Optical imaging detection of microscopic mammary cancer in ErbB-2 transgenic mice through the DA364 probe binding αv β3 integrins

Improved synthesis of DA364, an NIR fluorescence RGD probe targeting αvβ3 integrin

Optical imaging (OI) is gaining increasing attention in medicine as a non-invasive diagnostic imaging technology and as a useful tool for image-guided surgery. OI exploits the light emitted in the near-infrared region by fluorescent molecules able to penetrate living tissues. Cyanines are an important class of fluorescent molecules and by their conjugation to peptides it is possible to achieve optical imaging of tumours by selective targeting. We report here the improvements obtained in the synthesis of DA364, a small fluorescent probe (1.5 kDa) prepared by conjugation of pentamethine cyanine Cy5.5 to an RGD peptidomimetic, which can target tumour cells overexpressing integrin αvβ3 receptors.

RGD_PLGA Nanoparticles with Docetaxel: A Route for Improving Drug Efficiency and Reducing Toxicity in Breast Cancer Treatment

Breast cancer is the leading cause of cancer-related death in women. Although many therapeutic approaches are available, systemic chemotherapy remains the primary choice, especially for triple-negative and advanced breast cancers. Unfortunately, systemic chemotherapy causes serious side effects and requires high doses to achieve an effective concentration in the tumor. Thus, the use of nanosystems for drug delivery may overcome these limitations. Herein, we formulated Poly (lactic-co-glycolic acid) nanoparticles (PLGA-NPs) containing Docetaxel, a fluorescent probe, and a magnetic resonance imaging (MRI) probe. The cyclic RGD tripeptide was linked to the PLGA surface to actively target α_vβ₃ integrins, which are overexpressed in breast cancer. PLGA-NPs were characterized using dynamic light scattering, fast field-cycling ¹H-relaxometry, and ¹H-nuclear magnetic resonance. Their therapeutic effects were assessed both in vitro in triple-negative and HER2+ breast cancer cells, and in vivo in murine models. In vivo MRI and inductively coupled plasma mass spectrometry of excised tumors revealed a stronger accumulation of PLGA-NPs in the RGD_PLGA group. Targeted PLGAs have improved therapeutic efficacy and strongly reduced cardiac side effects compared to free Docetaxel. In conclusion, RGD-PLGA is a promising system for breast cancer treatment, with positive outcome in terms of therapeutic efficiency and reduction in side effects.

Preliminary safety and imaging efficacy of the near-infrared fluorescent contrast agent DA364 during fluorescence-guided surgery in dogs with spontaneous superficial tumors

Tumor-targeting contrast agents may facilitate resection of solid neoplasms during fluorescence-guided surgery. Preliminary safety and imaging efficacy of the near-infrared fluorescent probe DA364 were evaluated during surgical resection of spontaneous solid tumors in 24 dogs. Intra-operative imaging was performed in situ and on excised specimens to evaluate fluorescence intensities of tumor and adjacent tissues. After standard-of-care tumor resection, the wound bed was imaged again, and additional tissue was excised if residual fluorescence was detected.

DA364 was well tolerated after intravenous administration. The median tumor-to-background ratio in situ for mammary tumors, mast cell tumors and sarcomas was 1.8 (range 1.2–3.9), 2.2 (range 1.0–5.6), and 4.2 (range 2.0–4.3), respectively. Qualitative intra-operative tumor identification was feasible in half of the cases. Remaining fluorescence was detected in four wound beds that contained residual disease, and in11 tumor-free wound beds, confirmed by histopathology.

Overall, DA364 did not raise safety concerns and showed accumulation in different types of spontaneous tumors, showing potential to pinpoint residual disease. Larger clinical trials are necessary to select accurate dosing and imaging protocols for specific indications to evaluate the sensitivity and specificity of the agent.

NK cells control breast cancer and related cancer stem cell hematological spread

The growth and recurrence of a number of cancers is driven by a scarce population of cancer stem cells (CSCs), which are resistant to most current therapies. It has been shown previously that natural killer (NK) cells recognize human glioma, melanoma, colon and prostate CSCs in vitro. We herein show that human and mouse breast CSCs are also susceptible to NK cytotoxic activity in vitro. Moreover, CSC induced autologous NK cell activation and expansion in vivo, which correlate with the inhibition of CSC metastatic spread. These data suggest that NK cells control CSC metastatic spread in vivo and that their use in breast cancer therapy may well be fruitful.

Functional imaging of the angiogenic switch in a transgenic mouse model of human breast cancer by dynamic contrast enhanced magnetic resonance imaging

Tumour progression depends on several sequential events that include the microenvironment remodelling processes and the switch to the angiogenic phenotype, leading to new blood vessels recruitment. Non-invasive imaging techniques allow the monitoring of functional alterations in tumour vascularity and cellularity. The aim of this work was to detect functional changes in vascularisation and cellularity through Dynamic Contrast Enhanced (DCE) and Diffusion Weighted (DW) Magnetic Resonance Imaging (MRI) modalities during breast cancer initiation and progression of a transgenic mouse model (BALB-neuT mice). Histological examination showed that BALB-neuT mammary glands undergo a slow neoplastic progression from simple hyperplasia to invasive carcinoma, still preserving normal parts of mammary glands. DCE-MRI results highlighted marked functional changes in terms of vessel permeability (K(trans) , volume transfer constant) and vascularisation (vp , vascular volume fraction) in BALB-neuT hyperplastic mammary glands if compared to BALB/c ones. When breast tissue progressed from simple to atypical hyperplasia, a strong increase in DCE-MRI biomarkers was observed in BALB-neuT in comparison to BALB/c mice (K(trans)  = 5.3 ± 0.7E-4 and 3.1 ± 0.5E-4; vp  = 7.4 ± 0.8E-2 and 4.7 ± 0.6E-2 for BALB-neuT and BALB/c, respectively) that remained constant during the successive steps of the neoplastic transformation. Consistent with DCE-MRI observations, microvessel counting revealed a significant increase in tumour vessels. Our study showed that DCE-MRI estimates can accurately detect the angiogenic switch at early step of breast cancer carcinogenesis. These results support the view that this imaging approach is an excellent tool to characterize microvasculature changes, despite only small portions of the mammary glands developed neoplastic lesions in a transgenic mouse model.

The Promise of Preventive Cancer Vaccines

Years of unsuccessful attempts at fighting established tumors with vaccines have taught us all that they are only able to truly impact patient survival when used in a preventive setting, as would normally be the case for traditional vaccines against infectious diseases. While true primary cancer prevention is still but a long-term goal, secondary and tertiary prevention are already in the clinic and providing encouraging results. A combination of immunopreventive cancer strategies and recently approved checkpoint inhibitors is a further promise of forthcoming successful cancer disease control, but prevention will require a considerable reduction of currently reported toxicities. These considerations summed with the increased understanding of tumor antigens allow space for an optimistic view of the future.

A mathematical-biological joint effort to investigate the tumor-initiating ability of Cancer Stem Cells

The involvement of Cancer Stem Cells (CSCs) in tumor progression and tumor recurrence is one of the most studied subjects in current cancer research. The CSC hypothesis states that cancer cell populations are characterized by a hierarchical structure that affects cancer progression. Due to the complex dynamics involving CSCs and the other cancer cell subpopulations, a robust theory explaining their action has not been established yet. Some indications can be obtained by combining mathematical modeling and experimental data to understand tumor dynamics and to generate new experimental hypotheses. Here, we present a model describing the initial phase of ErbB2⁺ mammary cancer progression, which arises from a joint effort combing mathematical modeling and cancer biology. The proposed model represents a new approach to investigate the CSC-driven tumorigenesis and to analyze the relations among crucial events involving cancer cell subpopulations. Using in vivo and in vitro data we tuned the model to reproduce the initial dynamics of cancer growth, and we used its solution to characterize observed cancer progression with respect to mutual CSC and progenitor cell variation. The model was also used to investigate which association occurs among cell phenotypes when specific cell markers are considered. Finally, we found various correlations among model parameters which cannot be directly inferred from the available biological data and these dependencies were used to characterize the dynamics of cancer subpopulations during the initial phase of ErbB2⁺ mammary cancer progression.

Microenvironment, oncoantigens, and antitumor vaccination: lessons learned from BALB-neuT mice

The tyrosine kinase human epidermal growth factor receptor 2 (HER2) gene is amplified in approximately 20% of human breast cancers and is associated with an aggressive clinical course and the early development of metastasis. Its crucial role in tumor growth and progression makes HER2 a prototypic oncoantigen, the targeting of which may be critical for the development of effective anticancer therapies. The setup of anti-HER2 targeting strategies has revolutionized the clinical outcome of HER2⁺ breast cancer. However, their initial success has been overshadowed by the onset of pharmacological resistance that renders them ineffective. Since the tumor microenvironment (TME) plays a crucial role in drug resistance, the design of more effective anticancer therapies should depend on the targeting of both cancer cells and their TME as a whole. In this review, starting from the successful know-how obtained with a HER2⁺ mouse model of mammary carcinogenesis, the BALB-neuT mice, we discuss the role of TME in mammary tumor development. Indeed, a deeper knowledge of antigens critical for cancer outbreak and progression and of the mechanisms that regulate the interplay between cancer and stromal cell populations could advise promising ways for the development of the best anticancer strategy.

Genetically engineered mice as experimental tools to dissect the critical events in breast cancer

Elucidating the mechanism of pathogenesis of breast cancer has greatly benefited from breakthrough advances in both genetically engineered mouse (GEM) models and xenograft transplantation technologies. The vast array of breast cancer mouse models currently available is testimony to the complexity of mammary tumorigenesis and attempts by investigators to accurately portray the heterogeneity and intricacies of this disease. Distinct molecular changes that drive various aspects of tumorigenesis, such as alterations in tumor cell proliferation and apoptosis, invasion and metastasis, angiogenesis, and drug resistance have been evaluated using the currently available GEM breast cancer models. GEM breast cancer models are also being exploited to evaluate and validate the efficacy of novel therapeutics, vaccines, and imaging modalities for potential use in the clinic. This review provides a synopsis of the various GEM models that are expanding our knowledge of the nuances of breast cancer development and progression and can be instrumental in the development of novel prevention and therapeutic approaches for this disease.

Early onset and enhanced growth of autochthonous mammary carcinomas in C3-deficient Her2/neu transgenic mice

Aside from its classical role in fighting infections, complement is an important, although poorly understood, component of the tumor microenvironment. In particular, the tumor growth-regulatory activities of complement remain under debate. To assess the role of the complement system in the progression of autochthonous mammary carcinomas, we have crossed complement component 3 (C3)-deficient (C3^−/−) BALB/c male mice with BALB/c females expressing the activated rat Her2/neu oncogene (neuT). Although neuT transgenic mice develop spontaneous mammary cancers with 100% penetrance, a significantly shorter tumor latency (i.e., earlier onset of the first palpable tumor), a higher frequency of multiple tumors (multiplicity), and a dramatic increase in the tumor growth rate were found in neuT-C3^−/− animals. The accelerated tumor onset observed in neuT-C3^−/− mice was paralleled by an earlier onset of spontaneous lung metastases and by an increase in Her2 expression levels, primarily on the surface of tumor cells. The percentage of immune cells infiltrating neuT carcinomas was similar in C3-deficient and C3-proficient mice, with the exception of a significant increase in the frequency of regulatory T cells in neuT-C3^−/− tumors. Of particular interest, the enhanced immunosuppression imparted by C3 deficiency clearly influenced the immunogenic phenotype of autochthonous mammary tumors as neuT-C3^−/− malignant cells transplanted into syngeneic immunocompetent hosts gave rise to lesions with a significantly delayed kinetics and reduced incidence as compared with cells obtained from neuT C3-proficient tumors. Finally, increased blood vessel permeability was evident in neuT-C3^−/− tumors, although a similar number of tumor vessels was found in neuT and neuT-C3^−/− lesions. Altogether, these data suggest that complement plays a crucial role in the immunosurveillance and, possibly, the immunoediting of Her2-driven autochthonous mammary tumors.