Design, synthesis, and in vitro and in vivo biological studies of a 3'-deoxythymidine conjugate that potentially kills cancer cells selectively

Establishment of a murine hepatocellular carcinoma model by hydrodynamic injection and characterization of the immune tumor microenvironment

Hepatocellular carcinoma (HCC) is one of the most prevalent malignant neoplasms. Current treatments for HCC, such as tyrosine kinase inhibitors, have limited efficacy, highlighting the urgent need for better therapies. Immunotherapies, including anti-programmed death receptor 1 (PD-1) and anti-Cytotoxic T-lymphocyte associated protein 4 (CTLA-4), and more recently, the combination of anti-PD-L1 and anti-vascular endothelial growth factor (VEGF) monoclonal antibodies, have shown efficacy against HCC, resulting in Food and Drug Administration (FDA) approval. However, these immunotherapies only show efficiency in a small proportion of patients, meaning there is a great need to improve and optimize treatments against HCC. Accurate animal models that mimic human HCC are necessary to help better understand the nature of these tumors, which in turn will allow the development and testing of new treatments. Existing pre-clinical HCC models can be divided into non-genetic and genetic models. Non-genetic models involve implanting human or murine HCC cell lines or inducing tumors using chemical compounds or dietary modifications. These models have limitations, including slow tumor development and a lack of resemblance to human HCC. Genetic models, on the other hand, manipulate gene expression to induce HCC in mice and provide a better understanding of the effects of specific genes on tumor development. One method commonly used to generate HCC is hydrodynamic tail vein injection (HTVI), which consists of the delivery of oncogenes directly to the liver, resulting in expression and subsequent hepatocyte transformation. Usually, Sleeping Beauty transposase-containing plasmids are used to achieve stable and long-term gene expression. Once the HCC tumor is generated, and a proper tumor microenvironment (TME) is established, it is important to study the immune compartment of the TME, which plays a crucial role in HCC development and response to treatment. Techniques like flow cytometry can be used to analyze the immune cell populations in HCC tumors and assess their impact on tumor development and survival in mice. In this article, we thoroughly describe an example of the methodology to successfully generate HCC murine models via HTVI, and we propose a way to characterize the immune TME by flow cytometry.

Fabrication of Nanocrystals for Enhanced Distribution of a Fatty Acid Synthase Inhibitor (Orlistat) as a Promising Method to Relieve Solid Ehrlich Carcinoma-Induced Hepatic Damage in Mice

BACKGROUND

Orlistat (ORL) is an effective irreversible inhibitor of the lipase enzyme, and it possesses anticancer effects and limited aqueous solubility. This study was designed to improve the aqueous solubility, oral absorption, and tissue distribution of ORL via the formulation of nanocrystals (NCs).

METHODS

ORL-NC was prepared using the liquid antisolvent precipitation method (bottom-up technology), and it demonstrated significantly improved solubility compared with that of the blank crystals (ORL-BCs) and untreated ORL powder. The biodistribution and relative bioavailability of ORL-NC were investigated via the radiolabeling technique using Technetium-99m (99mTc). Female Swiss albino mice were used to examine the antitumor activity of ORL-NC against solid Ehrlich carcinoma (SEC)-induced hepatic damage in mice.

RESULTS

The prepared NCs improved ORL's solubility, bioavailability, and tissue distribution, with evidence of 258.70% relative bioavailability. In the in vivo study, the ORL-NC treatment caused a reduction in all tested liver functions (total and direct bilirubin, AST, ALT, and ALP) and improved modifications in liver sections that were marked using hematoxylin and eosin staining (H&E) and immunohistochemical staining (Ki-67 and ER-α) compared with untreated SEC mice.

CONCLUSIONS

The developed ORL-NC could be considered a promising formulation approach to enhance the oral absorption tissue distribution of ORL and suppress the liver damage caused by SEC.

In vitro naphthylquinoxaline thymidine conjugate and UVA treated cancer cells are effective therapeutic vaccines for tumors in vivo with CpG as the adjuvant

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Effective tumor immunotherapy with in vitro NAP-UVA treated cancer cells per se

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Marked survival improvement with CpG as the specific adjuvant

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Enhanced tumor specific and infiltrating active T cells by treatment vaccine

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Validated efficacy on established tumors with increased dosages

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Potential personalized immunotherapy applications

Introduction

Cancer cells induced into immunogenic cell death (ICD) in vitro can be directly used as a whole cell vaccine for tumor immunotherapy with many advantages, especially enacting immediate and intense ‘eat me’ signals to engage immune system. Unfortunately, there have been few successes with in vitro ICD cancer cells as a treatment vaccine.

Objective

To demonstrate that cancer cells treated in vitro with a new class of potent ICD inducer, naphthylquinoxaline thymidine conjugate (NAP) followed by UVA irradiation would be able to act as an effective tumor immunotherapy directly.

Methods

The therapeutic potentials of treated cancer cell plus different vaccine adjuvants were assessed by in vivo liver tumor model and in vitro mixed lymphocyte reaction studies. The elicited activated T cells were determined with immunohistochemistry and T cell induced cytotoxicity studies.

Results

Treatment of established H22 tumor with in vitro NAP and UVA treated cancer cell vaccine led to significantly improved survival. Further mixed lymphocyte reaction study implied that adjuvants alum and CpG would improve the therapeutic potential whereas poly IC would not be as effective. Subsequent in vivo validation of alum and CpG adjuvants indicated that only CpG in NAP and UVA treated cell vaccine resulted in markedly enhanced survival (median at 71 days and 50% tumor-free) as compared with PBS group (14.5 days, 0%) and CpG alone (36 days, 0%). It was revealed that the enhanced efficacy by CpG was specific to NAP and UVA treated cells. Moreover, the effective tumor immunotherapy was achieved through the infiltration of active CD4 and CD8 T cells in tumors and acquisition of cancer cell-specific cytotoxic CD8 T cells.

Conclusion

In vitro NAP and UVA treated cancer cells plus CpG adjuvant are effective tumor therapeutic vaccines per se.

Advance of structural modification of nucleosides scaffold

With Remdesivir being approved by FDA as a drug for the treatment of Corona Virus Disease 2019 (COVID-19), nucleoside drugs have once again received widespread attention in the medical community. Herein, we summarized modification of traditional nucleoside framework (sugar + base), traizole nucleosides, nucleoside analogues assembled by other drugs, macromolecule-modified nucleosides, and their bioactivity rules. 2′-“Ara”-substituted by –F or –CN group, and 3′-“ara” substituted by acetylenyl group can greatly influence their anti-tumor activities. Dideoxy dehydrogenation of 2′,3′-sites can enhance antiviral efficiencies. Acyclic nucleosides and L-type nucleosides mainly represented antiviral capabilities. 5-F Substituted uracil analogues exihibit anti-tumor effects, and the substrates substituted by –I, –CF₃, bromovinyl group usually show antiviral activities. The sugar coupled with 1-N of triazolid usually displays anti-tumor efficiencies, while the sugar coupled with 2-N of triazolid mainly represents antiviral activities. The nucleoside analogues assembled by cholesterol, polyethylene glycol, fatty acid and phospholipid would improve their bioavailabilities and bioactivities, or reduce their toxicities.

Antitumor and immunomodulatory effects of a novel multitarget inhibitor, CS2164, in mouse hepatocellular carcinoma models

As a novel orally active multitarget small molecule inhibitor, CS2164 has shown broad antitumor activities against several human tumor xenograft models in immune-compromised mice. However, the ability of CS2164 to modulate antitumor immunity in an immune-competent mouse tumor model remains undefined, although antiangiogenic treatment has been reported to affect immune cell infiltration and remodel the tumor immune microenvironment. In the present study, the subcutaneous and ascites hepatocellular carcinoma (HCC) models in syngeneic Balb/c mice established by inoculation of an H22 hepatoma cell line were utilized to investigate the antitumor and immunomodulatory effects of CS2164. Although the antitumor effects of CS2164 were validated in both subcutaneous and ascites HCC models in syngeneic mice, CS2164 treatment consistently modulated immune cell populations, both in the periphery and in tumor microenvironments, with upregulation of CD4⁺ and CD8⁺ T cells in the spleen, but downregulation of immunosuppressive populations including regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages in the spleen and tumor tissues. Furthermore, CS2164 increased the relative gene expression and protein production of several proinflammatory cytokines in tumor-related ascites. These results indicate that CS2164 exerts an antitumor effect associated with its immunomodulatory activities in mouse HCC models, and may also provide evidence for the immunotherapy potentiation of CS2164 in future cancer treatment.

Enhanced anticancer activity of combined treatment of imatinib and dipyridamole in solid Ehrlich carcinoma-bearing mice

The current study was designed to evaluate potential enhancement of the anticancer activity of imatinib mesylate (IM) with dipyridamole (DIP) and to investigate the underlying mechanisms of the combined therapy (IM/DIP) to reduce hepatotoxicity of IM in solid Ehrlich carcinoma (SEC)-bearing mice. SEC was induced in female albino mice as a model for experimentally induced breast cancer. Mice were randomly divided into seven groups (n = 10): SEC vehicle, IM₅₀ (50 mg/kg), IM₁₀₀ (100 mg/kg), DIP (35 mg/kg), a combination of IM₅₀/DIP and IM₁₀₀/DIP. On day 28th, mice were sacrificed and blood samples were collected for hematological studies. Biochemical determination of liver markers was evaluated. Glutamic oxaloacetic transaminase (SGOT), glutamic pyruvic transaminase (SGPT) and alkaline phosphatase (ALP) levels were assessed. In addition, MDR-1 gene expression and immunohistochemical staining of BAX and BCL-2 was done. Also, in vitro experiment for determination of IC50 of different treatments and combination index (CI) were assessed in both MCF-7 and HCT-116 cell lines. IM- and/or DIP-treated groups showed a significant reduction in tumor volume, weight, and serum levels of SGOT, SGPT, and AIP compared to vehicle group. In addition, reduction of VEGF, Ki67, and adenosine contents was also reported by treated groups. Also, IM/DIP combination showed lower IC50 than monotherapy. Combination index is less than 1 for IM/DIP combination in both cell lines. DIP as an adjuvant therapy potentiated the cytotoxic effect of IM, ameliorated its hepatic toxicity, and showed synergistic effect with IM in vitro cell lines. Furthermore, the resistance against IM therapy may be overcome by the use of DIP independent on mdr-1 gene expression.

Naphthyl quinoxaline thymidine conjugate is a potent anticancer agent post UVA activation and elicits marked inhibition of tumor growth through vaccination

Anticancer anthracyclines are cytotoxic drugs that can induce antitumor immune response as a secondary effect through immunogenic cell death (ICD) mechanism. However, the immunogenic potency is quite limited, possibly due to that these chemotherapeutic agents are not specifically developed as ICD inducers. Thus, new drug entities through studies focusing on enhanced ICD induction would significantly promote antitumor immune response in the vaccination application. We report here a naphthyl quinoxaline thymidine conjugate as a new class of cytotoxic compounds that effectively induced in vivo antitumor activity through the vaccination application. Synthesized naphthyl quinoxaline conjugates were weak fluorescent thymidine analog yet exhibited a pronounced anticancer activity in the low nanomolar range post UVA activation. The potent activity of naphthyl conjugate was able to induce the marked detection of ICD markers including ATP and HMGB1 extracellular and calreticulin intracellularly at 2 h post UVA activation. Most importantly, mice vaccinated with cells treated with naphthyl conjugate plus UVA exhibited complete tumor growth inhibition in the tumor challenge study, and the induced immunogenic inhibition was much more effective than that of mitoxantrone anthracycline drug. All these results demonstrate the high potential of naphthyl quinoxaline conjugate for the cancer cell vaccine against tumor.

Conjugates of Classical DNA/RNA Binder with Nucleobase: Chemical, Biochemical and Biomedical Applications

Among the most intensively studied classes of small molecules (molecular weight < 650) in biomedical research are small molecules that non-covalently bind to DNA/RNA, and another intensively studied class is nucleobase derivatives. Both classes have been intensively elaborated in many books and reviews. However, conjugates consisting of DNA/RNA binder covalently linked to nucleobase are much less studied and have not been reviewed in the last two decades. Therefore, this review summarized reports on the design of classical DNA/RNA binder - nucleobase conjugates, as well as data about their interactions with various DNA or RNA targets, and even in some cases protein targets are involved. According to these data, the most important structural aspects of selective or even specific recognition between small molecule and target are proposed, and where possible related biochemical and biomedical aspects were discussed. The general conclusion is that this, rather new class of molecules showed an amazing set of recognition tools for numerous DNA or RNA targets in the last two decades, as well as few intriguing in vitro and in vivo selectivities. Several lead research lines show promising advancements toward either novel, highly selective markers or bioactive, potentially druggable molecules.

Nucleic Acid Bioconjugates in Cancer Detection and Therapy

Nucleoside- and nucleotide-based chemotherapeutics have been used to treat cancer for more than 50 years. However, their inherent cytotoxicities and the emergent resistance of tumors against treatment has inspired a new wave of compounds in which the overall pharmacological profile of the bioactive nucleic acid component is improved by conjugation with delivery vectors, small-molecule drugs, and/or imaging modalities. In this manner, nucleic acid bioconjugates have the potential for targeting and effecting multiple biological processes in tumors, leading to synergistic antitumor effects. Consequently, tumor resistance and recurrence is mitigated, leading to more effective forms of cancer therapy. Bioorthogonal chemistry has led to the development of new nucleoside bioconjugates, which have served to improve treatment efficacy en route towards FDA approval. Similarly, oligonucleotide bioconjugates have shown encouraging preclinical and clinical results. The modified oligonucleotides and their pharmaceutically active formulations have addressed many weaknesses of oligonucleotide-based drugs. They have also paved the way for important advancements in cancer diagnosis and treatment. Cancer-targeting ligands such as small-molecules, peptides, and monoclonal antibody fragments have all been successfully applied in oligonucleotide bioconjugation and have shown promising anticancer effects in vitro and in vivo. Thus, the application of bioorthogonal chemistry will, in all likelihood, continue to supply a promising pipeline of nucleic acid bioconjugates for applications in cancer detection and therapy.

Structure-activity relationship study of anticancer thymidine-quinoxaline conjugates under the low radiance of long wavelength ultraviolet light for photodynamic therapy

Thymidine quinoxaline conjugate (dT-QX) is a thymidine analog with selective cytotoxicity against different cancer cells. In this study, the structure activity relationship study of dT-QX analogs was carried out under the low radiance of black fluorescent (UVA-1) light. Significantly enhanced cytotoxicity was observed under UVA-1 activation among analogs containing both thymidine and quinoxaline moieties with different length of the linker, stereochemical configuration and halogenated substituents. Among these analogs, the thymidine dichloroquinoxaline conjugate exhibited potent activity under UVA-1 activation as the best candidate with EC50 at 0.67 μM and 1.3 μM against liver and pancreatic cancer cells, respectively. In contrast, the replacement of thymidine moiety with a galactosyl residue or the replacement of quinoxaline moiety with a fluorescent pyrenyl residue or a simplified diketone structure resulted in the full loss of activity. Furthermore, it was revealed that the low radiance of UVA-1 at 3 mW/cm(2) for 20 min was sufficient enough to induce the full cytotoxicity of thymidine dichloroquinoxaline conjugate and that the cytotoxic mechanism was achieved through a rapid and steady production of reactive oxygen species.

Anticancer activity of a thymidine quinoxaline conjugate is modulated by cytosolic thymidine pathways

BACKGROUND

High levels of thymidine kinase 1 (TK1) and thymidine phosphorylase (TYMP) are key molecular targets by thymidine therapeutics in cancer treatment. The dual roles of TYMP as a tumor growth factor and a key activation enzyme of anticancer metabolites resulted in a mixed outcome in cancer patients. In this study, we investigated the roles of TK1 and TYMP on a thymidine quinoxaline conjugate to evaluate an alternative to circumvent the contradictive role of TYMP.

METHODS

TK1 and TYMP levels in multiple liver cell lines were assessed along with the cytotoxicity of the thymidine conjugate. Cellular accumulation of the thymidine conjugate was determined with organelle-specific dyes. The impacts of TK1 and TYMP were evaluated with siRNA/shRNA suppression and pseudoviral overexpression. Immunohistochemical analysis was performed on both normal and tumor tissues. In vivo study was carried out with a subcutaneous liver tumor model.

RESULTS

We found that the thymidine conjugate had varied activities in liver cancer cells with different levels of TK1 and TYMP. The conjugate mainly accumulated at endothelial reticulum and was consistent with cytosolic pathways. TK1 was responsible for the cytotoxicity yet high levels of TYMP counteracted such activities. Levels of TYMP and TK1 in the liver tumor tissues were significantly higher than those of normal liver tissues. Induced TK1 overexpression decreased the selectivity of dT-QX due to the concurring cytotoxicity in normal cells. In contrast, shRNA suppression of TYMP significantly enhanced the selective of the conjugate in vitro and reduced the tumor growth in vivo.

CONCLUSIONS

TK1 was responsible for anticancer activity of dT-QX while levels of TYMP counteracted such an activity. The counteraction by TYMP could be overcome with RNA silencing to significantly enhance the dT-QX selectivity in cancer cells.

Cyanine 5.5 conjugated nanobubbles as a tumor selective contrast agent for dual ultrasound-fluorescence imaging in a mouse model

Nanobubbles and microbubbles are non-invasive ultrasound imaging contrast agents that may potentially enhance diagnosis of tumors. However, to date, both nanobubbles and microbubbles display poor in vivo tumor-selectivity over non-targeted organs such as liver. We report here cyanine 5.5 conjugated nanobubbles (cy5.5-nanobubbles) of a biocompatible chitosan-vitamin C lipid system as a dual ultrasound-fluorescence contrast agent that achieved tumor-selective imaging in a mouse tumor model. Cy5.5-nanobubble suspension contained single bubble spheres and clusters of bubble spheres with the size ranging between 400-800 nm. In the in vivo mouse study, enhancement of ultrasound signals at tumor site was found to persist over 2 h while tumor-selective fluorescence emission was persistently observed over 24 h with intravenous injection of cy5.5-nanobubbles. In vitro cell study indicated that cy5.5-flurescence dye was able to accumulate in cancer cells due to the unique conjugated nanobubble structure. Further in vivo fluorescence study suggested that cy5.5-nanobubbles were mainly located at tumor site and in the bladder of mice. Subsequent analysis confirmed that accumulation of high fluorescence was present at the intact subcutaneous tumor site and in isolated tumor tissue but not in liver tissue post intravenous injection of cy5.5-nanobubbles. All these results led to the conclusion that cy5.5-nanobubbles with unique crosslinked chitosan-vitamin C lipid system have achieved tumor-selective imaging in vivo.