Vascularization of colorectal carcinoma liver metastasis: insight into stratification of patients for anti‐angiogenic therapies

Abstract

Current treatment for metastatic disease targets angiogenesis. With the increasing data demonstrating that cancer cells do not entirely rely on angiogenesis but hijack the existing vasculature through mechanisms such as co‐option of existing blood vessels, identification of targets has become of utmost importance. Our study looks at the vasculature of chemonaïve and treated colorectal carcinoma liver metastases (CRCLMs) to obtain a basic understanding of the microvessel density, type of vasculature (mature versus immature), and correlation with histopathological growth patterns that demonstrate unique patterns of angiogenesis. We performed immunohistochemistry on chemonaïve sections of desmoplastic histopathological growth pattern (DHGP) and replacement histopathological growth patterns (RHGP) lesions with CD31 [endothelial cell (EC) marker] and CD34/Ki67 double staining, which denotes proliferating ECs. The CD31 stains demonstrated a lower microvascular CD31 +ve capillary density in the DHGP versus RHGP lesions; and integrating both immunostains with CD34/Ki67 staining on serial sections revealed proliferating vessels in DHGP lesions and co‐option of mature existing blood vessels in RHGP lesions. Interestingly, upon treatment with chemotherapy and bevacizumab, the RHGP lesions showed no necrosis whereas the DHGP lesions had almost 100% necrosis of the cancer cells and in most cases there was a single layer of viable cancer cells, just under or within the desmoplastic ring. The survival of these cells may be directly related to spatial location and possibly a different microenvironment, which may involve adhesion to different extracellular matrix components and/or different oxygen/nutrient availability. This remains to be elucidated. We provide evidence that DHGP CRCLMs obtain their blood supply via sprouting angiogenesis whereas RHGP lesions obtain their blood supply via co‐option of existing vasculature. Furthermore current treatment regimens do not affect RHGP lesions and although they kill the majority of the cancer cells in DHGP lesions, there are cells surviving within or adjacent to the desmoplastic ring which could potentially give rise to a growing lesion.

Angiopoietin1 Deficiency in Hepatocytes Affects the Growth of Colorectal Cancer Liver Metastases (CRCLM)

“…Ten lesions for each treatment groups were used, with a distribution of DHGP: n = 5 and RHGP: n = 5. These were serial sections from the same samples used in our previous paper, which indicated no difference in expression of VEGF in naïve vs treated samples [22]. However, in both chemo and chemo plus Bev treated RHGP lesions, the positivity of Ang1 remained high at the adjacent normal of the tumor, with no significant difference when compared to the chemonaïve samples ( Figure S2).…”

“…We have previously shown that desmoplastic lesions contain immature vessels, whereas replacement lesions contain mature vessels, supporting the role of vessel co-option [22]. To investigate the vascular factors involved in co-option, we performed IHC staining on human CRCLM samples using antibodies to Ang1, Ang2 and Tie2.…”

“…To investigate the vascular factors involved in co-option, we performed IHC staining on human CRCLM samples using antibodies to Ang1, Ang2 and Tie2. In order to correlate our previous vascular characterization using CD31, CD34//Ki67 and VEGFA with the current study, we used serial sections from the same samples used in our previous paper [22]. IHC staining was performed on a total of twenty-three chemonaïve lesions (DHGP: n = 11 and RHGP: n = 12).…”

“…Furthermore, RHGP lesions showed that the expression of Ang1 was significantly increased in the center of the tumor after treatment with chemo and not chemo plus Bev (p-value < 0.005) ( Figure S2). No comparison with DHGP lesions is possible since the treated groups contain less than 10% viable tumor cells and cannot be evaluated [22].…”

Critical considerations for targeting colorectal liver metastases with nanotechnology

“…Liver metastases with a replacement pattern grow without inducing hypoxia or angiogenesis. Instead they co-opt the preexisting sinusoidal vasculature and have little effect on the existing liver architecture, that is, not causing inflammation and fibrosis (Kuczynski, Vermeulen, Pezzella, Kerbel, & Reynolds, 2019;Lazaris et al, 2018;van Dam et al, 2017;Van den Eynden et al, 2013). In contrast, metastases with a pushing and to a lesser degree desmoplastic growth pattern display signs of active, hypoxia-driven angiogenesis.…”