Tumor-Derived Factors Differentially Affect the Recruitment and Plasticity of Neutrophils

Our plain-English summary of Tumor-Derived Factors Differentially Affect the Recruitment and Plasticity of Neutrophils, by L. Arpinati, N. Kaisar-Iluz, M.E. Shaul, et al (Cancers, 2021).

The study

• Authors: L. Arpinati, N. Kaisar-Iluz, M.E. Shaul, C. Groth, V. Umansky, Z.G. Fridlender
• Journal: Cancers
• Published: 2021;13(20)
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Neutrophils play a key role in cancer biology. In contrast to circulating normal-density neutrophils (NDN), the amount of low-density neutrophils (LDN) significantly increases with tumor progression. The correlation between these neutrophil subpopulations and intratumoral neutrophils (TANs) is still under debate. Using 4T1 (breast) and AB12 (mesothelioma) tumor models, we aimed to elucidate the source of TANs and to assess the mechanisms driving neutrophils' plasticity in cancer. Both NDN and LDN were found to migrate in response to CXCL1 and CXCL2 exposure, and co-infiltrate the tumor site ex vivo and in vivo, although LDN migration into the tumor was higher than NDN. Tumor-derived factors and chemokines, particularly CXCL1, were found to drive neutrophil phenotypical plasticity, inducing NDN to transition towards a low-density state (LD-NDN). LD-NDN appeared to differ from NDN by displaying a phenotypical profile similar to LDN in terms of nuclear morphology, surface receptor markers, decreased phagocytic abilities, and increased ROS production. Interestingly, all three subpopulations displayed comparable cytotoxic abilities towards tumor cells. Our data suggest that TANs originate from both LDN and NDN, and that a portion of LDN derives from NDN undergoing phenotypical changes. NDN plasticity resulted in a change in surface marker expression and functional activity, gaining characteristics of LDN.

In plain English

This was a laboratory study in mice; it did not study asbestos exposure. The authors used two mouse tumor lines: AB12, a malignant mesothelioma line from an asbestos-induced tumor, and 4T1, a breast cancer line. They compared two kinds of blood neutrophils, normal-density (NDN) and low-density (LDN), from tumor-bearing female Balb/C mice. Tested separately in tumor slices, LDN entered both tumor types more than NDN; tested together, LDN entered more only in 4T1 slices. In living mice, both kinds reached tumors comparably. CXCL1 and CXCL2 drew both kinds in lab tests; CXCL12 and G-CSF did not. Some NDN shifted to a low-density state. Medium from 4T1 tumor cells increased this shift in cells from both models, AB12 medium only in AB12-derived cells. CXCL1 raised it in AB12-derived cells from 2.4% to 5.4%, not in 4T1-derived cells. Blocking CXCR2 lowered it in both; blocking TGF-beta lowered it in AB12-derived cells. Shifted cells resembled LDN in several respects. All three groups reduced breast tumor cell growth similarly. The authors concluded that tumor neutrophils can come from both kinds and that some LDN may arise from NDN. No human samples were used.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Animal and laboratory experiment (mouse tumor models, with in vitro, ex vivo tumor-slice and in vivo cell-transfer tests)
• Who was studied: Female Balb/C mice aged five to seven weeks, bearing AB12 (mesothelioma) or 4T1 (breast cancer) tumors, housed at the Hebrew University School of Medicine, Israel; neutrophils isolated from their blood. The total number of mice is not stated.
• Exposure: No asbestos exposure was studied. The AB12 mesothelioma cell line came from an asbestos-induced mouse tumor. Neutrophils were exposed to tumor-conditioned media and to the factors CXCL1, CXCL2, CXCL12, G-CSF and TNF-alpha, a CXCR2 inhibitor, and an anti-TGF-beta antibody.
• Main results:
  • In tumor slices tested separately, LDN infiltrated both AB12 and 4T1 tumors to a greater extent than NDN.
  • When NDN and LDN were added together to tumor slices, LDN infiltrated more than NDN in the 4T1 model (p = 0.0075), with no difference in AB12.
  • After injection into tumor-bearing mice, NDN and LDN co-infiltrated tumors in comparable amounts in both models (n = 2, performed in two separate experiments).
  • In the 4T1 model, the CXCR2 receptor was found on 91.99 plus or minus 3.5% of NDN and 65.56 plus or minus 6.71% of LDN, but on only 1.80 plus or minus 1.21% of tumor-associated neutrophils.
  • CXCL1 and CXCL2 strongly induced migration of both NDN and LDN in vitro to similar extents. CXCL12 and G-CSF did not.
  • In plain medium, 4T1-derived NDN shifted to a low-density state more often than AB12-derived NDN (8.61 plus or minus 0.91% vs. 4.66 plus or minus 0.77%). Few LDN shifted to high density (1.04 plus or minus 0.27% of AB12-LDN; 0.68 plus or minus 0.05% of 4T1-LDN).
  • 4T1 tumor-conditioned medium raised the NDN shift to 14.01 plus or minus 2.51% in AB12-NDN and to 32.13 plus or minus 4.13% in 4T1-NDN.
  • AB12 tumor-conditioned medium raised the shift in AB12-NDN to 13.06 plus or minus 2.07% (p = 0.035) but did not affect 4T1-derived NDN.
  • CXCL1 increased the shift of AB12-derived NDN from 2.4% to 5.4% (p = 0.0013). CXCL1 had no effect on 4T1-derived NDN, and TNF-alpha and G-CSF had no influence in either model.
  • Blocking CXCR2 lowered the NDN shift in tumor-conditioned medium from 25.55 to 19.02% in AB12-derived neutrophils (p = 0.0332) and from 36.56 to 16.82% in 4T1-derived neutrophils (p = 0.0484).
  • Blocking TGF-beta lowered the shift in AB12-derived neutrophils from 17.12 plus or minus 4.10% to 11.92 plus or minus 2.59% (p = 0.0429).
  • Fewer shifted cells (LD-NDN) than NDN expressed the marker CD39 (25.12 plus or minus 10.36% vs. 61.34 plus or minus 8.28%).
  • Immature cells (rounded nuclei) made up 28.95 plus or minus 3.08% of LD-NDN compared with 17.44 plus or minus 1.54% of NDN.
  • NDN showed significantly higher phagocytic capability than both LDN and LD-NDN.
  • After PMA stimulation, LD-NDN released significantly more ROS than NDN (p = 0.0221).
  • NDN, LDN and LD-NDN all significantly decreased 4T1 tumor cell proliferation in a similar manner.
• The authors' conclusion: The authors concluded that tumor-associated neutrophils can originate from both NDN and LDN, probably through CXCR2 and CXCR4 activation, with a mild preference for LDN infiltration. They also concluded that cancer-related LDN could partly originate from NDN undergoing tumor-induced changes, with the CXCL1/CXCR2 axis playing a role.
• Limitations the authors state:
  • No human samples were included, which limits assessment of clinical significance in human cancer patients.
  • In vitro culture conditions may have influenced the finding of similar migration of NDN and LDN toward CXCL1 and CXCL2.
  • Other receptors for CXCL1 and CXCL2 (for example CXCR1) were not evaluated and might have affected migration.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma.

Related studies

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• Expression of the Wilms' tumor gene WT1 in human malignant mesothelioma cell lines and relationship to platelet-derived growth factor A and insulin-like growth factor 2 expression — A.W. Langerak, K.A. Williamson, et al. (1995)
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• Methylation-derived Neutrophil-to-Lymphocyte Ratio and Lung Cancer Risk in Heavy Smokers — L. Grieshober, S. Graw, et al. (2018)
• Are macrophages, myeloid derived suppressor cells and neutrophils mediators of local suppression in healthy and cancerous tissues in aging hosts? — C. Jackaman, D.J. Nelson (2014)

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