Inactivating p53 is essential for nerve growth factor receptor to promote melanoma-initiating cell-stemmed tumorigenesis

The Role of Chaperone-Mediated Autophagy in Tissue Homeostasis and Disease Pathogenesis

Chaperone-mediated autophagy (CMA) is a selective proteolytic pathway in the lysosomes. Proteins are recognized one by one through the detection of a KFERQ motif or, at least, a KFERQ-like motif, by a heat shock cognate protein 70 (Hsc70), a molecular chaperone. CMA substrates are recognized and delivered to a lysosomal CMA receptor, lysosome-associated membrane protein 2A (LAMP-2A), the only limiting component of this pathway, and transported to the lysosomal lumen with the help of another resident chaperone HSp90. Since approximately 75% of proteins are reported to have canonical, phosphorylation-generated, or acetylation-generated KFERQ motifs, CMA maintains intracellular protein homeostasis and regulates specific functions in the cells in different tissues. CMA also regulates physiologic functions in different organs, and is then implicated in disease pathogenesis related to aging, cancer, and the central nervous and immune systems. In this minireview, we have summarized the most important findings on the role of CMA in tissue homeostasis and disease pathogenesis, updating the recent advances for this Special Issue.

Unveiling the Neural Environment in Cancer: Exploring the Role of Neural Circuit Players and Potential Therapeutic Strategies

The regulation of the immune environment within the tumor microenvironment has provided new opportunities for cancer treatment. However, an important microenvironment surrounding cancer that is often overlooked despite its significance in cancer progression is the neural environment surrounding the tumor. The release of neurotrophic factors from cancer cells is implicated in cancer growth and metastasis by facilitating the infiltration of nerve cells into the tumor microenvironment. This nerve-tumor interplay can elicit cancer cell proliferation, migration, and invasion in response to neurotransmitters. Moreover, it is possible that cancer cells could establish a network resembling that of neurons, allowing them to communicate with one another through neurotransmitters. The expression levels of players in the neural circuits of cancers could serve as potential biomarkers for cancer aggressiveness. Notably, the upregulation of certain players in the neural circuit has been linked to poor prognosis in specific cancer types such as breast cancer, pancreatic cancer, basal cell carcinoma, and stomach cancer. Targeting these players with inhibitors holds great potential for reducing the morbidity and mortality of these carcinomas. However, the efficacy of anti-neurogenic agents in cancer therapy remains underexplored, and further research is necessary to evaluate their effectiveness as a novel approach for cancer treatment. This review summarizes the current knowledge on the role of players in the neural circuits of cancers and the potential of anti-neurogenic agents for cancer therapy.

Reactive Oxygen Species Regulation of Chemoresistance and Metastatic Capacity of Melanoma: Role of the Cancer Stem Cell Marker CD271

BRAF mutations are present in 30-50% of cases of cutaneous melanoma, and treatment with selective BRAF and MEK inhibitors has been introduced. However, the development of resistance to these drugs often occurs. Chemo-resistant melanoma cells show increased expression of CD271, a stem cell marker that features increased migration. Concordantly, resistance to the selective inhibitor of oncogenic BRAFV600E/K, vemurafenib, is mediated by the increased expression of CD271. It has recently been shown that the BRAF pathway leads to an overexpression of the NADPH oxidase Nox4, which produces reactive oxygen species (ROS). Here, we examined in vitro how Nox-derived ROS in BRAF-mutated melanoma cells regulates their drug sensitivity and metastatic potential. We demonstrated that DPI, a Nox inhibitor, reduced the resistance of a melanoma cell line (SK-MEL-28) and a primary culture derived from a BRAFV600E-mutated biopsy to vemurafenib. DPI treatment affected the expression of CD271 and the ERK and Akt signaling pathways, leading to a drop in epithelial-mesenchymal transition (EMT), which undoubtedly promotes an invasive phenotype in melanoma. More importantly, the scratch test demonstrated the efficacy of the Nox inhibitor (DPI) in blocking migration, supporting its use to counteract drug resistance and thus cell invasion and metastasis in BRAF-mutated melanoma.

Hypoxia Controls the Glycome Signature and Galectin-8-Ligand Axis to Promote Protumorigenic Properties of Metastatic Melanoma

The prognosis for patients with metastatic melanoma (MM) involving distant organs is grim, and treatment resistance is potentiated by tumor-initiating cells (TICs) that thrive under hypoxia. MM cells, including TICs, express a unique glycome featuring i-linear poly-N-acetyllactosamines through the loss of I-branching enzyme, β1,6 N-acetylglucosaminyltransferase 2. Whether hypoxia instructs MM TIC development by modulating the glycome signature remains unknown. In this study, we explored hypoxia-dependent alterations in MM glycome‒associated genes and found that β1,6 N-acetylglucosaminyltransferase 2 was downregulated and a galectin (Gal)-8-ligand axis, involving both extracellular and cell-intrinsic Gal-8, was induced. Low β1,6 N-acetylglucosaminyltransferase 2 levels correlated with poor patient outcomes, and patient serum samples were elevated for Gal-8. Depressed β1,6 N-acetylglucosaminyltransferase 2 in MM cells upregulated TIC marker, NGFR/CD271, whereas loss of MM cell‒intrinsic Gal-8 markedly lowered NGFR and reduced TIC activity in vivo. Extracellular Gal-8 bound preferentially to i-linear poly-N-acetyllactosamines on N-glycans of the TIC marker and prometastatic molecule CD44, among other receptors, and activated prosurvival factor protein kinase B. This study reveals the importance of hypoxia governing the MM glycome by enforcing i-linear poly-N-acetyllactosamine and Gal-8 expression. This mechanistic investigation also uncovers glycome-dependent regulation of pro-MM factor, NGFR, implicating i-linear poly-N-acetyllactosamine and Gal-8 as biomarkers and therapeutic targets of MM.

p53 Family in Resistance to Targeted Therapy of Melanoma

Metastatic melanoma is one of the most aggressive tumors, with frequent mutations affecting components of the MAPK pathway, mainly protein kinase BRAF. Despite promising initial response to BRAF inhibitors, melanoma progresses due to development of resistance. In addition to frequent reactivation of MAPK or activation of PI3K/AKT signaling pathways, recently, the p53 pathway has been shown to contribute to acquired resistance to targeted MAPK inhibitor therapy. Canonical tumor suppressor p53 is inactivated in melanoma by diverse mechanisms. The TP53 gene and two other family members, TP63 and TP73, encode numerous protein isoforms that exhibit diverse functions during tumorigenesis. The p53 family isoforms can be produced by usage of alternative promoters and/or splicing on the C- and N-terminus. Various p53 family isoforms are expressed in melanoma cell lines and tumor samples, and several of them have already shown to have specific functions in melanoma, affecting proliferation, survival, metastatic potential, invasion, migration, and response to therapy. Of special interest are p53 family isoforms with increased expression and direct involvement in acquired resistance to MAPK inhibitors in melanoma cells, implying that modulating their expression or targeting their functional pathways could be a potential therapeutic strategy to overcome resistance to MAPK inhibitors in melanoma.

Proteomic methods identified P75 as marker of poor prognosis in pleuropulmonary blastoma

OBJECTIVES

To study the causes of the rapid progression of pleuropulmonary blastoma and to identify molecular markers related to its prognosis.

MATERIALS AND METHODS

Three pairs of fresh frozen samples of pleuropulmonary blastoma tumors and adjacent normal tissues were analyzed for proteomics, focusing on the protein molecules with significantly increased expression in tumor tissues and related to the cell cycle and DNA replication. The top five protein molecules were selected and verified by immunohistochemistry. To analyze the correlation between the expression of verified protein molecules in pleuropulmonary blastoma and early recurrence/metastasis of pleuropulmonary blastoma.

RESULTS

Compared with the adjacent normal tissues, 1759 proteins were upregulated and 967 proteins were downregulated in pleuropulmonary blastoma. The top five proteins related to the cell cycle and DNA replication were ORC2, P75, Skp2, MCM4 and PCNA. However, only P75, MCM4 and PCNA were upregulated in pleuropulmonary blastoma as determined by immunohistochemistry. Further analysis showed that the expression of P75 in the recurrence/metastasis group was significantly higher than that in the no recurrence/metastasis group, while the expression of MCM4 and PCNA was not significantly different between the recurrence/metastasis group and the no recurrence/metastasis group.

CONCLUSIONS

MCM4, PCNA and P75 may all play an important role in the progression of pleuropulmonary blastoma. Among them, P75 is related to the prognosis and may be used as a marker to predict the prognosis of pleuropulmonary blastoma.

Modulating Chaperone-Mediated Autophagy and Its Clinical Applications in Cancer

Autophagy is a central mechanism for maintaining cellular homeostasis in health and disease as it provides the critical energy through the breakdown and recycling of cellular components and molecules within lysosomes. One of the three types of autophagy is chaperone-mediated autophagy (CMA), a degradation pathway selective for soluble cytosolic proteins that contain a targeting motif related to KFERQ in their amino acid sequence. This motif marks them as CMA substrate and is, in the initial step of CMA, recognised by the heat shock protein 70 (Hsc70). The protein complex is then targeted to the lysosomal membrane where the interaction with the splice variant A of the lysosomal-associated membrane protein-2 (LAMP-2A) results in its unfolding and translocation into the lysosome for degradation. Altered levels of CMA have been reported in a wide range of pathologies including many cancer types that upregulate CMA as part of the pro-tumorigenic phenotype, while in aging a decline is observed and associated with a decrease of LAMP-2 expression. The potential of altering CMA to modify a physiological or pathological process has been firmly established through genetic manipulation in animals and chemical interference with this pathway. However, its use for therapeutic purposes has remained limited. Compounds used to target and modify CMA have been applied successfully to gain a better understanding of its cellular mechanisms, but they are mostly not specific, also influence other autophagic pathways and are associated with high levels of toxicity. Here, we will focus on the molecular mechanisms involved in CMA regulation as well as on potential ways to intersect them, describe modulators successfully used, their mechanism of action and therapeutic potential. Furthermore, we will discuss the potential benefits and drawbacks of CMA modulation in diseases such as cancer.

3D Bioprinting: An Enabling Technology to Understand Melanoma

Melanoma is a potentially fatal cancer with rising incidence over the last 50 years, associated with enhanced sun exposure and ultraviolet radiation. Its incidence is highest in people of European descent and the ageing population. There are multiple clinical and epidemiological variables affecting melanoma incidence and mortality, such as sex, ethnicity, UV exposure, anatomic site, and age. Although survival has improved in recent years due to advances in targeted and immunotherapies, new understanding of melanoma biology and disease progression is vital to improving clinical outcomes. Efforts to develop three-dimensional human skin equivalent models using biofabrication techniques, such as bioprinting, promise to deliver a better understanding of the complexity of melanoma and associated risk factors. These 3D skin models can be used as a platform for patient specific models and testing therapeutics.

Inactivation of the tumor suppressor p53 by long noncoding RNA RMRP

The tumor suppressor p53 prevents tumorigenesis, while inactivation of p53 promotes cancer development and drug resistance. Here, we identify that a long noncoding RNA, the RNA component of mitochondrial RNA-processing endoribonuclease (RMRP), promotes growth and proliferation of colorectal cancer cells by inhibiting p53 activity. Mechanistically, RMRP retains SNRPA1 in the nucleus, thus preventing its lysosomal degradation. The nuclear SNRPA1 then prompts MDM2-mediated p53 ubiquitination and degradation. Remarkably, RMRP expression is induced by poly (ADP-ribose) polymerase (PARP) inhibitors, a group of targeted anticancer drugs, through the transcription factor C/EBPβ. Targeting RMRP significantly enhances sensitivity of colorectal cancer cells to PARP inhibition by reactivating p53. Our study provides a possible mechanism underling tumor resistance to PARP inhibitors.

p53 inactivation is highly associated with tumorigenesis and drug resistance. Here, we identify a long noncoding RNA, the RNA component of mitochondrial RNA-processing endoribonuclease (RMRP), as an inhibitor of p53. RMRP is overexpressed and associated with an unfavorable prognosis in colorectal cancer. Ectopic RMRP suppresses p53 activity by promoting MDM2-induced p53 ubiquitination and degradation, while depletion of RMRP activates the p53 pathway. RMRP also promotes colorectal cancer growth and proliferation in a p53-dependent fashion in vitro and in vivo. This anti-p53 action of RMRP is executed through an identified partner protein, SNRPA1. RMRP can interact with SNRPA1 and sequester it in the nucleus, consequently blocking its lysosomal proteolysis via chaperone-mediated autophagy. The nuclear SNRPA1 then interacts with p53 and enhances MDM2-induced proteasomal degradation of p53. Remarkably, ablation of SNRPA1 completely abrogates RMRP regulation of p53 and tumor cell growth, indicating that SNRPA1 is indispensable for the anti-p53 function of RMRP. Interestingly and significantly, poly (ADP-ribose) polymerase (PARP) inhibitors induce RMRP expression through the transcription factor C/EBPβ, and RMRP confers tumor resistance to PARP inhibition by preventing p53 activation. Altogether, our study demonstrates that RMRP plays an oncogenic role by inactivating p53 via SNRPA1 in colorectal cancer.

Doxorubicin/Nucleophosmin Binding Protein-Conjugated Nanoparticle Enhances Anti-leukemia Activity in Acute Lymphoblastic Leukemia Cells in vitro and in vivo

Acute lymphoblastic leukemia (ALL) is an aggressive malignancy. Adults with ALL have more than 50% relapse rates. We have previously validated that overexpression of nucleophosmin (NPM) is involved in the multidrug resistance (MDR) development during ALL; and a synthetically engineered recombinant NPM binding protein (NPMBP) has been developed in our group; NPMBP and doxorubicin (DOX) can be conjugated in a nanoparticle-based drug delivery system named DOX-PMs-NPMBP to counteract MDR during ALL. Here, we evaluated the antileukemia potential of DOX-PMs-NPMBP in resistant ALL cells. This study demonstrates that DOX-PMs-NPMBP significantly enhances chemosensitivity to DOX in ALL cells. Despite at variable concentrations, both resistant and primary ALL cells from relapsed patients were sensitive to DOX-PMs-NPMBP. In detail, the half maximal inhibitory concentration (IC50) values of DOX-PMs-NPMBP were between 1.6- and 7.0-fold lower than those of DOX in cell lines and primary ALL cells, respectively; and apoptotic cells ratio was over 2-fold higher in DOX-PMs-NPMBP than DOX. Mechanistically, p53-driven apoptosis induction and cell cycle arrest played essential role in DOX-PMs-NPMBP-induced anti-leukemia effects. Moreover, DOX-PMs-NPMBP significantly inhibited tumor growth and prolonged mouse survival of ALL xenograft models; and no systemic toxicity occurrence was observed after treatment during follow-up. In conclusion, these data indicate that DOX-PMs-NPMBP may significantly exert growth inhibition and apoptosis induction, and markedly improve DOX antileukemia activity in resistant ALL cells. This novel drug delivery system may be valuable to develop as a new therapeutic strategy against multidrug resistant ALL.

Nanoparticle encapsulation of non-genotoxic p53 activator Inauhzin-C for improved therapeutic efficacy

The tumor suppressor protein p53 remains in a wild type but inactive form in ~50% of all human cancers. Thus, activating it becomes an attractive approach for targeted cancer therapies. In this regard, our lab has previously discovered a small molecule, Inauhzin (INZ), as a potent p53 activator with no genotoxicity. Method: To improve its efficacy and bioavailability, here we employed nanoparticle encapsulation, making INZ-C, an analog of INZ, to nanoparticle-encapsulated INZ-C (n-INZ-C). Results: This approach significantly improved p53 activation and inhibition of lung and colorectal cancer cell growth by n-INZ-C in vitro and in vivo while it displayed a minimal effect on normal human Wi38 and mouse MEF cells. The improved activity was further corroborated with the enhanced cellular uptake observed in cancer cells and minimal cellular uptake observed in normal cells. In vivo pharmacokinetic evaluation of these nanoparticles showed that the nanoparticle encapsulation prolongates the half-life of INZ-C from 2.5 h to 5 h in mice. Conclusions: These results demonstrate that we have established a nanoparticle system that could enhance the bioavailability and efficacy of INZ-C as a potential anti-cancer therapeutic.

Cancer-Associated Neurogenesis and Nerve-Cancer Cross-talk

In this review, we highlight recent discoveries regarding mechanisms contributing to nerve-cancer cross-talk and the effects of nerve-cancer cross-talk on tumor progression and dissemination. High intratumoral nerve density correlates with poor prognosis and high recurrence across multiple solid tumor types. Recent research has shown that cancer cells express neurotrophic markers such as nerve growth factor, brain-derived neurotrophic factor, and glial cell-derived neurotrophic factor and release axon-guidance molecules such as ephrin B1 to promote axonogenesis. Tumor cells recruit new neural progenitors to the tumor milieu and facilitate their maturation into adrenergic infiltrating nerves. Tumors also rewire established nerves to adrenergic phenotypes via exosome-induced neural reprogramming by p53-deficient tumors. In turn, infiltrating sympathetic nerves facilitate cancer progression. Intratumoral adrenergic nerves release noradrenaline to stimulate angiogenesis via VEGF signaling and enhance the rate of tumor growth. Intratumoral parasympathetic nerves may have a dichotomous role in cancer progression and may induce Wnt-β-catenin signals that expand cancer stem cells. Importantly, infiltrating nerves not only influence the tumor cells themselves but also impact other cells of the tumor stroma. This leads to enhanced sympathetic signaling and glucocorticoid production, which influences neutrophil and macrophage differentiation, lymphocyte phenotype, and potentially lymphocyte function. Although much remains unexplored within this field, fundamental discoveries underscore the importance of nerve-cancer cross-talk to tumor progression and may provide the foundation for developing effective targets for the inhibition of tumor-induced neurogenesis and tumor progression.

The p75NTR and its carboxyl-terminal fragment exert opposing effects on melanoma cell proliferation and apoptosis via modulation of the NF-κB pathway

The p75 neurotrophin receptor (p75NTR ), a member of the tumor necrosis factor superfamily of receptors, is sensitive to proteolysis and has been observed to be expressed in various cancers. However, the roles of p75NTR and its proteolytic fragments in tumorigenesis remain incompletely understood. Here, we report that the proportion of the p75NTR carboxyl-terminal fragment (p75NTR -CTF) is much higher than that of the full-length p75NTR (p75NTR -FL) in melanoma cells. Whereas p75NTR -FL positively regulates apoptosis, p75NTR -CTF promotes cell proliferation and survival, as well as increasing sorafenib resistance in vivo and in vitro. Moreover, p75NTR -CTF activates the nuclear factor kappa B pathway and enhances the mRNA and protein levels of its downstream genes c-IAP1/2, FLIP, bFGF, IL8 and VEGF. On the contrary, p75NTR -FL inhibits these processes. Taken together, these findings demonstrate that p75NTR -CTF and p75NTR -FL have opposing functions in melanoma cells, suggesting that the ratio of the two proteins affects the balance between cell death and survival. The presence of distinct p75NTR proteolytic fragments may affect biological outcomes in tumor cells.