NAD pool as an antitumor target against cancer stem cells in head and neck cancer

Targeting NAD + biosynthesis suppresses TGF-β1/Smads/RAB26 axis and potentiates cisplatin cytotoxicity in non-small cell lung cancer brain metastasis

Nicotinamide adenine dinucleotide (NAD+) plays an important role in tumor progression, but its role in non-small cell lung cancer with brain metastasis (NSCLC BM) remains unclear. Herein, we investigated NAD+ biosynthesis targeting as a new therapeutic strategy for NSCLC BM. Therapeutic activity of nicotinamide phosphoribosyl transferase (NAMPT) inhibitors was evaluated in mouse models of NSCLC BM and using various assays such as NAD+ quantitation, cell viability, and apoptosis assays. To explore impact on downstream signaling, RNA sequencing was used in NAMPT inhibitor-treated and control cells, followed by validation with genetic knockdown, western blot and qRT-PCR. Expression of NAMPT and downstream proteins in human NSCLC BM and its association with patient prognosis were examined. Finally, combination of NAMPT inhibitor and cisplatin was tested in vivo. Systemic treatment with NAMPT inhibitors demonstrated intracranial activity in an NSCLC BM model. NAMPT inhibitors decreased cellular NAD levels and suppressed proliferation and invasion, and induced apoptosis in NSCLC cells. Supplementation with NAD+ precursor NMN rescued these NAMPT inhibitor effects. Mechanistically, disruption of NAMPT-mediated NAD+ biosynthesis suppressed TGF-β1/Smads/RAB26 signaling, leading to inhibition of NSCLC cells. Expression of NAMPT/TGF-β1/Smads/RAB26 axis proteins was upregulated in NSCLC BM tissues and correlated with poor prognosis. Combining NAMPT inhibitors with cisplatin further extended the survival of NSCLC BM-bearing mice. Targeting NAD+ biosynthesis provides a new therapeutic strategy for NSCLC BM and can be effectively combined with cisplatin. Our studies identified the TGF-β1/Smads/RAB26 signaling downstream of NAMPT, which was targeted by NAMPT inhibition to mediate anti-cancer effects.

Tumor-associated macrophages drive heterogenetic CD10High cancer stem cells to implement tumor-associated neutrophils reprogramming in oral squamous cell carcinoma

Tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) widely participate in the malignant progression in cancer. Previously, we have demonstrated that M1-like TAMs cascaded a stem-like phenotype of oral squamous cell carcinoma (OSCC). Yet, the underlying mechanisms still need to be demonstrated for the regulation of TAMs on cancer stem cells (CSCs) in OSCC. In this study, we investigated a group of CSCs with increased expression of cluster differentiation 10 (CD10), which acted as a mediator in the interaction network between TAMs and tumor-associated neutrophils (TANs) in OSCC. The results showed a significant association between TAMs infiltrations and increased expression of CD10 among all the CSCs-related molecules in OSCC. Then, we validated that OSCC cells with high CD10 expression possessed increased CSCs characteristics. TAMs could drive the heterogenetic CD10High CSCs by activating the IL6/STAT3/CD10 pathway. Furthermore, CD10High CSCs could recruit and reprogram tumor-associated neutrophils (TANs) in an immunosuppressive state by secreting S100A8/A9 in OSCC. These finding indicated that CD10High CSCs played great roles in signaling crosstalk between TAMs and TANs in OSCC, by which infiltrated TAMs drive CD 10High CSCs to recruit and reprogram TANs in an immunosuppressive state. Herein, we managed to demonstrate that TAMs could directly regulate a heterogenetic cluster of CSCs with high CD10 expression, and CD10High CSCs could recruit and reprogram TANs in OSCC. The novel crosstalk among OSCC-TAMs-CD10High CSCs-TANs might bring new prospects for improving the treatment strategies for OSCC patients.

Fertility protection during chemotherapy treatment by boosting the NAD(P)+ metabolome

Chemotherapy induced ovarian failure and infertility is an important concern in female cancer patients of reproductive age or younger, and non-invasive, pharmacological approaches to maintain ovarian function are urgently needed. Given the role of reduced nicotinamide adenine dinucleotide phosphate (NADPH) as an essential cofactor for drug detoxification, we sought to test whether boosting the NAD(P)+ metabolome could protect ovarian function. We show that pharmacological or transgenic strategies to replenish the NAD+ metabolome ameliorates chemotherapy induced female infertility in mice, as measured by oocyte yield, follicle health, and functional breeding trials. Importantly, treatment of a triple-negative breast cancer mouse model with the NAD+ precursor nicotinamide mononucleotide (NMN) reduced tumour growth and did not impair the efficacy of chemotherapy drugs in vivo or in diverse cancer cell lines. Overall, these findings raise the possibility that NAD+ precursors could be a non-invasive strategy for maintaining ovarian function in cancer patients, with potential benefits in cancer therapy.

Supplementation with NAD+ and its precursors: A rescue of female reproductive diseases

Nicotinamide adenine dinucleotide (NAD+) is an essential coenzyme involved in many pathophysiological processes. Supplementation with NAD+ and its precursors has been demonstrated as an emerging therapeutic strategy for the diseases. NAD+ also plays an important role in the reproductive system. Here, we summarize the function of NAD+ in various reproductive diseases and review the application of NAD+ and its precursors in the preservation of reproductive capacity and the prevention of embryonic malformations. It is shown that NAD+ shows good promise as a therapeutic approach for saving reproductive capacity.

The role of nicotinamide adenine dinucleotide salvage enzymes in cardioprotection

The increasing trend of cardiac diseases is becoming a major threat globally. Cardiac activities are based on integrated action potential through electronic flux changes within intra- and extracellular molecular activities. Nicotinamide adenine dinucleotide (NAD) is a major electron carrier present in almost all living cells and creates gated potential by electron exchange from one chemical to another in terms of oxidation (NAD+) and reduction (NADH) reactions. NAD+ plays an important role directly or indirectly in protecting against various cardiovascular diseases, including heart failure, occlusion, ischemia-reperfusion (IR) injury, arrhythmia, myocardial infarction (MI), rhythmic disorder, and a higher order of cardiovascular complexity. Nicotinamide phosphoribosyl transferase (NAMPT) is well known as a rate-limiting enzyme in this pathway except for de-novo NAD synthesis and directly involved in the cardioprotective activity. There are two more enzymes - nicotinate phosphoribosyl transferase (NAPRT) and nicotinamide riboside kinase (NRK) - which also work as rate-limiting factors in the NAD+ synthesis pathway. This study concentrated on the role of NAMPT, NAPRT, and NRK in cardioprotective activity and prospective cardiac health.

Inhibitors of NAD+ Production in Cancer Treatment: State of the Art and Perspectives

The addiction of tumors to elevated nicotinamide adenine dinucleotide (NAD+) levels is a hallmark of cancer metabolism. Obstructing NAD+ biosynthesis in tumors is a new and promising antineoplastic strategy. Inhibitors developed against nicotinamide phosphoribosyltransferase (NAMPT), the main enzyme in NAD+ production from nicotinamide, elicited robust anticancer activity in preclinical models but not in patients, implying that other NAD+-biosynthetic pathways are also active in tumors and provide sufficient NAD+ amounts despite NAMPT obstruction. Recent studies show that NAD+ biosynthesis through the so-called "Preiss-Handler (PH) pathway", which utilizes nicotinate as a precursor, actively operates in many tumors and accounts for tumor resistance to NAMPT inhibitors. The PH pathway consists of three sequential enzymatic steps that are catalyzed by nicotinate phosphoribosyltransferase (NAPRT), nicotinamide mononucleotide adenylyltransferases (NMNATs), and NAD+ synthetase (NADSYN1). Here, we focus on these enzymes as emerging targets in cancer drug discovery, summarizing their reported inhibitors and describing their current or potential exploitation as anticancer agents. Finally, we also focus on additional NAD+-producing enzymes acting in alternative NAD+-producing routes that could also be relevant in tumors and thus become viable targets for drug discovery.

Targeting cancer stem cells as a strategy for reducing chemotherapy resistance in head and neck cancers

PURPOSE

Resistance to chemotherapy and radiotherapy is the primary cause of a poor prognosis in oncological patients. Researchers identified many possible mechanisms involved in gaining a therapy-resistant phenotype by cancer cells, including alterations in intracellular drug accumulation, detoxification, and enhanced DNA damage repair. All these features are characteristic of stem cells, making them the major culprit of chemoresistance. This paper reviews the most recent evidence regarding the association between the stemness phenotype and chemoresistance in head and neck cancers. It also investigates the impact of pharmacologically targeting cancer stem cell populations in this subset of malignancies.

METHODS

This narrative review was prepared based on the search of the PubMed database for relevant papers.

RESULTS

Head and neck cancer cells belonging to the stem cell population are distinguished by the high expression of certain surface proteins (e.g., CD10, CD44, CD133), pluripotency-related transcription factors (SOX2, OCT4, NANOG), and increased activity of aldehyde dehydrogenase (ALDH). Chemotherapy itself increases the percentage of stem-like cells. Importantly, the intratumor heterogeneity of stem cell subpopulations reflects cell plasticity which has great importance for chemoresistance induction.

CONCLUSIONS

Evidence points to the advantage of combining classical chemotherapeutics with stemness modulators thanks to the joint targeting of the bulk of proliferating tumor cells and chemoresistant cancer stem cells, which could cause recurrence.