Histopathological growth patterns as a candidate biomarker for immunomodulatory therapy

The encroachment of a growing tumor upon the cells and structures of surrounding normal tissue results in a series of histopathological growth patterns (HGPs). These morphological changes can be assessed in hematoxylin-and-eosin (H&E) stained tissue sections from primary and metastatic tumors and have been characterized in a range of tissue types including liver, lung, lymph node and skin. HGPs in different tissues share certain general characteristics like the extent of angiogenesis, but also appropriate tissue-specific mechanisms which ultimately determine differences in the biology of HGP subtypes. For instance, in the well-characterized HGPs of liver metastases, the two main subtypes, replacement and desmoplastic, recapitulate two responses of the normal liver to injury: regeneration and fibrosis. HGP subtypes have distinct cytokine profiles and differing levels of lymphocytic infiltration which suggests that they are indicative of immune status in the tumor microenvironment. HGPs predict response to bevacizumab and are associated with overall survival (OS) after surgery for liver metastases in colorectal cancer (CRC). In addition, HGPs can change over time in response to therapy. With standard scoring methods being developed, HGPs represent an easily accessible, dynamic biomarker to consider when determining strategies for treatment using anti-VEGF and immunomodulatory drugs.

Histopathological growth patterns of liver metastasis: updated consensus guidelines for pattern scoring, perspectives and recent mechanistic insights

The first consensus guidelines for scoring the histopathological growth patterns (HGPs) of liver metastases were established in 2017. Since then, numerous studies have applied these guidelines, have further substantiated the potential clinical value of the HGPs in patients with liver metastases from various tumour types and are starting to shed light on the biology of the distinct HGPs. In the present guidelines, we give an overview of these studies, discuss novel strategies for predicting the HGPs of liver metastases, such as deep-learning algorithms for whole-slide histopathology images and medical imaging, and highlight liver metastasis animal models that exhibit features of the different HGPs. Based on a pooled analysis of large cohorts of patients with liver-metastatic colorectal cancer, we propose a new cut-off to categorise patients according to the HGPs. An up-to-date standard method for HGP assessment within liver metastases is also presented with the aim of incorporating HGPs into the decision-making processes surrounding the treatment of patients with liver-metastatic cancer. Finally, we propose hypotheses on the cellular and molecular mechanisms that drive the biology of the different HGPs, opening some exciting preclinical and clinical research perspectives.

Association between the histopathological growth patterns of liver metastases and survival after hepatic surgery in breast cancer patients

Currently, there are no markers to identify patients with liver-only or liver-dominant metastases that would benefit from hepatic surgery. Here we characterized histopathological growth patterns (HGPs) of liver metastases in a consecutive series of 36 breast cancer patients who underwent hepatic surgery. Survival analyses showed that the presence of a desmoplastic HGP in the liver metastases (a rim of fibrous tissue separating cancer cells from the liver parenchyma, present in 20 (56%) patients) is independently associated with favorable progression-free and overall survival when compared with the replacement HGP (cancer cells growing into the liver parenchyma, present in 16 (44%) patients).

Molecular characterization of the histopathological growth patterns of colorectal cancer liver metastases by RNA sequencing of targeted samples at the tumor-liver interface

The behaviour of metastases in patients with liver-metastatic colorectal cancer (CRC) is still not adequately considered during treatment planning. However, studies in large cohorts have shown that the disease course in these patients depends on the histopathological growth pattern (HGP) of the liver metastases, with the desmoplastic (or encapsulated) pattern responsible for a favourable outcome and the replacement pattern for an unfavourable course. To increase our knowledge of cancer biology in general as well as to design clinical trials that take into account the diverse behaviour of liver metastases, it is necessary to know the cellular and molecular determinants of these growth patterns. For that purpose, we compared the transcriptome of tumour tissue (prospective cohort; n = 57) sampled very precisely at the transition of metastasis and adjacent liver, between the desmoplastic and replacement HGP. In addition, the mutational profiles for 46 genes related to CRC were extracted from the RNA sequencing reads. First, we show that the genetic constitution of a liver metastasis from colorectal cancer does not determine its HGP. Second, we show clear differences between HGPs regarding the expression of genes belonging to the Molecular Signatures Database hallmark gene sets. Biological themes of the replacement HGP reflect cancer cell proliferation and glucose metabolism, while the desmoplastic HGP is characterized by inflammation and immune response, and angiogenesis. This study supports the view that HGPs are a reflection of the biology of CRC liver metastases and suggests the HGPs are driven epigenetically rather than by specific gene mutations.

Histopathological growth patterns and tumor-infiltrating lymphocytes in breast cancer liver metastases

Liver is the third most common organ for breast cancer (BC) metastasis. Two main histopathological growth patterns (HGP) exist in liver metastases (LM): desmoplastic and replacement. Although a reduced immunotherapy efficacy is reported in patients with LM, tumor-infiltrating lymphocytes (TIL) have not yet been investigated in BCLM. Here, we evaluate the distribution of the HGP and TIL in BCLM, and their association with clinicopathological variables and survival. We collect samples from surgically resected BCLM (n = 133 patients, 568 H&E sections) and post-mortem derived BCLM (n = 23 patients, 97 H&E sections). HGP is assessed as the proportion of tumor liver interface and categorized as pure-replacement ('pure r-HGP') or any-desmoplastic ('any d-HGP'). We score the TIL according to LM-specific guidelines. Associations with progression-free (PFS) and overall survival (OS) are assessed using Cox regressions. We observe a higher prevalence of 'any d-HGP' (56%) in the surgical samples and a higher prevalence of 'pure r-HGP' (83%) in the post-mortem samples. In the surgical cohort, no evidence of the association between HGP and clinicopathological characteristics is observed except with the laterality of the primary tumor (p value = 0.049) and the systemic preoperative treatment before liver surgery (p value = .039). TIL is less prevalent in 'pure r-HGP' as compared to 'any d-HGP' (p value = 0.001). 'Pure r-HGP' predicts worse PFS (HR: 2.65; CI: (1.45-4.82); p value = 0.001) and OS (HR: 3.10; CI: (1.29-7.46); p value = 0.011) in the multivariable analyses. To conclude, we demonstrate that BCLM with a 'pure r-HGP' is associated with less TIL and with the worse outcome when compared with BCLM with 'any d-HGP'. These findings suggest that HGP could be considered to refine treatment approaches.

Transcriptomic characterization of the histopathological growth patterns in breast cancer liver metastases

Metastatic breast cancer (mBC) remains incurable and liver metastases (LM) are observed in approximately 50% of all patients with mBC. In some cases, surgical resection of breast cancer liver metastases (BCLM) is associated with prolonged survival. However, there are currently no validated marker to identify these patients. The interactions between the metastatic cancer cells and the liver microenvironment result in two main histopathological growth patterns (HGP): replacement (r-HGP), characterized by a direct contact between the cancer cells and the hepatocytes, and desmoplastic (d-HGP), in which a fibrous rim surrounds the tumor cells. In patients who underwent resection of BCLM, the r-HGP is associated with a worse postoperative prognosis than the d-HGP. Here, we aim at unraveling the biological differences between these HGP within ten patients presenting both HGP within the same metastasis. The transcriptomic analyses reveal overexpression of genes involved in cell cycle, DNA repair, vessel co-option and cell motility in r-HGP while angiogenesis, wound healing, and several immune processes were found overexpressed in d-HGP LM. Understanding the biology of the LM could open avenues to refine treatment of BC patients with LM.

Abstract PD9-08: Breast cancer liver metastases vascularize by vessel co-option, not angiogenesis, and have a desert immune phenotype: A histopathological and gene expression study

Phase 3 trials of bevacizumab combined with chemotherapy in metastatic breast cancer have consistently failed to demonstrate a survival benefit for the addition of bevacizumab. When cancers metastasize to highly vascular organs (including the liver), they can utilize vessel co-option, instead of angiogenesis, as a mechanism to obtain a vascular supply (1). We have repeatedly shown by histopathological analyses that almost all (95%, 2 cohorts) breast cancer liver metastases utilize vessel co-option instead of angiogenesis to vascularize (2,3). The prevalence of vessel co-option in breast cancer could explain, at least in part, why anti-angiogenic therapy has been a disappointing therapeutic approach in metastatic breast cancer. Animal models of non-angiogenic liver and lung metastases also displayed resistance to anti-VEGF treatment (3,4).

We have now undertaken a gene expression study (mRNA sequencing) of targeted samples at the tumor-liver interface to discover gene expression patterns and signaling pathways that are associated with non-angiogenic growth of metastatic cancer in the liver (n = 70).

A network to detect biological themes of non-angiogenic growth was built by gene set enrichment analysis. Key components of this network are: cancer cell motility and invasion, epithelial-to-mesenchymal transition, stemness and proliferation. This contrasts with the network of angiogenic liver metastases of which the most important components are inflammation and ECM remodeling. Semi-automated image analyses of CD8-immunostained section of liver metastases confirms that non-angiogenic liver metastases have a significantly lower density of CD8-positive cytotoxic T-lymphocytes at the tumor-liver interface when compared with angiogenic liver metastases (300 cells/mm2 and 1000 cells/mm2, respectively (p<0.0001)). In addition, a clear CXCL13-driven B-cell gene expression signature is associated with angiogenic growth of liver mets but is absent in non-angiogenic growth of breast cancer liver metastases. Gene expression patterns that may be play a role in vessel co-option are the up-regulation of LAMA3, LAMB3, LAMC2, coding for the 3 subunits of laminin-5, and of ITGA3, ITGB1, ITGA6 and ITGB4, coding for both integrin-receptors of laminin-5. This supports the concept of 'adhesive' vessel co-option during which cancer cells use the basement membrane of the co-opted blood vessels as a soil (5). In addition, the claudin-2 gene (CLDN2) is significantly overexpressed in non-angiogenic liver metastases which is consistent with earlier reports on the role of claudin-2 during breast cancer metastasis to the liver (6).

In conclusion, we provide evidence, based on morphology and gene expression, for the almost exclusive non-angiogenic growth of breast cancer liver metastases. In addition, non-angiogenic breast cancer liver metastases are characterized by a desert immune phenotype. Both observations can have an impact on the treatment strategy of patients with metastatic breast cancer.

References: 1. 10.1038/nrc.2018.14 – 2. 10.1038/sj.bjc.6601727 – 3. 10.1038/nm.4197 – 4. 10.1002/path.4845 – 5. 10.1097/NEN.0b013e318233afd7 – 6. 10.1038/onc.2010.518

Citation Format: Vermeulen PB, van Dam P-J, Daelemans S, Latacz E, Joye I, Kockx M, Dirix P, Verhoef K, Grunhagen D, Huget P, Van Laere S, Dirix LY. Breast cancer liver metastases vascularize by vessel co-option, not angiogenesis, and have a desert immune phenotype: A histopathological and gene expression study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD9-08.