Cellular and Molecular Biology

KSHV infection skews macrophage polarisation towards M2-like/TAM and activates Ire1 α-XBP1 axis up-regulating pro-tumorigenic cytokine release and PD-L1 expression



Kaposi’s Sarcoma Herpesvirus (KSHV) is a gammaherpesvirus strongly linked to human cancer. The virus is also able to induce immune suppression, effect that contributes to onset/progression of the viral-associated malignancies. As KSHV may infect macrophages and these cells abundantly infiltrate Kaposi’s sarcoma lesions, in this study we investigated whether KSHV-infection could affect macrophage polarisation to promote tumorigenesis.


FACS analysis was used to detect macrophage markers and PD-L1 expression. KSHV infection and the molecular pathways activated were investigated by western blot analysis and by qRT-PCR while cytokine release was assessed by Multi-analyte Kit.


We found that KSHV infection reduced macrophage survival and skewed their polarisation towards M2 like/TAM cells, based on the expression of CD163, on the activation of STAT3 and STAT6 pathways and the release of pro-tumorigenic cytokines such as IL-10, VEGF, IL-6 and IL-8. We also found that KSHV triggered Ire1 α-XBP1 axis activation in infected macrophages to increase the release of pro-tumorigenic cytokines and to up-regulate PD-L1 surface expression.


The findings that KSHV infection of macrophages skews their polarisation towards M2/TAM and that activate Ire1 α-XBP1 to increase the release of pro-tumorigenic cytokines and the expression of PD-L1, suggest that manipulation of UPR could be exploited to prevent or improve the treatment of KSHV-associated malignancies.

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Fig. 1: KSHV infects macrophages and skews their phenotype towards an M2 phenotype.
Fig. 2: KSHV infection promotes the release of pro-tumorigenic cytokines.
Fig. 3: KSHV infection activates STAT3 and STAT6 in macrophages.
Fig. 4: KSHV activates UPR and up-regulates PD-L1 on KSHV- infected macrophages.
Fig. 5: The Ire1α/XBP1 axis interferes with the pro-tumorigenic cytokines release and PD-L1 expression of KSHV-infected macrophages.


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We thank Dr. G. Girelli (Blood bank, Sapienza University of Rome) and Dr G. Mandarello and Dr R. Gasbarri (Immunohematology and Transfusion Service, Belcolle Hospital, Viterbo) for providing buffy coats. We also thank Alessia Garufi and Micol Di Segni for technical assistance in qRT-PCR experiments.

Author information




M.S.G.M. performed macrophage preparation and FACS analysis. L.F., R.S., N.C., M.S.G.M. performed western blot analysis and analysed the data. M.A.R., M.G., R.G. performed cell culture and Elisa assays. G.D.O. carried out qRT-PCR. M.C., G.D.O. and A.F. discussed the data. M.C. and M.S.G.M. conceived the experiments. M.C. wrote the paper.

Corresponding author

Correspondence to Mara Cirone.

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This research involving human subjects has been performed in accordance with the Declaration of Helsinki and has been approved by the ethic committee of Policlinico Umberto I, Rome, Italy (847/19).

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The datasets generated and/or analysed during the current study are available from the corresponding author upon reasonable request.

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The authors declare no competing interests.

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This work was supported by grants from Istituto Pasteur Italia-Fondazione Cenci Bolognetti, PRIN 2017 (2017K55HLC) and by the Italian Association for Cancer Research (AIRC) Grant (IG 2019 Id.23040).

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Gilardini Montani, M.S., Falcinelli, L., Santarelli, R. et al. KSHV infection skews macrophage polarisation towards M2-like/TAM and activates Ire1 α-XBP1 axis up-regulating pro-tumorigenic cytokine release and PD-L1 expression. Br J Cancer 123, 298–306 (2020). https://doi.org/10.1038/s41416-020-0872-0

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