Molecular Imaging of Post-Src Inhibition Tumor Signatures for Guiding Dasatinib Combination Therapy

BCL2L11 Induction Mediates Sensitivity to Src and MEK1/2 Inhibition in Thyroid Cancer

Patients with advanced thyroid cancer, including advanced papillary thyroid cancer and anaplastic thyroid cancer (ATC), have low survival rates because of the lack of efficient therapies available that can combat their aggressiveness. A total of 90% of thyroid cancers have identifiable driver mutations, which often are components of the MAPK pathway, including BRAF, RAS, and RET-fusions. In addition, Src is a non-receptor tyrosine kinase that is overexpressed and activated in thyroid cancer, which we and others have shown is a clinically relevant target. We have previously demonstrated that combined inhibition of Src with dasatinib and the MAPK pathway with trametinib synergistically inhibits growth and induces apoptosis in BRAF- and RAS-mutant thyroid cancer cells. Herein, we identified the pro-apoptotic protein BCL2L11 (BIM) as being a key mediator of sensitivity in response to combined dasatinib and trametinib treatment. Specifically, cells that are sensitive to combined dasatinib and trametinib treatment have inhibition of FAK/Src, MEK/ERK, and AKT, resulting in the dramatic upregulation of BIM, while cells that are resistant lack inhibition of AKT and have a dampened induction of BIM. Inhibition of AKT directly sensitizes resistant cells to combined dasatinib and trametinib but will not be clinically feasible. Importantly, targeting BCL-XL with the BH3-mimeitc ABT-263 is sufficient to overcome lack of BIM induction and sensitize resistant cells to combined dasatinib and trametinib treatment. This study provides evidence that combined Src and MEK1/2 inhibition is a promising therapeutic option for patients with advanced thyroid cancer and identifies BIM induction as a potential biomarker of response.

Paradigms in Fluorescence Molecular Imaging: Maximizing Measurement of Biological Changes in Disease, Therapeutic Efficacy, and Toxicology/Safety

Fluorescence molecular imaging (MI) is an important concept in preclinical research that focuses on the visualization of cellular and biological function in a non-invasive fashion to better understand in vivo disease processes and treatment effects. MI differs fundamentally from traditional preclinical imaging strategies in that it generally relies on reporter probes specific for particular targets or pathways that can be used to reveal biological changes in situ, at the site(s) of disease. In contrast, the more established imaging modalities, like magnetic resonance imaging, X-ray, micro X-ray computed tomography, and ultrasound, historically have relied primarily on late-stage anatomical or physiologic changes. The practical application of fluorescence MI, however, has drifted somewhat from the emphasis on quantifying biology, and based on the publication record, it now appears to include any imaging in which a probe or contrast agent is used to non-invasively acquire in vivo endpoint information. Unfortunately, the mere use of a defined biologically specific probe, in the absence of careful study design, does not guarantee that any useful biological information is actually gained, although often useful endpoint results still can be achieved. This review proposes to add subcategories of MI, termed MI biological assessment (or MIBA), that emphasize a focus on obtaining early and clear biological changes associated with disease development, therapeutic efficacy, and drug-induced tissue changes. Proper selection of probes and careful study design are critical for maximizing the non-invasive assessment of in vivo biological changes, and applications of these critical elements are described.

Tyrosine kinase inhibition to improve anthracycline-based chemotherapy efficacy in T-cell lymphoma

BACKGROUND

Anthracycline-containing regimens, namely cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) or CHOEP (CHOP + etoposide), represent the current standard of care for patients with newly diagnosed peripheral T-cell lymphomas (PTCLs), although responses are unsatisfactory. In this study, we investigated the pathways able to mitigate the sensitivity to CHOP-based regimens in preclinical models of T-cell lymphoma (TCL) to select agents for the development of CHOP-based drug combinations.

METHODS

We performed gene expression profiling of malignant T-cell lines exposed to CHOEP; flow cytometry was employed to study the effects of drug combinations on cell viability, cell cycle distribution, apoptosis and mitochondrial membrane depolarisation. Western blot analyses were performed to study cell signalling downstream of the T-cell receptor and apoptosis. The in vivo effect of the drug combination was tested in xenograft models.

RESULTS

We highlighted a modulation of tyrosine kinases belonging to the T-cell receptor pathway upon chemotherapy that provided the rationale for combining the tyrosine kinase inhibitor dasatinib with CHOEP. Dasatinib improves CHOEP activity and reduces viability in vitro. Furthermore, combination treatment results in tumour growth inhibition in in vivo xenograft mouse models.

CONCLUSIONS

Our data provide the rationale for clinical testing of the dasatinib-CHOEP combination in patients with T-cell lymphoma.

Inhibiting Metastasis and Preventing Tumor Relapse by Triggering Host Immunity with Tumor-Targeted Photodynamic Therapy Using Photosensitizer-Loaded Functional Nanographenes

Effective cancer therapy depends not only on destroying the primary tumor but also on conditioning the host immune system to recognize and eliminate residual tumor cells and prevent metastasis. In this study, a tumor integrin αvβ6-targeting peptide (the HK peptide)-functionalized graphene oxide (GO) was coated with a photosensitizer (HPPH). The resulting GO conjugate, GO(HPPH)-PEG-HK, was investigated whether it could destroy primary tumors and boost host antitumor immunity. We found that GO(HPPH)-PEG-HK exhibited significantly higher tumor uptake than GO(HPPH)-PEG and HPPH. Photodynamic therapy (PDT) using GO(HPPH)-PEG suppressed tumor growth in both subcutaneous and lung metastatic mouse models. Necrotic tumor cells caused by GO(HPPH)-PEG-HK PDT activated dendritic cells and significantly prevented tumor growth and lung metastasis by increasing the infiltration of cytotoxic CD8⁺ T lymphocytes within tumors as evidenced by in vivo optical and single-photon emission computed tomography (SPECT)/CT imaging. These results demonstrate that tumor-targeted PDT using GO(HPPH)-PEG-HK could effectively ablate primary tumors and destroy residual tumor cells, thereby preventing distant metastasis by activating host antitumor immunity and suppressing tumor relapse by stimulation of immunological memory.

Noninvasive Imaging of CD206-Positive M2 Macrophages as an Early Biomarker for Post-Chemotherapy Tumor Relapse and Lymph Node Metastasis

Tumor relapse after initial regression post-chemotherapy is a major challenge in cancer treatment, as it usually leads to local-regional recurrence or inoperable distant metastasis. M2 macrophages diminish the tumor-inhibitory effect of chemotherapy and correlate with distant metastasis and poor prognosis. In this study, we investigated whether molecular imaging of M2 macrophages could serve as an early biomarker for tumor relapse after chemotherapy and tumor lymph node metastasis in preclinical mouse models. Methods: We developed M2 macrophage-targeted probes for near-infrared fluorescence (NIRF) imaging and single-photon emission computed tomography (SPECT) using an anti-CD206 monoclonal antibody. The specific targeting capacity and potential applications of the NIRF and SPECT probes were investigated in subcutaneous tumor and lymph node metastasis models of 4T1 murine breast cancer. Results: M2 macrophage infiltration was significantly increased in the 4T1 tumors that later underwent relapse but not in non-relapsing 4T1 tumors after cyclophosphamide treatment. Through NIRF imaging and SPECT using our synthesized probes, the infiltration of M2 macrophages in relapsing tumors and tumor lymph node metastasis could be sensitively detected. Importantly, early prediction of tumor relapse by molecular imaging of M2 macrophages resulted in an effective eradication of tumors upon combination with additional radiotherapy. Conclusion: Our findings demonstrate that M2 macrophage-targeted imaging allows for noninvasively predicting post-chemotherapy tumor relapse and sensitively detecting the metastatic lymph nodes in vivo. This imaging strategy could provide a better understanding of cancer progression, enable early prediction of tumor resistance, and have implications on the rational design of cancer therapeutics.

Optimization of Early Response Monitoring and Prediction of Cancer Antiangiogenesis Therapy via Noninvasive PET Molecular Imaging Strategies of Multifactorial Bioparameters

Objective: Antiangiogenesis therapy (AAT) has provided substantial benefits regarding improved outcomes and survival for suitable patients in clinical settings. Therefore, the early definition of therapeutic effects is urgently needed to guide cancer AAT. We aimed to optimize the early response monitoring and prediction of AAT efficacy, as indicated by the multi-targeted anti-angiogenic drug sunitinib in U87MG tumors, using noninvasive positron emission computed tomography (PET) molecular imaging strategies of multifactorial bioparameters.

Methods: U87MG tumor mice were treated via intragastric injections of sunitinib (80 mg/kg) or vehicle for 7 consecutive days. Longitudinal MicroPET/CT scans with ¹⁸F-FDG, ¹⁸F-FMISO, ¹⁸F-ML-10 and ¹⁸F-Alfatide II were acquired to quantitatively measure metabolism, hypoxia, apoptosis and angiogenesis on days 0, 1, 3, 7 and 13 following therapy initiation. Tumor tissues from a dedicated group of mice were collected for immunohistochemical (IHC) analysis of key biomarkers (Glut-1, CA-IX, TUNEL, α_νβ₃ and CD31) at the time points of PET imaging. The tumor sizes and mouse weights were measured throughout the study. The tumor uptake (ID%/g_max), the ratios of the tumor/muscle (T/M) for each probe, and the tumor growth ratios (TGR) were calculated and used for statistical analyses of the differences and correlations.

Results: Sunitinib successfully inhibited U87MG tumor growth with significant differences in the tumor size from day 9 after sunitinib treatment compared with the control group (P < 0.01). The uptakes of ¹⁸F-FMISO (reduced hypoxia), ¹⁸F-ML-10 (increased apoptosis) and ¹⁸F-Alfatide II (decreased angiogenesis) in the tumor lesions significantly changed during the early stage (days 1 to 3) of sunitinib treatment; however, the uptake of ¹⁸F-FDG (increased glucose metabolism) was significantly different during the late stage. The PET imaging data of each probe were all confirmed via ex vivo IHC of the relevant biomarkers. Notably, the PET imaging of ¹⁸F-Alfatide II and ¹⁸F-FMISO was significantly correlated (all P < 0.05) with TGR, whereas the imaging of ¹⁸F-FDG and ¹⁸F-ML-10 was not significantly correlated with TGR.

Conclusion: Based on the tumor uptake of the PET probes and their correlations with MVD and TGR, ¹⁸F-Alfatide II PET may not only monitor the early response but also precisely predict the therapeutic efficacy of the multi-targeted, anti-angiogenic drug sunitinib in U87MG tumors. In conclusion, it is feasible to optimize the early response monitoring and efficacy prediction of cancer AAT using noninvasive PET molecular imaging strategies of multifactorial bioparameters, such as angiogenesis imaging with ¹⁸F-Alfatide II, which represents an RGD-based probe.

Enhanced Anti-Tumor Efficacy through a Combination of Integrin αvβ6-Targeted Photodynamic Therapy and Immune Checkpoint Inhibition

“Training” the host immune system to recognize and systemically eliminate residual tumor lesions and micrometastases is a promising strategy for cancer therapy. In this study, we investigated whether integrin αvβ6-targeted photodynamic therapy (PDT) of tumors using a phthalocyanine dye-labeled probe (termed DSAB-HK) could trigger the host immune response, and whether PDT in combination with anti-PD-1 immune checkpoint inhibition could be used for the effective therapy of primary tumors and metastases. By near-infrared fluorescence imaging, DSAB-HK was demonstrated to specifically target either subcutaneous tumors in a 4T1 mouse breast cancer model or firefly luciferase stably transfected 4T1 (4T1-fLuc) lung metastatic tumors. Upon light irradiation, PDT by DSAB-HK significantly inhibited the growth of subcutaneous 4T1 tumors, and in addition promoted the maturation of dendritic cells and their production of cytokines, which subsequently stimulated the tumor recruitment of CD8⁺ cytotoxic T lymphocytes. Furthermore, DSAB-HK PDT of the first tumor followed by PD-1 blockade markedly suppressed the growth of a second subcutaneous tumor, and also slowed the growth of 4T1-fLuc lung metastasis as demonstrated by serial bioluminescence imaging. Together, our results demonstrated the synergistic effect of tumor-targeted PDT and immune checkpoint inhibition for improving anti-tumor immunity and suppressing tumor growth/metastasis.