Tumor-associated high endothelial venules mediate lymphocyte entry into tumors and predict response to PD-1 plus CTLA-4 combination immunotherapy

Recruitment of lymphocytes into tumors is critical for anti-tumor immunity and efficacious immunotherapy. We show in murine models that tumor-associated high endothelial venules (TA-HEVs) are major sites of lymphocyte entry into tumors at baseline and upon treatment with anti-PD-1/anti-CTLA-4 immune checkpoint blockade (ICB). TA-HEV endothelial cells (TA-HECs) derive from post-capillary venules, co-express MECA-79⁺ HEV sialomucins and E/P-selectins, and are associated with homing and infiltration into tumors of various T cell subsets. Intravital microscopy further shows that TA-HEVs are the main sites of lymphocyte arrest and extravasation into ICB-treated tumors. Increasing TA-HEC frequency and maturation increases the proportion of tumor-infiltrating stem-like CD8⁺ T cells, and ameliorates ICB efficacy. Analysis of tumor biopsies from 93 patients with metastatic melanoma reveals that TA-HEVs are predictive of better response and survival upon treatment with anti-PD-1/anti-CTLA-4 combination. These studies provide critical insights into the mechanisms governing lymphocyte trafficking in cancer immunity and immunotherapy.

Hypoxia-inducible factor 1-mediated characteristic features of cancer cells for tumor radioresistance

Tumor hypoxia has been attracting increasing attention in the fields of radiation biology and oncology since Thomlinson and Gray detected hypoxic cells in malignant solid tumors and showed that they exert a negative impact on the outcome of radiation therapy. This unfavorable influence has, at least partly, been attributed to cancer cells acquiring a radioresistant phenotype through the activation of the transcription factor, hypoxia-inducible factor 1 (HIF-1). On the other hand, accumulating evidence has recently revealed that, even though HIF-1 is recognized as an important regulator of cellular adaptive responses to hypoxia, it may not become active and induce tumor radioresistance under hypoxic conditions only. The mechanisms by which HIF-1 is activated in cancer cells not only under hypoxic conditions, but also under normoxic conditions, through cancer-specific genetic alterations and the resultant imbalance in intermediate metabolites have been summarized herein. The relevance of the HIF-1-mediated characteristic features of cancer cells, such as the production of antioxidants through reprogramming of the glucose metabolic pathway and cell cycle regulation, for tumor radioresistance has also been reviewed.

Noninvasive Dynamic Imaging of Tumor Early Response to Nanoparticle-mediated Photothermal Therapy

In spite of rapidly increasing interest in the use of nanoparticle-mediated photothermal therapy (PTT) for treatment of different types of tumors, very little is known on early treatment-related changes in tumor response. Using graphene oxide (GO) as a model nanoparticle (NP), in this study, we tracked the changes in tumors after GO NP-mediated PTT by magnetic resonance imaging (MRI) and quantitatively identified MRI multiple parameters to assess the dynamic changes of MRI signal in tumor at different heating levels and duration. We found a time- and temperature-dependent dynamic change of the MRI signal intensity in intratumor microenvironment prior to any morphological change of tumor, mainly due to quick and effective eradication of tumor blood vessels. Based on the distribution of GO particles, we also demonstrated that NP-medited PTT caused heterogeneous thermal injury of tumor. Overall, these new findings provide not only a clinical-related method for non-invasive early tracking, identifying, and monitoring treatment response of NP-mediated PTT but also show a new vision for better understanding mechanisms of NP-mediated PTT.

Crosstalk between tumor blood vessels heterogeneity and hormonal profile of pituitary adenomas: evidence and controversies

AIM

Pituitary adenomas are intracranial tumors with controversial histopathology and heterogeneous clinical behaviour. Angiogenesis and tumor blood vessels' role in pathogenesis, remain one of the great pituitary tumor mysteries. No connection between tumor vessel heterogeneity, hormonal profile and biological behaviour has been reported. We aimed to study pituitary adenomas blood vessels concerning their immature, intermediate or mature phenotype and microvessel density, correlated with immunohistochemical hormonal profile and hormone values in serum and cerebrospinal fluid.

MATERIALS AND METHODS

We classified pituitary adenomas according to hormone profile and we applied a double immunostaining highlighting both endothelial and perivascular cells for a more accurate assessment of blood vessel types.

RESULTS

Overall microvessel density was found to be highest in growth hormone-secreting adenomas (48.51 ± 12.15) and lowest in prolactinomas (29.15 ± 18.78). When we differentially counted tumor blood vessels we observed a predominance of immature and intermediate blood vessels compared to mature ones. A significant correlation was found between immature tumor blood vessels and tissue prolactin expression, as assessed by immunhistochemistry (p=0.044). A partial correlation was found between serum (p=0.036) and cerebrospinal prolactin values (p=0.006) with immature and intermediate blood vessels. Also, a partial correlation has been reported only between mature blood vessels and cerebrospinal fluid prolactin values (p=0.008). No correlation was obtained for other types of pituitary adenomas.

CONCLUSION

Our results suggest a strong involvement of prolactin with a dual role in pituitary adenomas vasculature remodelling by acting both on endothelial and perivascular cells, a finding that could partially explain discrepancies between clinical diagnosis and hormonal profile.

Spatial-temporal FUCCI imaging of each cell in a tumor demonstrates locational dependence of cell cycle dynamics and chemoresponsiveness

The phase of the cell cycle can determine whether a cancer cell can respond to a given drug. We report here on the results of monitoring of real-time cell cycle dynamics of cancer cells throughout a live tumor intravitally using a fluorescence ubiquitination cell cycle indicator (FUCCI) before, during, and after chemotherapy. In nascent tumors in nude mice, approximately 30% of the cells in the center of the tumor are in G₀/G₁ and 70% in S/G₂/M. In contrast, approximately 90% of cancer cells in the center and 80% of total cells of an established tumor are in G₀/G₁ phase. Similarly, approximately 75% of cancer cells far from (> 100 µm) tumor blood vessels of an established tumor are in G₀/G₁. Longitudinal real-time imaging demonstrated that cytotoxic agents killed only proliferating cancer cells at the surface and, in contrast, had little effect on quiescent cancer cells, which are the vast majority of an established tumor. Moreover, resistant quiescent cancer cells restarted cycling after the cessation of chemotherapy. Our results suggest why most drugs currently in clinical use, which target cancer cells in S/G₂/M, are mostly ineffective on solid tumors. The results also suggest that drugs that target quiescent cancer cells are urgently needed.

Tissue-penetrating delivery of compounds and nanoparticles into tumors

Poor penetration of drugs into tumors is a major obstacle in tumor treatment. We describe a strategy for peptide-mediated delivery of compounds deep into the tumor parenchyma that uses a tumor-homing peptide, iRGD (CRGDK/RGPD/EC). Intravenously injected compounds coupled to iRGD bound to tumor vessels and spread into the extravascular tumor parenchyma, whereas conventional RGD peptides only delivered the cargo to the blood vessels. iRGD homes to tumors through a three-step process: the RGD motif mediates binding to alphav integrins on tumor endothelium and a proteolytic cleavage then exposes a binding motif for neuropilin-1, which mediates penetration into tissue and cells. Conjugation to iRGD significantly improved the sensitivity of tumor-imaging agents and enhanced the activity of an antitumor drug.