Advances in PET and MRI imaging of tumor hypoxia

Expanding Role for Gallium-68 PET Imaging in Oncology

Gallium-68 has gained substantial momentum since 2003 as a versatile radiometal that is extremely useful for application in the development of novel oncology targeting diagnostic radiopharmaceuticals. It is available through both generator produced radioactivity and via cyclotron production methods and can therefore be implemented in either small- or large-scale production facilities. It can also be implemented within different spectrum of infrastructure settings with relative ease. Whilst many of the radiopharmaceuticals are being development and investigated, which is summarized in this manuscript, [68Ga]Ga-SSTR2 and [68Ga]Ga-PSMA has prominence in current clinical guidelines. The novel tracer [68Ga]Ga-FAPi has also gained significant interest in the clinical context. A comparison of the labelling strategies followed to incorporate gallium-68 and fluorine-18 into the same molecular targeting constructs clearly demonstrate that gallium-68 complexation is the most convenient approach. Recently, cold kit based starting products are available to make the small-scale production of gallium-68 radiopharmaceuticals even more efficient when combined with generator produced gallium-68. The regulatory aspects is currently changing to support the implementation of gallium-68 and other diagnostic radiopharmaceuticals, simplifying the translation towards clinical use. Overall, the development of gallium-68 based radiopharmaceuticals is not only rapidly changing the landscape of diagnosis in oncology, but this growth also promotes innovation and progress in new applications of therapeutic radiometals such as lutetium-177 and actinium-225.

Design and evaluation of a pneumatic actuation unit for a wasp-inspired self-propelled needle

Transperineal laser ablation is a minimally invasive thermo-ablative treatment for prostate cancer that requires the insertion of a needle for accurate optical fiber positioning. Needle insertion in soft tissues may cause tissue motion and deformation, resulting in tissue damage and needle positioning errors. In this study, we present a wasp-inspired self-propelled needle that uses pneumatic actuation to move forward with zero external push force, thus avoiding large tissue motion and deformation. The needle consists of six parallel 0.25-mm diameter Nitinol rods driven by a pneumatic actuation system. The pneumatic actuation system consists of Magnetic Resonance (MR) safe 3D-printed parts and off-the-shelf plastic screws. A self-propelled motion is achieved by advancing the needle segments one by one, followed by retracting them simultaneously. The advancing needle segment has to overcome a cutting and friction force, while the stationary needle segments experience a friction force in the opposite direction. The needle self-propels through the tissue when the friction force of the five stationary needle segments overcomes the sum of the friction and cutting forces of the advancing needle segment. We evaluated the prototype's performance in 10-wt% gelatin phantoms and ex vivo porcine liver tissue inside a preclinical Magnetic Resonance Imaging (MRI) scanner in terms of the slip ratio of the needle with respect to the phantom or liver tissue. Our results demonstrated that the needle was able to self-propel through the phantom and liver tissue with slip ratios of 0.912-0.955 and 0.88, respectively. The prototype is a promising step toward the development of self-propelled needles for MRI-guided transperineal laser ablation as a method to treat prostate cancer.

Diffuse reflectance spectroscopy for optical characterizations of orthotopic head and neck cancer models in vivo

We demonstrated an easy-to-build, portable diffuse reflectance spectroscopy device along with a Monte Carlo inverse model to quantify tissue absorption and scattering-based parameters of orthotopic head and neck cancer models in vivo. Both tissue-mimicking phantom studies and animal studies were conducted to verify the optical spectroscopy system and Monte Carlo inverse model for the accurate extraction of tissue optical properties. For the first time, we reported the tissue absorption and scattering coefficients of mouse normal tongue tissues and tongue tumor tissues. Our in vivo animal studies showed reduced total hemoglobin concentration, lower tissue vascular oxygen saturation, and increased tissue scattering in the orthotopic tongue tumors compared to the normal tongue tissues. Our data also showed that mice tongue tumors with different sizes may have significantly different tissue absorption and scattering-based parameters. Small tongue tumors (volume was ∼60 mm3) had increased absorption coefficients, decreased reduced-scattering coefficients, and increased total hemoglobin concentrations compared to tiny tongue tumors (volume was ∼18 mm3). These results demonstrated the potential of diffuse reflectance spectroscopy to noninvasively evaluate tumor biology using orthotopic tongue cancer models for future head and neck cancer research.

DKK2 promotes the progression of oral squamous cell carcinoma through the PI3K/AKT signaling pathway

OBJECTIVE

This study aimed to investigate the impact of Dickkopf 2 (DKK2) on the progression of oral squamous cell carcinoma (OSCC) and explore its role in the PI3K/AKT signaling transduction pathway.

MATERIALS AND METHODS

The study initially examined the expression of the DKK2 gene in OSCC tissues and normal tissues. Simultaneously, the expression of DKK2 in HOK cells and OSCC cells was verified, and changes in DKK2 expression under hypoxic conditions were detected. DKK2 overexpression and knockdown were performed in SCC-15 and CAL-27 cells. Subsequently, the effects of DKK2 on the proliferation, migration and invasion of OSCC were detected. Western blotting was employed to detect the expression of key proteins in the DKK2/PI3K/AKT signaling axis before and after transfection, and further explore the relevant molecular mechanisms.

RESULTS

Compared to normal tissues, DKK2 expression was elevated in OSCC tissues. The expression of DKK2 in the SCC-15 and CAL-27 cell lines was higher than that in HOK cells, and hypoxic conditions could promote DKK2 expression. DKK2 overexpression promoted cell proliferation, migration, and invasion, while DKK2 knockdown inhibited these processes. DKK2 overexpression activated the PI3K/AKT pathway, while DKK2 knockdown suppressed this pathway.

CONCLUSION

This study suggests that hypoxic conditions enhance the expression of DKK2 in OSCC. DKK2 regulates the proliferation, migration, and invasion of OSCC through the PI3K/AKT signaling pathway.

The development process of 'fit-for-purpose' imaging biomarkers to characterize the tumor microenvironment

Immune-based treatment approaches are successfully used for the treatment of patients with cancer. While such therapies can be highly effective, many patients fail to benefit. To provide optimal therapy choices and to predict treatment responses, reliable biomarkers for the assessment of immune features in patients with cancer are of significant importance. Biomarkers (BM) that enable a comprehensive and repeatable assessment of the tumor microenvironment (TME), the lymphoid system, and the dynamics induced by drug treatment can fill this gap. Medical imaging, notably positron emission tomography (PET) and magnetic resonance imaging (MRI), providing whole-body imaging BMs, might deliver such BMs. However, those imaging BMs must be well characterized as being 'fit for purpose' for the intended use. This review provides an overview of the key steps involved in the development of 'fit-for-purpose' imaging BMs applicable in drug development, with a specific focus on pharmacodynamic biomarkers for assessing the TME and its modulation by immunotherapy. The importance of the qualification of imaging BMs according to their context of use (COU) as defined by the Food and Drug Administration (FDA) and National Institutes of Health Biomarkers, EndpointS, and other Tools (BEST) glossary is highlighted. We elaborate on how an imaging BM qualification for a specific COU can be achieved.

Hypoxia-targeting bacteria in cancer therapy

Tumor hypoxia plays a crucial role in driving cancer progression and fostering resistance to therapies by contributing significantly to chemoresistance, radioresistance, angiogenesis, invasiveness, metastasis, altered cell metabolism, and genomic instability. Despite the challenges encountered in therapeutically addressing tumor hypoxia with conventional drugs, a noteworthy alternative has emerged through the utilization of anaerobic oncolytic bacteria. These bacteria exhibit a preference for accumulating and proliferating within the hypoxic regions of tumors, where they can initiate robust antitumor effects and immune responses. Through simple genetic manipulation or sophisticated synthetic bioengineering, these bacteria can be further optimized to improve safety and antitumor activities, or they can be combined synergistically with chemotherapies, radiation, or other immunotherapies. In this review, we explore the potential benefits and challenges associated with this innovative anticancer approach, addressing issues related to clinical translation, particularly as several strains have progressed to clinical evaluation.

Schiff bases and their metal complexes to target and overcome (multidrug) resistance in cancer

Overcoming multidrug resistance (MDR) is one of the major challenges in cancer therapy. In this respect, Schiff base-related compounds (bearing a R1R2CNR3 bond) gained high interest during the past decades. Schiff bases are considered privileged ligands for various reasons, including the easiness of their preparation and the possibility to form complexes with almost all transition metal ions. Schiff bases and their metal complexes exhibit many types of biological activities and are used for the treatment and diagnosis of various diseases. Until now, 13 Schiff bases have been investigated in clinical trials for cancer treatment and hypoxia imaging. This review represents the first collection of Schiff bases and their complexes which demonstrated MDR-reversal activity. The areas of drug resistance covered in this article involve: 1) Modulation of ABC transporter function, 2) Targeting lysosomal ABCB1 overexpression, 3) Circumvention of ABC transporter-mediated drug efflux by alternative routes of drug uptake, 4) Selective activity against MDR cancer models (collateral sensitivity), 5) Targeting GSH-detoxifying systems, 6) Overcoming apoptosis resistance by inducing necrosis and paraptosis, 7) Reactivation of mutated p53, 8) Restoration of sensitivity to DNA-damaging anticancer therapy, and 9) Overcoming drug resistance through modulation of the immune system. Through this approach, we would like to draw attention to Schiff bases and their metal complexes representing highly interesting anticancer drug candidates with the ability to overcome MDR.

A Review of Hypoxia Imaging Using 18F-Fluoromisonidazole Positron Emission Tomography

Tumor hypoxia is an essential factor related to malignancy, prognosis, and resistance to treatment. Positron emission tomography (PET) is a modality that visualizes the distribution of radiopharmaceuticals administered into the body. PET imaging with [18F]fluoromisonidazole ([18F]FMISO) identifies hypoxic tissues. Unlike [18F]fluorodeoxyglucose ([18F]FDG)-PET, fasting is not necessary for [18F]FMISO-PET, but the waiting time from injection to image acquisition needs to be relatively long (e.g., 2-4 h). [18F]FMISO-PET images can be displayed on an ordinary commercial viewer on a personal computer (PC). While visual assessment is fundamental, various quantitative indices such as tumor-to-muscle ratio have also been proposed. Several novel hypoxia tracers have been invented to compensate for the limitations of [18F]FMISO.

A Luciferase Reporter Assay to Detect Cellular Hypoxia In Vitro

Hypoxia is a hallmark of ischemic cardiovascular diseases and solid malignant tumors. Cellular hypoxia induces numerous physiological and pathological processes, including hematopoiesis, angiogenesis, metabolic changes, cell growth, and apoptosis. Hypoxia-inducible factor-1 (HIF-1) binds to hypoxia response elements (HREs) to selectively induce the expression of various genes in response to hypoxia. Therefore, HREs have been used to develop hypoxia-targeted gene therapy.More than 70 pairs of HREs and hypoxia-inducible genes have been identified. The hypoxia-induced gene expression levels vary among HRE sequences depending on the number of HRE copies and oxygen levels. Most known HREs have not yet been thoroughly studied. Recent studies have revealed that the HRE-mediated effects of hypoxia are cell line-dependent. Herein we describe an in vitro method to investigate gene activation levels and characteristics based on varying the copy number of HREs in response to cellular hypoxia. We explain how to clone HREs into luciferase reporter constructs in the sense, antisense, and dual directions to measure luciferase expression for functional analyses.