isoforms respond to DNA damage and cancer stem cells, as well as the dual role of TAp63 and ΔNp63 in cancer.