NO• and Pancreatic Cancer: A Complex Interaction with Therapeutic Potential

Strategies for drug targeting in pancreatic cancer

BACKGROUND

Pancreatic cancer is expected to replace lung cancer as the second greatest cause of cancer mortality by 2025. It has been a particularly the most lethal kind of cancer.

OBJECTIVE

Despite the new innovations, research, and improvements in drug design; there are many hurdles limiting their therapeutic applications such as intrinsic resistance to chemotherapeutics, inability to deliver a sufficient concentration of drug to the target site, lack of effectiveness of drug delivery systems. These are the major contributing factors to limit the treatment. So, the main objective is to overcome these types of problems by nanotechnology and ligand conjugation approach to achieve targeted drug delivery.

METHOD

Nanotechnology has emerged as a major approach to develop cancer treatment. Regardless of the severity, there are several issues that restrict the therapeutic impact, including inadequate transport across biological barriers, limited cellular absorption, degradation, and faster clearance.

RESULT

Targeted drug delivery may overcome these obstacles by binding a natural ligand to the surface of nanocarriers, which enhances the drug's capacity to release at the desired site and minimizes adverse effects.

CONCLUSION

This study will investigate the possible outcomes of targeted therapeutic agent delivery in the treatment of pancreatic cancer, as well as the limitations and future prospects.

Therapeutic Influence on Important Targets Associated with Chronic Inflammation and Oxidative Stress in Cancer Treatment

Chronic inflammation and oxidative stress are the interconnected pathological processes, which lead to cancer initiation and progression. The growing level of oxidative and inflammatory damage was shown to increase cancer severity and contribute to tumor spread. The overproduction of reactive oxygen species (ROS), which is associated with the reduced capacity of the endogenous cell defense mechanisms and/or metabolic imbalance, is the main contributor to oxidative stress. An abnormal level of ROS was defined as a predisposing factor for the cell transformation that could trigger pro-oncogenic signaling pathways, induce changes in gene expression, and facilitate accumulation of mutations, DNA damage, and genomic instability. Additionally, the activation of transcription factors caused by a prolonged oxidative stress, including NF-κB, p53, HIF1α, etc., leads to the expression of several genes responsible for inflammation. The resulting hyperactivation of inflammatory mediators, including TNFα, TGF-β, interleukins, and prostaglandins can contribute to the development of neoplasia. Pro-inflammatory cytokines were shown to trigger adaptive reactions and the acquisition of resistance by tumor cells to apoptosis, while promoting proliferation, invasion, and angiogenesis. Moreover, the chronic inflammatory response leads to the excessive production of free radicals, which further aggravate the initiated reactions. This review summarizes the recent data and progress in the discovery of mechanisms that associate oxidative stress and chronic inflammation with cancer onset and metastasis. In addition, the review provides insights for the development of therapeutic approaches and the discovery of natural substances that will be able to simultaneously inhibit several key oncological and inflammation-related targets.

New possible silver lining for pancreatic cancer therapy: Hydrogen sulfide and its donors

As one of the most lethal diseases, pancreatic cancer shows a dismal overall prognosis and high resistance to most treatment modalities. Furthermore, pancreatic cancer escapes early detection during the curable period because early symptoms rarely emerge and specific markers for this disease have not been found. Although combinations of new drugs, multimodal therapies, and adjuvants prolong survival, most patients still relapse after surgery and eventually die. Consequently, the search for more effective treatments for pancreatic cancer is highly relevant and justified. As a newly re-discovered mediator of gasotransmission, hydrogen sulfide (H₂S) undertakes essential functions, encompassing various signaling complexes that occupy key processes in human biology. Accumulating evidence indicates that H₂S exhibits bimodal modulation of cancer development. Thus, endogenous or low levels of exogenous H₂S are thought to promote cancer, whereas high doses of exogenous H₂S suppress tumor proliferation. Similarly, inhibition of endogenous H₂S production also suppresses tumor proliferation. Accordingly, H₂S biosynthesis inhibitors and H₂S supplementation (H₂S donors) are two distinct strategies for the treatment of cancer. Unfortunately, modulation of endogenous H₂S on pancreatic cancer has not been studied so far. However, H₂S donors and their derivatives have been extensively studied as potential therapeutic agents for pancreatic cancer therapy by inhibiting cell proliferation, inducing apoptosis, arresting cell cycle, and suppressing invasion and migration through exploiting multiple signaling pathways. As far as we know, there is no review of the effects of H₂S donors on pancreatic cancer. Based on these concerns, the therapeutic effects of some H₂S donors and NO–H₂S dual donors on pancreatic cancer were summarized in this paper. Exogenous H₂S donors may be promising compounds for pancreatic cancer treatment.

NO• /RUNX3/kynurenine metabolic signaling enhances disease aggressiveness in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy and is refractory to available treatments. Delineating the regulatory mechanisms of metabolic reprogramming, a key event in pancreatic cancer progression, may identify candidate targets with potential therapeutic significance. We hypothesized that inflammatory signaling pathways regulate metabolic adaptations in pancreatic cancer. Metabolic profiling of tumors from PDAC patients with a high- (>median, n = 31) and low-NOS2 (inducible nitric oxide synthase; <median, n = 32) mRNA expression was performed. Differentially abundant metabolites were analyzed and linked with patient survival. The functional role of the prognostically significant metabolite and the mechanism of its regulation by NOS2/NO^• (nitric oxide)-mediated signaling pathway was elucidated. The level of kynurenine, a tryptophan metabolite, was associated with high NOS2 expression, and a higher level of kynurenine predicted poor survival in patients (n = 63, p = 0.01). Gene expression analysis in PDAC tumors (n = 63) showed a positive correlation between the expression of NOS2 and the tryptophan/kynurenine pathway genes, including indoleamine-2,3-dioxygenase 1 (IDO1) and several aryl hydrocarbon receptor (AHR)-target genes including NFE2L2 (NRF2), SERPINB2, IL1b, IL6 and IL8, which are implicated in pancreatic cancer. Consistently, treatment of pancreatic cancer cell lines with NO^• donor induced IDO1, kynurenine production and the expression of AHR-target genes. Furthermore, kynurenine treatment enhanced spheroid growth and invasive potential of pancreatic cancer cell lines. Mechanistically, NO^• -induced IDO1/Kynurenine/AHR signaling was mediated by RUNX3 transcription factor. Our findings identified a novel NO^• /RUNX3/Kynurenine metabolic axis, which enhances disease aggressiveness in pancreatic cancer and may have potential translational significance in improving disease outcome.

Gaseous signaling molecules and their application in resistant cancer treatment: from invisible to visible

Multidrug resistance (MDR) in cancer remains a critical obstacle for efficient chemotherapy. Many MDR reversal agents have been discovered but failed in clinical trials due to severe toxic effects. Gaseous signaling molecules (GSMs), such as oxygen, nitric oxide, hydrogen sulfide and carbon monoxide, play key roles in regulating cell biological function and MDR. Compared with other toxic chemosensitizing agents, GSMs are endogenous and biocompatible molecules with little side effects. Research show that GSM modulators, including pharmaceutical formulations of GSMs (combined with conventional chemotherapeutic drugs) and GSM-donors (small molecules with GSMs releasing property), can overcome or reverse MDR. This review discusses the roles of these four GSMs in modulating MDR, and summarizes GSMs modulators in treating cancers with drug resistance.