Cell-Derived Allograft Models as a Solution to the Obstacles of Preclinical Studies under Limited Resources: A Systematic Review on Experimental Lung Cancer Animal Models

BACKGROUND

The use of appropriate animal models for cancer studies is a major challenge, particularly for investigators who lack the resources to maintain and use xenograft animals or genetically engineered mouse models (GEMM). In addition, several countries intending to incorporate these models must conduct importation procedures, posing an additional challenge.

OBJECTIVE

This review aimed to explore the use of cell-derived allograft or syngeneic models under limited resources. The results can be used by investigators, specifically from low-middle-income countries, to contribute to lung cancer eradication.

METHOD

A literature search was carried out on various databases, including PubMed, Web of Science, and Scopus. In addition, the publication year of the selected articles was set between 2013 and 2023 with different search components (SC), namely lung cancer (SC1), animal models (SC2), and preclinical studies (SC3).

RESULTS

This systematic review focused on selecting animals, cells, and methods that could be applied to generating allograft-type lung cancer animal models from 101 included articles.

CONCLUSION

Based on the results, the use of cell-derived allograft models in cancer studies is feasible and relevant, and it provides valuable insights regarding the conditions with limited resources.

Translocator Protein 18 kDa (TSPO): A Promising Molecular Target for Image-Guided Surgery of Solid Cancers

The translocator protein 18-kDa (TSPO) is a mitochondrial membrane protein that is previously identified as the peripheral benzodiazepine receptor (PBR). Furthermore, it plays a significant role in a diverse range of biochemical processes, including steroidogenesis, mitochondrial cholesterol transport, cell survival and death, cell proliferation, and carcinogenesis. Several investigations also reported its roles in various types of cancers, including colorectal, brain, breast, prostate, and lung cancers, as well as melanoma. According to a previous study, the expression of TSPO was upregulated in cancer cells, which corresponds to an aggressive phenotype and/or poor prognosis. Consequently, the potential for crafting diagnostic and prognostic tools with a focus on TSPO holds great potential. In this context, several radioligands designed to target this protein have been identified, and some of the candidates have advanced to clinical trials. In recent years, the use of hybrid probes with radioactive and fluorescence molecules for image-guided surgery has exhibited promising results in animal and human studies. This indicates that the approach can serve as a valuable surgical navigator during cancer surgery. The current hybrid probes are built from various molecular platforms, including small molecules, nanoparticles, and antibodies. Although several TSPO-targeted imaging probes have been developed, their development for image-guided surgery of cancers is still limited. Therefore, this review aims to highlight recent findings on the involvement of TSPO in carcinogenesis, as well as provide a new perspective on the potential application of TSPO-targeted hybrid probes for image-guided surgery.

New hybrid radio-fluorescent probes [131I]-BPF-01 and [131I]-BPF-02 for visualisation of cancer cells: Synthesis and preliminary in vitro and ex vivo evaluations

We synthesised and biologically evaluated two new hybrid probes [131I]BPF-01 and [131I]BPF-02 which were built from three structural entities: benzothiazole-phenyl, fluorescein isothiocyanate (FITC), and iodine-131. These probes were designed for potential applications in assisting surgical procedures of solid cancers. The cytotoxicity study demonstrated that fluorescent probes BPF-01 (31.23 μg/mL) and BPF-02 (250 μg/mL) were relatively not toxic to normal immortalized human keratinocytes (HaCaT) cells, as indicated by the percentage of cell survival above 50 %. Furthermore, both probes displayed low to moderate anticancer activity against the breast cancer cells (MDA-MB-231) and prostate cancer cells (LNCaP and DU-145). The probe BPF-01 apparently showed an accumulation in the tumour tissues, as suggested by ex vivo fluorescence examinations. In addition, the cellular uptake study suggests that hybrid probe [131I]-BPF-01 was potentially accumulated in the MCF-7 cell line with the highest uptake of 16.11 ± 1.52 % after 2 h of incubation, approximately 50-fold higher than the accumulation of iodine-131 (control). The magnetic bead assay suggests that [131I]-BPF-02 and [131I]-BPF-02 showed a promising capability to interact with translocator protein 18 kDa (TSPO). Moreover, the computational data showed that the binding scores for ligands 7-8, BPF-01 and BPF-02, and [131I]-BPF-01 and [131I]-BPF-02 in the TSPO were considerably high. Accordingly, fluorescent probes BPF-01 and BPF-02, and hybrid probes [131I]BPF-01 and [131I]BPF-02 can be further developed for targeting cancer cells during intraoperative tumour surgery.

Synthesis and Biological Evaluation of New Fluorescent Probe BPN-01: A Model Molecule for Fluorescence Image-guided Surgery

Fluorescence image-guided surgery (FIGS) can serve as a tool to achieve successful resection of tumour tissues during surgery, serving as a surgical navigator for surgeons. FIGS relies on the use of fluorescent molecules that can specifically interact with cancer cells. In this work, we developed a new model of fluorescent probe based on benzothiazole-phenylamide moiety featuring the visible fluorophore nitrobenzoxadiazole (NBD), namely BPN-01. This compound was designed and synthesised for potential applications in the tissue biopsy examination and ex-vivo imaging during FIGS of solid cancers. The probe BPN-01 exhibited favourable spectroscopic properties, particularly in nonpolar and alkaline solvents. Moreover, in vitro fluorescence imaging revealed that the probe appeared to recognise and be internalised in the prostate (DU-145) and melanoma (B16-F10) cancer cells, but not in the normal cells (myoblast C2C12). The cytotoxicity studies revealed that probe BPN-01 was not toxic to the B16 cells, suggesting excellent biocompatibility. Furthermore, the computational analysis showed that the calculated binding affinity of the probe to both translocator protein 18 kDa (TSPO) and human epidermal growth factor receptor 2 (HER2) was considerably high. Hence, probe BPN-01 displays promising properties and may be valuable for visualising cancer cells in vitro. Furthermore, ligand 5 can potentially be labelled with NIR fluorophore and radionuclide, and serves as a dual imaging agent for in vivo applications.

Radiosynthesis, Stability, Lipophilicity, and Cellular Uptake Evaluations of [131I]Iodine-α-Mangostin for Breast Cancer Diagnosis and Therapy

The high rate of incidence and mortality caused by breast cancer encourage urgent research to immediately develop new diagnostic and therapeutic agents for breast cancer. Alpha mangostin (AM) is a natural compound reported to have anti-breast cancer properties. Its electron-donating groups structure allows it to be labeled with an iodine-131 radioisotope to develop a candidate of a diagnostic and therapeutic agent for breast cancer. This study aims to prepare the [^131I]Iodine-α-mangostin ([¹³¹I]I-AM) and evaluate its stability, lipophilicity, and cellular uptake in breast cancer cell lines. The [¹³¹I]I-AM was prepared by direct radiosynthesis with Chloramine-T method in two conditions (A: AM dissolved in NaOH, B: AM dissolved in ethanol). Reaction time, pH, and mass of the oxidizing agent were optimized as crucial parameters that affected the radiosynthesis reaction. Further analysis was conducted using the radiosynthesis conditions with the highest radiochemical purity (RCP). Stability tests were carried out at three storage conditions, including -20, 2, and 25 °C. A cellular uptake study was performed in T47D (breast cancer cell line) and Vero cells (noncancerous cell line) at various incubation times. The results show that the RCP values of [¹³¹I]I-AM under conditions A and B were 90.63 ± 0.44 and 95.17 ± 0.80% (n = 3), respectively. In the stability test, [¹³¹I]I-AM has an RCP above 90% after three days of storage at -20 °C. A significant difference was obtained between [¹³¹I]I-AM uptake in T47D and Vero cells. Based on these results, [¹³¹I]I-AM has been prepared with high RCP, stable at -20 °C, and specifically uptaken by breast cancer cell lines. Biodistribution evaluations in animals are recommended as further research in developing [¹³¹I]I-AM as a diagnostic and therapeutic agent for breast cancer.

Radioiodination of Modified Porous Silica Nanoparticles as a Potential Candidate of Iodine-131 Drugs Vehicle

There are challenges related to cancer treatment, namely, targeting and biocompatibility associated with a drug vehicle. This research aims to prepare a theranostic cancer vehicle based on porous silica nanoparticles (PSN) with controllable nanoparticle size, supporting targeting properties, and biocompatible. The synthesis method combined the Stöber process and liquid crystal templating using a dispersant and pore expander. Triethanolamine (TEA) and Pluronic F-127 were combined as a steric stabilizer and dispersing agent, while n-hexane was used as a pore expander. The amine functionalization was carried out using the 3-aminopropyl-triethoxysilane solution. Furthermore, radiolabeling of PSN using Iodine-131 and iodogen as oxidizing agents was carried out. The results showed that the best achievable PSN size was 100-150 nm with a polydispersity index of 0.24 using TEA-Pluronic F-127. The functionalization results did not significantly affect the radioiodination result. Radiochemical purity (RCP) values up to 95% were obtained in the radioiodination, while the labeled compounds were relatively stable with 12 mCi radioactivity, indicating the absence of radiolysis. The synthesized PSN was not toxic to normal cell samples up to a concentration of 150 μg/mL for PSN and 170 μg/mL for PSN-NH2. The cellular uptake testing results of the PSN-131I in cancer cell samples showed promising uptake ability.

DMBA-induced Modulate Estrogen Receptors α and β Breast Cancer’s Animal Model

The high incidence of breast cancer cases in the world requires the use of applicative methods. The 7,12-dimethylbenz(a)anthracene (DMBA) induced breast cancer animal model is a widely used chemical-induced animal models for research on breast cancer. However, the molecular mechanism related to DMBA induction remains unclear. Good understanding on DMBA-induced animal models is crucial for studies related to future breast cancer treatments as animal models will provide a deeper understanding of anticancer medication, specifically those aimed for treating breast cancer. The aim of this study was to develop an DMBA-induced animal model for breast cancer. This study used female Wistar rats injected subcutaneously with DMBA as a carcinogen-induced agent (20 mg/kg) to induce tumor. Rat tumors were then evaluated and breast appearance was observed weekly, starting from day 28th after DMBA injection. Breast cancer tissue was then sampled and stored at -80°C until it was used for western blot and histological study. This study indicated that DMBA induced cancer in female Wistar rat’s breasts, and cytoplastic cells and lung metastatic was identified macroscopically and histopathologically. The metabolic sign was observed in the lung and breast sections. Interestingly, the DMBA induction in this study does not only induce organ cancers but also induces estrogen receptors and stimulates signaling of estrogen receptors α (ERα), ERβ, and Akt.

Synthesis, stability, and cellular uptake of 131I-estradiol against MCF7 and T-47D human cell lines as a radioligand for binding assay

Estradiol is a steroid hormone that works as an agonist estrogen receptor (ER). This compound is widely used as a ligand and bind specifically to the ERα. Radioligand binding assay is an in vitro method for drug development from natural products by synthesizing estradiol through radiolabeling using the radioiodination method. Synthesis of 131I-estradiol was perfomed by direct method using chloramine T as an oxidizer and by indirect labeling using 131I-histamine. The purity of chemical was determined by thin-layer chromatography and paper electrophoresis, as well as its stability for 30 days of storage in refrigerator, freezer and room temperature. The cellular uptake test of the radioligands from both methods was carried out with MCF7 and T-47D cell lines at 60 min. The results exhibited that 131I-estradiol was succesfully obtained with radiochemical purity greater than 95% and more stable in the refrigerator until 21 days than freezer and room temperature. 131I-estradiol and 131I-his-estradiol were internalized higher in T-47D cells than MCF7 cells (44.34 ± 5.93% vs. 17.27 ± 1.71% and 45.34 ± 6.42% vs. 4.92 ± 1.59%, respectively). Furthermore, the radioligands can be used to binding assay in determining the agonist or antagonist to ER of new drugs development.

Diagnosis of bladder cancer using 18F-labeled α-methyl-phenylalanine tracers in a mouse model

OBJECTIVE

Although 2-¹⁸F-fluoro-2-deoxy-glucose (¹⁸F-FDG) has established roles in the diagnosis of a variety of cancers, it has limited value in the detection of primary/recurrent lesions in the bladder, mainly because of interference by the pooled radioactivity in the urine. Our previous study revealed promising properties of L- and D-2-¹⁸F-α-methyl-phenylalanine (2-¹⁸F-FAMP) as radiotracers; i.e., their rapid blood clearance and low renal accumulation. In the present study we evaluated the utility of L- and D-2-¹⁸F-FAMP for imaging bladder cancer in a mouse model.

METHODS

We used the human bladder cancer cell line HT1376 to prepare a bladder cancer xenograft model in mice bearing both orthotopic and subcutaneous tumors. Biodistribution and PET imaging studies were performed at 1 and 3 h after injection of L-2-¹⁸F-FAMP or D-2-¹⁸F-FAMP. ¹⁸F-FDG was used as a control.

RESULTS

At 1 h after injection, greater accumulations of both L-2-¹⁸F-FAMP and D-2-¹⁸F-FAMP were observed in the orthotopic tumors compared to ¹⁸F-FDG. The orthotopic tumor-to-muscle ratio of D-2-¹⁸F-FAMP was significantly higher than that of ¹⁸F-FDG (p < 0.01), because of the rapid blood clearance of D-2-¹⁸F-FAMP. L-2-¹⁸F-FAMP showed the highest subcutaneous tumor-to-muscle ratio (p < 0.01) due to its high subcutaneous tumor uptake. Compared to L-2-¹⁸F-FAMP, D-2-¹⁸F-FAMP exhibited faster clearance and lower kidney accumulation. In the PET imaging studies, L- and D-2-¹⁸F-FAMP both clearly visualized the orthotopic bladder tumors at 1 h after injection.

CONCLUSION

Our study showed that L-2-¹⁸F-FAMP and D-2-¹⁸F-FAMP have the potential to detect bladder cancer.