Twenty years after: the beautiful hypothesis and the ugly facts

Morphological Characteristics and Clinical Significance of Different Types of Tumor Vessels in Patients with Stages I-IIA of Squamous Cervical Cancer

The determination of factors associated with progression of cervical cancer is important, both for a recurrence risk assessment and for determining optimal treatment tactics. Previously, we showed the prognostic value of different types of tumor microvessels (MVs) in gastric and breast cancer. The object of this research was to study the morphology and clinical significance of different tumor microvessels in early cervical cancer. A total of 65 archived paraffin blocks of patients with I-IIA stages of squamous cervical cancer were investigated. Samples were stained with Mayer hematoxylin and immunohistochemically using antibodies to CD34, podoplanin, HIF-1a, and Snail. The eight types of tumor MVs differed in morphology were identified. It was established that only the dilated capillaries (DСs) with weak expression of CD34, the contact type DCs, the capillaries in tumor solid component, and the lymphatic vessels in the lymphoid and polymorphic cell infiltrates of tumor stroma are associated with clinical and pathological characteristics of early cervical cancer. Preliminary results also suggest that a combination of fragmentation in tumor solid component and the contact type DCs may predict a recurrence of early cervical cancer. Given the small number of cervical cancer recurrences, the predictive significance of the described markers requires a more thorough examination.

Anti-angiogenic Treatment in Metastatic Colorectal Cancer: Current Issues and Future Aims

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Blocking angiogenesis represents a fundamental process in Colorectal Cancer (CRC) treatment. VEGF (vascular endothelial growth factor) pathway is implicated in various processes that regulate tumor vascularization and proliferation. In the last years, great efforts have been made thanks to the discovery of targeted drugs that block VEGF and its receptors conferring a benefit in a variety of tumors, including CRC. To date, four drugs have been approved for the treatment of metastatic CRC (mCRC): bevacizumab, aflibercept, ramucirumab and regorafenib. Unfortunately, patients relapse due to the appearance of resistance. The VEGF family, its role in the angiogenesis and complex heterogeneity of mechanisms that escape tumor blockade are not completely understood and there is a lack of biomarkers of response to anti-angiogenic drugs. We describe the principal mechanisms of resistance to anti-VEGF therapy and discuss potential biomarkers to be investigated in the near future.

Vessel co-option in glioblastoma: emerging insights and opportunities

Vessel co-option is the movement of cancer cells towards and along the pre-existing vasculature and is an alternative to angiogenesis to gain access to nutrients. Vessel co-option has been shown as a strategy employed by some glioblastoma (GBM) cells to invade further into the brain, leading to one of the greatest challenges in treating GBM. In GBM, vessel co-option may be an intrinsic feature or an acquired mechanism of resistance to anti-angiogenic treatment. Here, we describe the histological features and the dynamics visualized through intravital microscopy of vessel co-option in GBM, as well as the molecular players discovered until now. We also highlight key unanswered questions, as answering these is critical to improve understanding of GBM progression and for developing more effective approaches for GBM treatment.

Tumor vasculature: a sally port for inhibiting cancer cell spreading

The close relationship between metastasis and establishment of tumor vasculature has inspired enormous research interests aiming to suppress metastasis via inhibiting the development of tumor vasculature. International experts gathered in Guangzhou, China on May 10–12, 2018 in The 4th International Meeting of Cancer and Blood Vessels to discuss the multiple ways for solid tumors to establish their vasculature. Vessel co-option is a mean by which a solid tumor takes advantage of the existing or newly induced blood vessels in the surrounding normal tissues to sustain tumor growth and metastasis. The underlying mechanisms of vessel co-option, the roles of pericyte, and the potential novel therapeutic targets have been discussed in the meeting.

Collateral Damage Intended-Cancer-Associated Fibroblasts and Vasculature Are Potential Targets in Cancer Therapy

After oncogenic transformation, tumor cells rewire their metabolism to obtain sufficient energy and biochemical building blocks for cell proliferation, even under hypoxic conditions. Glucose and glutamine become their major limiting nutritional demands. Instead of being autonomous, tumor cells change their immediate environment not only by their metabolites but also by mediators, such as juxtacrine cell contacts, chemokines and other cytokines. Thus, the tumor cells shape their microenvironment as well as induce resident cells, such as fibroblasts and endothelial cells (ECs), to support them. Fibroblasts differentiate into cancer-associated fibroblasts (CAFs), which produce a qualitatively and quantitatively different extracellular matrix (ECM). By their contractile power, they exert tensile forces onto this ECM, leading to increased intratumoral pressure. Moreover, along with enhanced cross-linkage of the ECM components, CAFs thus stiffen the ECM. Attracted by tumor cell- and CAF-secreted vascular endothelial growth factor (VEGF), ECs sprout from pre-existing blood vessels during tumor-induced angiogenesis. Tumor vessels are distinct from EC-lined vessels, because tumor cells integrate into the endothelium or even mimic and replace it in vasculogenic mimicry (VM) vessels. Not only the VM vessels but also the characteristically malformed EC-lined tumor vessels are typical for tumor tissue and may represent promising targets in cancer therapy.