Gastroenterology

Gastroenterology

Volume 144, Issue 1, January 2013, Pages 155-166
Gastroenterology

Original Research
Basic and Translational—Alimentary Tract
Mice That Express Human Interleukin-8 Have Increased Mobilization of Immature Myeloid Cells, Which Exacerbates Inflammation and Accelerates Colon Carcinogenesis

https://doi.org/10.1053/j.gastro.2012.09.057Get rights and content

Background & Aims

Interleukin (IL)-8 has an important role in initiating inflammation in humans, attracting immune cells such as neutrophils through their receptors CXCR1 and CXCR2. IL-8 has been proposed to contribute to chronic inflammation and cancer. However, mice do not have the IL-8 gene, so human cancer cell lines and xenograft studies have been used to study the role of IL-8 in colon and gastric carcinogenesis. We generated mice that carry a bacterial artificial chromosome that encompasses the entire human IL-8 gene, including its regulatory elements (IL-8Tg mice).

Methods

We studied the effects of IL-8 expression in APCmin+/− mice and IL-8Tg mice given azoxymethane and dextran sodium sulfate (DSS). We also examined the effects of IL-8 expression in gastric cancer in INS-GAS mice that overexpress gastrin and IL-8Tg mice infected with Helicobacter felis.

Results

In IL-8Tg mice, expression of human IL-8 was controlled by its own regulatory elements, with virtually no messenger RNA or protein detectable under basal conditions. IL-8 was strongly up-regulated on systemic or local inflammatory stimulation, increasing mobilization of immature CD11b+Gr-1+ myeloid cells (IMCs) with thioglycolate-induced peritonitis, DSS-induced colitis, and H. felis–induced gastritis. IL-8 was increased in colorectal tumors from patients and IL-8Tg mice compared with nontumor tissues. IL-8Tg mice developed more tumors than wild-type mice following administration of azoxymethane and DSS. Expression of IL-8 increased tumorigenesis in APCmin+/− mice compared with APCmin+/− mice that lack IL-8; this was associated with increased numbers of IMCs and angiogenesis in the tumors.

Conclusions

IL-8 contributes to gastrointestinal carcinogenesis by mobilizing IMCs and might be a therapeutic target for gastrointestinal cancers.

Section snippets

Isolation and Characterization of a Bacterial Artificial Chromosome

A human bacterial artificial chromosome (hBAC; RPL11-997L11) encompassing the entire IL-8 gene was purchased through CHORI (Oakland, CA) (Supplementary Figure 2A). To ascertain proper IL-8 gene splicing in mouse cells, the hBAC plasmid (20 μg) was transfected into mouse dendritic DC2.4 cells that were subsequently treated with 50 ng/mL of mouse IL-1β. Polymerase chain reaction (PCR) using IL-8–specific primers in different exons confirmed proper splicing of IL-8 (see Supplementary Materials and

IL-8 Expression Is Increased in Colorectal Tumors and Contributes to Enhanced Intestinal Carcinogenesis in Humans and IL-8Tg Mice

To confirm that IL-8 plays a role in colon cancer in humans, we examined IL-8 expression in colonic tumors of patients undergoing colorectal cancer resection for stage II or stage III colon cancer. Using real-time quantitative reverse-transcription PCR, we detected significantly increased levels of IL-8 messenger RNA (mRNA) in colonic tumors compared with adjacent normal colonic tissue from the same patients (n = 10) (Figure 1A).

Given that mice lack the IL-8 gene, we used a BAC approach to

Discussion

In this study, we used a BAC encompassing the entire IL-8 gene regulatory elements to generate IL-8–expressing transgenic mice that recapitulate human physiologic IL-8 expression. Transgenic mouse models expressing constitutively high levels of hIL-8 have previously been reported20, 21; however, none have exhibited a physiologic pattern of IL-8 expression with strict inducibility by injury or infection. Here, we show that IL-8 BAC transgenic mice do not exhibit detectable circulating IL-8 at

Acknowledgements

Gene microarray accession number: Gene Expression Omnibus number GSE 39273.

The authors thank Dr Vundavalli Murty for fluorescent in situ hybridization analysis and Dr Rong-Zhen Chen for performing immunostaining.

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported by National Institutes of Health grants R01CA93405, R01DK060758, 1U54CA126513, and R01CA120979 (to T.C.W.) as well as a Canadian Institutes of Health Research Clinician Scientist Phase I Award and an Alberta Heritage Foundation for Medical Research Clinical Fellowship Award (to S.A.).

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    Authors share co-first authorship.

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