p32 promotes melanoma progression and metastasis by targeting EMT markers, Akt/PKB pathway, and tumor microenvironment

CD133-Dependent Activation of Phosphoinositide 3-Kinase /AKT/Mammalian Target of Rapamycin Signaling in Melanoma Progression and Drug Resistance

Melanoma frequently harbors genetic alterations in key molecules leading to the aberrant activation of PI3K and its downstream pathways. Although the role of PI3K/AKT/mTOR in melanoma progression and drug resistance is well documented, targeting the PI3K/AKT/mTOR pathway showed less efficiency in clinical trials than might have been expected, since the suppression of the PI3K/mTOR signaling pathway-induced feedback loops is mostly associated with the activation of compensatory pathways such as MAPK/MEK/ERK. Consequently, the development of intrinsic and acquired resistance can occur. As a solid tumor, melanoma is notorious for its heterogeneity. This can be expressed in the form of genetically divergent subpopulations including a small fraction of cancer stem-like cells (CSCs) and non-cancer stem cells (non-CSCs) that make the most of the tumor mass. Like other CSCs, melanoma stem-like cells (MSCs) are characterized by their unique cell surface proteins/stemness markers and aberrant signaling pathways. In addition to its function as a robust marker for stemness properties, CD133 is crucial for the maintenance of stemness properties and drug resistance. Herein, the role of CD133-dependent activation of PI3K/mTOR in the regulation of melanoma progression, drug resistance, and recurrence is reviewed.

p32 regulates glycometabolism and TCA cycle to inhibit ccRCC progression via copper-induced DLAT lipoylation oligomerization

A key player in mitochondrial respiration, p32, often referred to as C1QBP, is mostly found in the mitochondrial matrix. Previously, we showed that p32 interacts with DLAT in the mitochondria. Here, we found that p32 expression was reduced in ccRCC and suppressed progression and metastasis in ccRCC animal models. We observed that increasing p32 expression led to an increase in oxidative phosphorylation by interacting with DLAT, thus, regulating the activation of the pyruvate dehydrogenase complex (PDHc). Mechanistically, reduced p32 expression, in concert with DLAT, suppresses PDHc activity and the TCA cycle. Furthermore, our research discovered that p32 has a direct binding affinity for copper, facilitating the copper-induced oligomerization of lipo-DLAT specifically in ccRCC cells. This finding reveals an innovative function of the p32/DLAT/copper complex in regulating glycometabolism and the TCA cycle in ccRCC. Importantly, our research provides important new understandings of the underlying molecular processes causing the abnormal mitochondrial metabolism linked to this cancer.

LncRNA NEAT1 antagonizes the inhibition of melanoma proliferation, migration, invasion and EMT by Polyphyllin B

Polyphyllin B (PPB) is a compound with anti-tumor effects. Nuclear paraspeckle assembly transcript 1 (NEAT1) is a long-stranded noncoding RNA that induces epithelial-mesenchymal transition (EMT) of tumor cells and promotes tumor growth and metastasis. However, the role and mechanism of PPB on melanoma and the correlation between them remain unclear. In this study we screened NEAT1 by using LncRNA transcriptomic sequencing, and then transfected B16F10 cells using OVER-NEAT1 lentivirus. Next, we found that PPB had significant proliferation inhibition of melanoma and B16F10 cells through MTT assay and establishment of mouse subcutaneous transplantation tumor model; in addition, through wound healing assay, transwell assay and establishment of mouse melanoma lung metastasis model, we found that PPB significantly inhibited the invasion and migration of B16F10 cells in vitro, and inhibited the metastasis of melanoma to lung, bone and liver in vivo. Finally, changes in the expression levels of EMT-related proteins were assessed by western blot (WB) and immunohistochemistry, and PPB significantly downregulated the expression levels of MMP-9, N-cadherin, etc., and upregulated E-cadherin. While overexpressed NEAT1 showed the ability to promote melanoma proliferation, migration and invasion, in addition to partially reversed the inhibition of proliferation, migration and invasion of melanoma by PPB mentioned above.

Coculture of cancer cells with platelets increases their survival and metastasis by activating the TGFβ/Smad/PAI-1 and PI3K/AKT pathways

When cancer cells enter the bloodstream, they can interact with platelets to acquire stronger survival and metastatic abilities. To elucidate the underlying mechanisms, we cocultured metastatic melanoma and triple-negative breast cancer cells with species-homologous platelets. We found that cocultured cancer cells displayed higher viabilities in circulation, stronger capacities for cell migration, invasion, and colony formation in vitro, and more tumorigenesis and metastasis in mice. RNA sequencing analysis revealed that the level of serpin family E member 1 (SERPINE1) was significantly upregulated in cocultured cancer cells. Knockdown of SERPINE1 reversed the coculture-elevated survival and metastatic phenotypes of cancer cells. Mechanistic studies indicated that coculture with platelets activated the TGFβ/Smad pathway to induce SERPINE1 expression in cancer cells, which encodes plasminogen activator inhibitor 1 (PAI-1). PAI-1 then activated PI3K to increase the phosphorylation of AKTThr308 and Bad to elevate Bcl-2, which enhanced cell survival in circulation. Moreover, higher levels of PAI-1 were detected in metastatic tumors from melanoma and triple-negative breast cancer patients than in normal tissues, and high levels of PAI-1 were associated with a shorter overall survival time and worse disease progression in breast cancer. PAI-1 may act as a potential biomarker for detecting and treating metastatic tumor cells.

Combination of niclosamide and quinacrine inactivates Akt/HK2/Cyclin D1 axis mediated by glucose deprivation towards the inhibition of melanoma cell proliferation

Malignant melanoma is one of the most aggressive and lethal skin cancer. At present, the treatment methods for melanoma have shortcomings. Glucose is the primary energy source of cancer cells. However, it is unclear whether glucose deprivation can be used to treat melanoma. Herein, we first found glucose played an essential role in melanoma proliferation. We then further found a drug combination of niclosamide and quinacrine could inhibit melanoma proliferation and glucose intake. Thirdly, we revealed the mechanism of anti-melanoma effect of the drug combination, which suppressed the Akt pathway. In addition, the first-rate limiting enzyme HK2 of glucose metabolism was inhibited. This work also disclosed that the decrease of HK2 inhibited cyclin D1 by reducing the activity of transcription factor E2F3, which further suppressed the proliferation of melanoma cells. The drug combination treatment also resulted in significant tumor regression in the absence of obvious morphologic changes in primary organ in vivo. In summary, our study demonstrated that the drug combination treatment created glucose deprivation to inactive the Akt/HK2/cyclin D1 axis, thereby inhibited the proliferation of melanoma cells, providing a potential anti-melanoma strategy.

Effective therapy with Bismuth-212 labeled macroaggregated albumin in orthotopic mouse breast tumor models

Intravascularly administered radiation therapy using beta (β-)-emitting radioisotopes has relied on either intravenously injected radiolabeled peptides that target cancer or radiolabeled microspheres that are trapped in the tumor following intra-arterial delivery. More recently, targeted intravenous radiopeptide therapies have explored the use of alpha (α)-particle emitting radioisotopes, but microspheres radiolabeled with α-particle emitters have not yet been studied. Here, FDA-approved macroaggregated albumin (MAA) particles were radiolabeled with Bismuth-212 (Bi-212-MAA) and evaluated using clonogenic and survival assays in vitro and using immune-competent mouse models of breast cancer. The in vivo biodistribution of Bi-212-MAA was investigated in Balb/c and C57BL/6 mice with 4T1 and EO771 orthotopic breast tumors, respectively. The same orthotopic breast cancer models were used to evaluate the treatment efficacy of Bi-212-MAA. Our results showed that macroaggregated albumin can be stably radiolabeled with Bi-212 and that Bi-212-MAA can deliver significant radiation therapy to reduce the growth and clonogenic potential of 4T1 and EO771 cells in vitro. Additionally, Bi-212-MAA treatment upregulated γH2AX and cleaved Caspase-3 expression in 4T1 cells. Biodistribution analyses showed 87-93% of the Bi-212-MAA remained in 4T1 and EO771 tumors 2 and 4 h after injection. Following single-tumor treatments with Bi-212-MAA there was a significant reduction in the growth of both 4T1 and EO771 breast tumors over the 18-day monitoring period. Overall, these findings showed that Bi-212-MAA was stably radiolabeled and inhibited breast cancer growth. Bi-212-MAA is an exciting platform to study α-particle therapy and will be easily translatable to larger animal models and human clinical trials.

Ultrasound molecular imaging of p32 protein translocation for evaluation of tumor metastasis

Protein translocation is an essential process for living cells to respond to different physiological, pathological or environmental stimuli. However, its abnormal occurrence usually results in undesirable outcomes such as tumors. To date, there is still a lack of appropriate methods to detect this event in live animals in a real-time manner. Here, we identified the gradually increased cell-surface translocation of p32 protein from mitochondria during tumor progression. LyP-1-modified gas vesicles (LyP-1-GVs) were developed through conjugating LyP-1 (p32-targeting peptide) to the biosynthetic GVs to monitor the cell-surface level of p32 translocation. The resulting LyP-1-GVs have about 200 nm particle size and good tumor cell targeting performance. Upon systemic administration, LyP-1-GVs can traverse through blood vessels and bind to the tumor cells, producing strong contrast imaging signals in comparison with the non-targeted GVs. The contrast imaging signals correlate well with the cell-surface translocation level of p32 protein and tumor metastatic ability. To our knowledge, this is the first report about the in vivo detection of protein translocation to cell membrane from mitochondria by ultrasound molecular imaging. Our study provides a new strategy to explore the molecular events of protein membrane translocations for evaluation of tumor metastasis at the live animal level.

gC1qR: A New Target for Cancer Immunotherapy

Although breakthroughs in cancer treatment have been achieved, immunotherapy yields only modest benefits in most patients. There is still a gap in clarifying the immune evasiveness and immune-resistance mechanisms. Identifying other candidate targets for cancer immunotherapy is therefore a clear unmet clinical need. The complement system, a pillar of innate immunity, has recently entered the limelight due to its immunoregulatory functions in the tumor microenvironment (TME). In particular, gC1qR, a receptor for globular heads of C1q, serves as a promising new target and has attracted more attention. gC1qR, also named P32/C1qBP/HABP1, is a multifunctional protein that is overexpressed in various cancers and holds prognostic value. It regulates the tumorigenic, progression and metastatic properties of tumor cells through several downstream signaling pathways, including the Wnt/β-catenin, PKC-NF-κB and Akt/PKB pathways. A few preclinical experiments conducted through gC1qR interventions, such as monoclonal antibody, chimeric antigen receptor T-cell (CAR-T) therapy, and tumor vaccination, have shown encouraging results in anticancer activity. The efficacy may rely on the regulatory role on the TME, induction of tumor cells apoptosis and antiangiogenic activity. Nevertheless, the current understanding of the relationship between cancer immunotherapy and gC1qR remains elusive and often contradictory, posing both opportunities and challenges for therapeutic translation in the clinic. In this review, we focus on the current understanding of gC1qR function in cancer immunology and highlight the vital roles in regulating the TME. We also examines the rationale behind targeting gC1qR and discusses the potential for translating into clinical practice.

C1QBP regulates mitochondrial plasticity to impact tumor progression and antitumor immune response

Mitochondrial plasticity including mitochondrial dynamics, metabolic flexibility, and mitochondrial quality control, impact tumor cells’ progression and determine immune cells’ fate. Complement C1q binding protein (C1QBP) plays an indispensable role through regulating mitochondrial morphology, metabolism, and autophagy. C1QBP promotes mitochondrial plasticity to impact tumor metastasis and their therapeutic response. At the same time, C1QBP is involved in regulating immune cells’ maturation, differentiation, and effector function through the enhancement of mitochondrial function. In this regard, manipulation of C1QBP has been shown to adjust the competitive balance between tumor cells and immune cells. In the course of evolution, mitochondrial plasticity has endowed numerous advantages against the relentless microenvironment of tumors. In this current review, we summarize the current knowledge of the mechanism of C1QBP regulation of cancer and immunity. We explain this process in vision of potentially new anticancer therapies.

An approach to p32/gC1qR/HABP1: a multifunctional protein with an essential role in cancer

P32/gC1qR/HABP1 is a doughnut-shaped acidic protein, highly conserved in eukaryote evolution and ubiquitous in the organism. Although its canonical subcellular localization is the mitochondria, p32 can also be found in the cytosol, nucleus, cytoplasmic membrane, and it can be secreted. Therefore, it is considered a multicompartmental protein. P32 can interact with many physiologically divergent ligands in each subcellular location and modulate their functions. The main ligands are C1q, hyaluronic acid, calreticulin, CD44, integrins, PKC, splicing factor ASF/SF2, and several microbial proteins. Among the functions in which p32 participates are mitochondrial metabolism and dynamics, apoptosis, splicing, immune response, inflammation, and modulates several cell signaling pathways. Notably, p32 is overexpressed in a significant number of epithelial tumors, where its expression level negatively correlates with patient survival. Several studies of gain and/or loss of function in cancer cells have demonstrated that p32 is a promoter of malignant hallmarks such as proliferation, cell survival, chemoresistance, angiogenesis, immunoregulation, migration, invasion, and metastasis. All of this strongly suggests that p32 is a potential diagnostic molecule and therapeutic target in cancer. Indeed, preclinical advances have been made in developing therapeutic strategies using p32 as a target. They include tumor homing peptides, monoclonal antibodies, an intracellular inhibitor, a p32 peptide vaccine, and p32 CAR T cells. These advances are promising and will allow soon to include p32 as part of targeted cancer therapies.