Radiotheranostic Targeting Cancer Stem Cells in Human Colorectal Cancer Xenografts

Nanobiotechnology augmented cancer stem cell guided management of cancer: liquid-biopsy, imaging, and treatment

Cancer stem cells (CSCs) represent both a key driving force and therapeutic target of tumoral carcinogenesis, tumor evolution, progression, and recurrence. CSC-guided tumor diagnosis, treatment, and surveillance are strategically significant in improving cancer patients' overall survival. Due to the heterogeneity and plasticity of CSCs, high sensitivity, specificity, and outstanding targeting are demanded for CSC detection and targeting. Nanobiotechnologies, including biosensors, nano-probes, contrast enhancers, and drug delivery systems, share identical features required. Implementing these techniques may facilitate the overall performance of CSC detection and targeting. In this review, we focus on some of the most recent advances in how nanobiotechnologies leverage the characteristics of CSC to optimize cancer diagnosis and treatment in liquid biopsy, clinical imaging, and CSC-guided nano-treatment. Specifically, how nanobiotechnologies leverage the attributes of CSC to maximize the detection of circulating tumor DNA, circulating tumor cells, and exosomes, to improve positron emission computed tomography and magnetic resonance imaging, and to enhance the therapeutic effects of cytotoxic therapy, photodynamic therapy, immunotherapy therapy, and radioimmunotherapy are reviewed.

Molecular Biomarkers and Signaling Pathways of Cancer Stem Cells in Colorectal Cancer

Colorectal cancer (CRC) is the third most frequently found cancer in the world, and it is frequently discovered when it is already far along in its development. About 20% of cases of CRC are metastatic and incurable. There is more and more evidence that colorectal cancer stem cells (CCSCs), which are in charge of tumor growth, recurrence, and resistance to treatment, are what make CRC so different. Because we know more about stem cell biology, we quickly learned about the molecular processes and possible cross-talk between signaling pathways that affect the balance of cells in the gut and cancer. Wnt, Notch, TGF-β, and Hedgehog are examples of signaling pathway members whose genes may change to produce CCSCs. These genes control self-renewal and pluripotency in SCs and then decide the function and phenotype of CCSCs. However, in terms of their ability to create tumors and susceptibility to chemotherapeutic drugs, CSCs differ from normal stem cells and the bulk of tumor cells. This may be the reason for the higher rate of cancer recurrence in patients who underwent both surgery and chemotherapy treatment. Scientists have found that a group of uncontrolled miRNAs related to CCSCs affect stemness properties. These miRNAs control CCSC functions like changing the expression of cell cycle genes, metastasis, and drug resistance mechanisms. CCSC-related miRNAs mostly control signal pathways that are known to be important for CCSC biology. The biomarkers (CD markers and miRNA) for CCSCs and their diagnostic roles are the main topics of this review study.

Cancer Stem Cells in Colorectal Cancer: Implications for Targeted Immunotherapies

PURPOSE

Colorectal cancers are composed of heterogeneous cell populations in the concepts of genetic and functional degrees that among them cancer stem cells are identified with their self-renewal and stemness capability mediating primary tumorigenesis, metastasize, therapeutic resistance, and tumor recurrence. Therefore, understanding the key mechanisms of stemness in colorectal cancer stem cells (CRCSCs) provides opportunities to discover new treatments or improve existing therapeutic regimens.

METHODS

We review the biological significance of stemness and the results of potential CRCSC-based targeted immunotherapies. Then, we pointed out the barriers to targeting CRCSCs in vivo and highlight new strategies based on synthetic and biogenic nanocarriers for the development of future anti-CRCSC trials.

RESULTS

The CSCs' surface markers, antigens, neoantigens, and signaling pathways supportive CRCSCs or immune cells that are interacted with CRCSCs could be targeted by immune monotherapy or in formulation with developed nanocarriers to overcome the resistant mechanisms in immune evader CRCSCs.

CONCLUSION

Identification molecular and cellular cues supporting stemness in CRCSCs and their targeting by nanoimmunotherpy can improve the efficacy of existed therapies or explore novel therapeutic options in future.

A comprehensive update of micro- and nanobubbles as theranostics in oncology

Advances in diagnostic and imaging capabilities have allowed cancers to be detected earlier and characterized more robustly. These strategies have recently branched into theranostics whereby contrast agents traditionally used for imaging have been co-loaded with therapeutics to simultaneously diagnose and treat cancers in a patient-specific manner. Microbubbles (MB) and nanobubbles (NB) are contrast agents which can be modulated to meet the theranostic needs particularly in the realm of oncology. The current review focuses on the ultrasound-responsive MB/NB platforms used as a theranostic tool in oncology. We discuss in detail the key parameters that influence the utility of MB/NB formulations and implications of such treatment modalities. Recent advances in composition strategies, latest works in the pre-clinical stages and multiple paradigm-shifting innovations in the field of MB/NB are discussed in-depth in this review. The clinical application of MB/NB is currently limited to diagnostic imaging. Surface chemistry modification strategies will help tune the formulations toward therapeutic applications. It is also anticipated that MB/NB will see increased use to deliver gas therapeutics. Scalability and stability considerations will be at the forefront as these particles get introduced into the clinical theranostic toolbox.

Development of a Stable Peptide-Based PET Tracer for Detecting CD133-Expressing Cancer Cells

CD133 has been recognized as a prominent biomarker for cancer stem cells (CSCs), which promote tumor relapse and metastasis. Here, we developed a clinically relevant, stable, and peptide-based positron emission tomography (PET) tracer, [64Cu]CM-2, for mapping CD133 protein in several kinds of cancers. Through the incorporation of a 6-aminohexanoic acid (Ahx) into the N terminus of a CM peptide, we constructed a stable peptide tracer [64Cu]CM-2, which exhibited specific binding to CD133-positive CSCs in multiple preclinical tumor models. Both PET imaging and ex vivo biodistribution verified the superb performance of [64Cu]CM-2. Furthermore, the matched physical and biological half-life of [64Cu]CM-2 makes it a state-of-the-art PET tracer for CD133. Therefore, [64Cu]CM-2 PET may not only enable the longitudinal tracking of CD133 dynamics in the cancer stem cell niche but also provide a powerful and noninvasive imaging tool to track down CSCs in refractory cancers.

Peptide-based 68Ga-PET radiotracer for imaging CD133 expression in colorectal cancer

OBJECTIVE

CD133 is a demonstrated cancer stem cell marker. A small peptide LS7, screened by a phage display technique, was identified to specifically target CD133. The purpose of this study was to develop a novel and specific peptide-based PET imaging agent for CD133 imaging in colorectal cancer.

METHODS

The peptide LS7 was conjugated with 1,4,7,20-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and radiolabeled with 68Ga. The cellular uptake was assessed in vitro. In vivo small-animal PET/CT and ex vivo biodistribution evaluations were performed in mice bearing CD133-positive HCT116 and Lovo cell-derived tumors as well as CD133-negative DLD1 cell-derived tumors. Nonspecific uptake of the tracer in HCT116 cell-derived tumor cells and tumor models was determined by coincubation or coinjection with an excess of unlabeled DOTA-LS7 along with radiolabeled tracers.

RESULTS

68Ga-DOTA-LS7 was produced with 80.0% yield and the radiochemical purity was greater than 95.0%. In vitro, 68Ga-DOTA-LS7 was selectively taken up by HCT116 and Lovo cells but not by DLD1 cells. Small-animal PET/CT clearly revealed deposition of 68Ga-DOTA-LS7 in HCT116 and Lovo cell-derived tumors with excellent contrast. Biodistribution demonstrated that the tumor uptakes were 2.24 ± 0.16, 1.76 ± 0.42, and 0.69 ± 0.28% ID/g in HCT116, Lovo and DLD1 cell-derived tumors, respectively, at 90 min post-injection. Uptake of 68Ga-DOTA-LS7 in HCT116 tumors was significantly inhibited by coinjection of excess DOTA-LS7.

CONCLUSION

Rapid tumor CD133 detection and selectivity were demonstrated in vitro and in vivo with PET using the specific CD133 binding peptide 68Ga-DOTA-LS7. A robust correlation was detected in vivo between tumor signals from mouse xenograft models with different cell lines and CD133 expression. The favorable characteristics of 68Ga-DOTA-LS7, such as convenient synthesis and specific uptake, warrant its further investigation for CD133 expression imaging.

Molecular Immunotherapy: Promising Approach to Treat Metastatic Colorectal Cancer by Targeting Resistant Cancer Cells or Cancer Stem Cells

The immune system is able to recognize and eliminate tumor cells. Some tumors, including colorectal cancer (CRC), induce immune tolerance via different mechanisms of “immunoediting” and “immune evasion” and can thus escape immune surveillance. The impact of immunotherapy on cancer has been investigated for many years, but so far, the application was limited to few cancer types. Immuno-oncological therapeutic strategies against metastatic colorectal cancer (mCRC), the adaptive immune system activating approaches, offer a high potential for adaptation to the great heterogeneity of CRC. Moreover, novel treatment approaches are currently being tested that might specifically target the disease initiating and maintaining population of colorectal cancer stem cells (CSCs). In this review, we aim to summarize the current state of immune-oncology and tumor immunotherapy of patients with mCRC and discuss different therapeutic modalities that focus on the activation of tumor-specific T-cells and their perspectives such as tumor vaccination, checkpoint inhibition, and adoptive T-cell transfer or on the eradication of colorectal CSCs.