Potentiation of the cytostatic effect of melphalan on colorectal cancer hepatic metastases by infusion of buthionine sulfoximine (BSO) in the rat: enhanced tumor glutathione depletion by infusion of BSO in the hepatic artery

Buthionine sulfoximine and chemoresistance in cancer treatments: a systematic review with meta-analysis of preclinical studies

Buthionine sulfoximine (BSO) is a synthetic amino acid that blocks the biosynthesis of reduced glutathione (GSH), an endogenous antioxidant cellular component present in tumor cells. GSH levels have been associated with tumor cell resistance to chemotherapeutic drugs and platinum compounds. Consequently, by depleting GSH, BSO enhances the cytotoxicity of chemotherapeutic agents in drug-resistant tumors. Therefore, the aim of this study was to conduct a systematic review with meta-analysis of preclinical studies utilizing BSO in cancer treatments. The systematic search was carried out using the following databases: PubMed, Web of Science, Scopus, and EMBASE up until March 20, 2023, in order to collect preclinical studies that evaluated BSO, alone or in association, as a strategy for antineoplastic therapy. One hundred nine investigations were found to assess the cytotoxic potential of BSO alone or in combination with other compounds. Twenty-one of these met the criteria for performing the meta-analysis. The evidence gathered indicated that BSO alone exhibits cytotoxic activity. However, this compound is generally used in combination with other antineoplastic strategies, mainly chemotherapy ones, to improve cytotoxicity to carcinogenic cells and treatment efficacy. Finally, this review provides important considerations regarding BSO use in cancer treatment conditions, which might optimize future studies as a potential adjuvant antineoplastic therapeutic tool.

Molecular Basis of the Antiangiogenic Action of Rosmarinic Acid, a Natural Compound Targeting Fibroblast Growth Factor-2/FGFR Interactions

Fibroblast growth factor (FGF2)/fibroblast growth factor receptor (FGFR) signalling plays a major role both in physiology and in several pathologies, including cancer development, metastasis formation and resistance to therapy. The development of small molecules, acting extracellularly to target FGF2/FGFR interactions, has the advantage of limiting the adverse effects associated with current intracellular FGFR inhibitors. Herein, we discuss the ability of the natural compound rosmarinic acid (RA) to induce FGF2/FGFR complex dissociation. The molecular-level description of the FGF2/FGFR/RA system, by NMR spectroscopy and docking, clearly demonstrates that RA binds to the FGFR-D2 domain and directly competes with FGF2 for the same binding site. Direct and allosteric perturbations combine to destabilise the complex. The proposed molecular mechanism is validated by cellular studies showing that RA inhibits FGF2-induced endothelial cell proliferation and FGFR activation. Our results can serve as the basis for the development of new extracellular inhibitors of the FGF/FGFR pathways.

Functionalized N-Pyridinylmethyl Engrafted Bisarylmethylidenepyridinones as Anticancer Agents

Structurally interesting N-pyridinylmethyl engrafted bisarylmethylidenepyridinones with high functionality have been constructed in good yield. The structural interpretation of these compounds has been done with the aid of spectroscopic analysis and further established by single crystal X-ray diffraction studies. Following physical characterization, the synthesized compounds were tested for their in vitro anticancer activity against HepG2 cancer cells and it was found that all of the compounds exhibited some level of activity. We observed a significant level of cell viability losses to the cancer cells, while only smaller losses to the non-cancer cells were observed. Besides, the mechanistic investigation of toxicology revealed that the cancer cells were undergoing apoptotic pathway, induced by the generation of oxidative stress and the involvement of caspases. The analysis provides preliminary evidence for the successful control of cancer cells with a minimal effect on healthy normal cells because of the high IC50 levels and cell death mechanisms.

Preclinical evaluation of azathioprine plus buthionine sulfoximine in the treatment of human hepatocarcinoma and colon carcinoma

AIM: To evaluate the efficacy and the safety of azathioprine (AZA) and buthionine sulfoximine (BSO) by localized application into HepG2 tumor in vivo.

METHODS: Different hepatoma and colon carcinoma cell lines (HepG2, HuH7, Chang liver, LoVo, RKO, SW-48, SW-480) were grown in minimal essencial medium supplemented with 10% fetal bovine serum and 1% antibiotic/antimycotic solution and maintained in a humidified 37 °C incubator with 5% CO₂. These cells were pretreated with BSO for 24 h and then with AZA for different times. We examined the effects of this combination on some proteins and on cellular death. We also studied the efficacy and the safety of AZA (6 mg/kg per day) and BSO (90 mg/kg per day) in HepG2 tumor growth in vivo using athymic mice. We measured safety by serological markers such as aminotransferases and creatine kinase.

RESULTS: The in vitro studies revealed a new mechanism of action for the AZA plus BSO combination in the cancer cells compared with other thiopurines (6-mercaptopurine, 6-methylmercaptopurine, 6-thioguanine and 6-methylthioguanine) in combination with BSO. The cytotoxic effect of AZA plus BSO in HepG2 cells resulted from necroptosis induction in a mitochondrial-dependent manner. From kinetic studies we suggest that glutathione (GSH) depletion stimulates c-Jun amino-terminal kinase and Bax translocation in HepG2 cells with subsequent deregulation of mitochondria (cytochrome c release, loss of membrane potential), and proteolysis activation leading to loss of membrane integrity, release of lactate dehydrogenase and DNA degradation. Some of this biochemical and cellular changes could be reversed by N-acetylcysteine (a GSH replenisher). In vivo studies showed that HepG2 tumor growth was inhibited when AZA was combined with BSO.

CONCLUSION: Our studies suggest that a combination of AZA plus BSO could be useful for localized treatment of hepatocellular carcinoma as in the currently used transarterial chemoembolization method.

Near-infrared fluorescence imaging of liver metastases in rats using indocyanine green

BACKGROUND

Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) is a promising technique to obtain real-time assessment of the extent and number of colorectal liver metastases during surgery. The current study aims to optimize dosage and timing of ICG administration.

MATERIALS AND METHODS

Liver tumors were induced in 18 male WAG/Rij rats by subcapsular inoculation of CC531 rat colorectal cancer cells into three distinct liver lobes. Rats were divided in two groups: imaging after 24 and 48 h or 72 and 96 h after intravenous ICG administration. In each time group, rats were allocated to three dose groups: 0.04, 0.08, or 0.16 mg ICG. Intraoperative imaging and ex vivo measurements were performed using the Mini-FLARE imaging system and confirmed by fluorescence microscopy. Fluorescence intensity was quantified using the Mini-FLARE software and the difference between tumor signal and liver signal (tumor-to-liver ratio; TLR) was calculated.

RESULTS

In all 18 rats, all colorectal liver metastases (n = 34), some as small as 1.2 mm, were identified using ICG and the Mini-FLARE imaging system. Average tumor-to-liver ratio (TLR) over all groups was 3.0 ± 1.2. TLR was significantly higher in the 72 h time group compared with other time points. ICG dose did not significantly influence TLR, but a trend was found favoring the 0.08 mg dose group. Fluorescence microscopy demonstrated a clear fluorescent rim around the tumor.

CONCLUSIONS

This study demonstrates that colorectal cancer liver metastases can be clearly identified during surgery using ICG and the Mini-FLARE imaging system, with optimal timing of 72 h post-injection and an optimal dose of 0.08 mg (0.25 mg/kg) ICG. NIR fluorescence imaging has the potential to improve intraoperative detection of micrometastases and, thus, the completeness of resection.

Transient alteration of cellular redox buffering before irradiation triggers apoptosis in head and neck carcinoma stem and non-stem cells

Background

Head and neck squamous cell carcinoma (HNSCC) is an aggressive and recurrent malignancy owing to intrinsic radioresistance and lack of induction of apoptosis. The major focus of this work was to design a transient glutathione depleting strategy during the course of irradiation of HNSCC in order to overcome their radioresistance associated with redox adaptation.

Methodology/Principal Findings

Treatment of SQ20B cells with dimethylfumarate (DMF), a GSH-depleting agent, and L-Buthionine sulfoximine (BSO), an inhibitor of GSH biosynthesis 4 h before a 10 Gy irradiation led to the lowering of the endogenous GSH content to less than 10% of that in control cells and to the triggering of radiation-induced apoptotic cell death. The sequence of biochemical events after GSH depletion and irradiation included ASK-1 followed by JNK activation which resulted in the triggering of the intrinsic apoptotic pathway through Bax translocation to mitochondria.

Conclusions

This transient GSH depletion also triggered radiation-induced cell death in SQ20B stem cells, a key event to overcome locoregional recurrence of HNSCC. Finally, our in vivo data highlight the relevance for further clinical trials of endogenous redox modulation to enhance the cytotoxic effects of radiotherapy.

Intraoperative near-infrared fluorescence imaging of colorectal metastases targeting integrin α(v)β(3) expression in a syngeneic rat model

AIM

Near-infrared (NIR) fluorescence optical imaging is a promising technique to assess the extent of colorectal metastases during curative-intended surgery. However, NIR fluorescence imaging of liver metastases is highly challenging due to hepatic uptake and clearance of many fluorescent dyes. In the current study, the biodistribution and the ability to demarcate liver and peritoneal metastases were assessed during surgery in a syngeneic rat model of colorectal cancer using an integrin α(v)β(3)-directed NIR fluorescence probe.

METHODS

Liver tumors and peritoneal metastases were induced in 7 male WAG/Rij rats by subcapsular inoculation of 0.5 × 10(6) CC531 colorectal cancer rat cells into three distinct liver lobes. Intraoperative and ex vivo fluorescence measurements were performed 24 (N = 3 rats, 7 tumors) and 48 h (N = 4 rats, 9 tumors) after intravenous administration of the integrin α(v)β(3)-directed NIR fluorescence probe.

RESULTS

Colorectal metastases had a minimal two-fold higher NIR fluorescence signal than healthy liver tissue and other abdominal organs (p < 0.001). The tumor-to-background ratio was independent of time of imaging (24 h vs. 48 h post-injection; p = 0.31), which facilitates flexible operation planning in future clinical applications. Total fluorescence intensity was significantly correlated with the size of metastases (R(2) = 0.92 for the 24 h group, R(2) = 0.96 for the 48 h group).

CONCLUSION

These results demonstrate that colorectal intra-abdominal metastases can be clearly demarcated during surgery using an integrin α(v)β(3) targeting NIR fluorescence probe. Translating these findings to the clinic will have an excellent potential to substantially improve the quality of cancer surgery.

Potential role of N-myristoyltransferase in cancer

Colorectal cancer is the second leading cause of malignant death, and better preventive strategies are needed. The treatment of colonic cancer remains difficult because of the lack of effective chemotherapeutic agents; therefore it is important to continue to search for cellular functions that can be disrupted by chemotherapeutic drugs resulting in the inhibition of the development and progression of cancer. The current knowledge of the modification of proteins by myristoylation involving myristoyl-CoA: protein N-myristoyltransferase (NMT) is in its infancy. This process is involved in the pathogenesis of cancer. We have reported for the first time that NMT activity and protein expression were higher in human colorectal cancer, gallbladder carcinoma and brain tumors. In addition, an increase in NMT activity appeared at an early stage in colonic carcinogenesis. It is conceivable therefore that NMT can be used as a potential marker for the early detection of cancer. These observations lead to the possibility of developing NMT specific inhibitors, which may be therapeutically useful. We proposed that HSC70 and/or enolase could be used as an anticancer therapeutic target. This review summarized the status of NMT in cancer which has been carried in our laboratory.

In children and adolescents, the pharmacodynamics of high-dose busulfan is dependent on the second alkylating agent used in the combined regimen (melphalan or thiotepa)

A strong relationship has been demonstrated between high systemic exposure to busulfan and the occurrence of hepatic veno-occlusive disease (HVOD) after a busulfan-cyclophosphamide regimen (BU CY). We report a prospective study aimed at exploring the pharmacodynamics of high-dose busulfan combined with either melphalan (BU MEL) or thiotepa (BU TTP) followed by autologous stem cell transplantation in children and adolescents with a malignant solid tumor. Busulfan was given orally at a total dose of 600 mg m(-2). In all, 45 patients with a median age of 6.3 years were included in the study: 25 received BU MEL and 20 received BU TTP. The incidence of HVOD was 44% (CI 95% [23-65%]) in the BU MEL group and 25% (CI95% [9-49%]) in the BU TTP group. In the BU TTP group, patients who developed HVOD had a significantly higher AUC 0-6 h after the 13th dose (6201+/-607 h ng ml(-1)) than those who did not (5024+/-978 h ng ml(-1)) (P<0.05). In the BU MEL group, there was no difference in terms of systemic exposure to busulfan between patients who developed HVOD and those who did not. In conclusion, the guidelines established for monitoring BU CY cannot be extrapolated when busulfan is combined with another drug.

Cytotoxic 1,4-bis(2-oxo-1-cycloalkylmethylene)benzenes and related compounds

A series of 1,4-bis(2-oxo-1-cycloalkylmethylene)benzenes 2a-c and 4 and a related acyclic analogue 6a were synthesised and converted to the corresponding Mannich bases 3a-c, 5 and 6b. Evaluation of these compounds against murine P388 and L1210 cells as well as human Molt 4/C8 and CEM T-lymphocytes revealed that the Mannich bases were more cytotoxic than the corresponding unsaturated ketones. 1,4-bis(3-Dimethylaminomethyl-2-oxo-1-cyclohexylmethylene)benzene dihydrochloride (3a) had lower IC(50) values than melphalan against the four cell lines and was 15 times more potent than this drug when examined against a panel of human tumours.

Development of resistance to glutathione depletion-induced cell death in CC531 colon carcinoma cells: association with increased expression of bcl-2

The glutathione (GSH) level of CC531 rat colorectal cancer cells is readily decreased by exposure to buthionine sulfoximine (BSO), an inhibitor of GSH synthesis; at 25 microM BSO, these cells died in a non-apoptotic fashion. By continuous exposure of CC531 cells to increasing concentrations of BSO, we obtained a BSO-resistant cell line (CCBR25) that was 50 times more resistant to BSO than the parental cell line. Whereas the GSH content of CCBR25 and CC531 cells was similar, the former contained a much higher level of the Bcl-2 protein. After stable transfection of CC531 cells with the human bcl-2 gene, the resulting Bcl-2-overexpressing cell line appeared to be 9 times more resistant to BSO than the parental cell line. These findings suggest that the Bcl-2 protein offers resistance against the cytotoxic effect of severe GSH depletion.