Pro-tumoral immune cell alterations in wild type and Shb-deficient mice in response to 4T1 breast carcinomas.

Xiujuan Li,Ganlin Zhang,Mariela Mejia-Cordova,Björn Lindahl,Stellan Sandler,Zhengkang Luo,Kailash Singh,Michael Welsh,Maria Jamalpour

doi:10.18632/oncotarget.24643

Abstract

To assess mechanisms responsible for breast carcinoma metastasis, 4T1 breast carcinomas were grown orthotopically in wild type or Shb knockout mice. Tumor growth, metastasis, vascular characteristics and immune cell properties were analyzed. Absence of Shb did not affect tumor growth although it increased lung metastasis. Shb knockout mouse tumors showed decreased redness and less developed vascular plexa located at the periphery of the tumors. No difference in overall tumor vascular density, leakage or pericyte coverage was noted between the genotypes although the average vessel size was smaller in the knockout. Tumors induced an increase of CD11b+ cells in spleen, lymph node, thymus, bone marrow and blood. Numbers of Shb knockout CD11b/CD8+ cells were decreased in lymph nodes and bone marrow of tumor bearing mice. Mice with tumors had reduced numbers of CD4+ lymphocytes in blood/lymphoid organs, whereas in most of these locations the proportion of CD4+ cells co-expressing FoxP3 was increased, suggesting a relative increase in Treg cells. This finding was reinforced by increased blood interleukin-35 (IL-35) in wild type tumor bearing mice. Shb knockout blood showed in addition an increased proportion of IL-35 expressing Treg cells, supporting the notion that absence of Shb further promotes tumor evasion from immune cell recognition. This could explain the increased number of lung metastases observed under these conditions. In conclusion, 4T1 tumors alter immune cell responses that promote tumor expansion, metastasis and escape from T cell recognition in an Shb dependent manner.

Highlights

Metastasis is usually the ultimate cause of cancerinduced death in patients afflicted by breast carcinoma
Tumors grown on wild type mice exhibited prominent vascular plexa at the periphery of the tumors (Figure 2A) and these were significantly more pronounced compared with tumors grown on Shb knockout mice (Figure 2B), which probably www.oncotarget.com explains the red appearance of the wild type tumors (Figure 1B)
There was no difference in vascular density between the genotypes, the tumors grown on knockout mice had more but smaller vessels (Figure 2C-2F), suggesting that different angiogenic cues were operating under these conditions

Summary

Introduction

Metastasis is usually the ultimate cause of cancerinduced death in patients afflicted by breast carcinoma. This is a complicated multi-step process, involving epithelial-mesodermal transition (EMT), vascular and lymphatic leakage, decreased pericyte coverage, promotion of tumor cell expansion by stromal cells such as tumorassociated macrophages, escape from immune surveillance mechanisms and the ability to seed at distant locations [1]. Concerning breast cancer, several reports indicate that immune suppressing regulatory T (Treg) cells become activated and prevalent in both blood and the tumor [10,11,12]. It has been reported that CD8+ T cells play a major anti-tumoral role in breast carcinomas, further emphasizing the relevance of Tregs in this scenario [18]. An increase of circulating IL-35 has been demonstrated in patients with breast cancer compared to healthy controls [19]

Methods

Results

Conclusion