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Inhibition of STAT3 augments antitumor efficacy of anti-CTLA-4 treatment against prostate cancer

Witt, Kristina ; Evans-Axelsson, Susan LU orcid ; Lundqvist, Andreas ; Johansson, Martin LU ; Bjartell, Anders LU and Hellsten, Rebecka LU (2021) In Cancer Immunology, Immunotherapy 70(11). p.3155-3166
Abstract

There is an urgent need for new treatment options in metastatic drug-resistant prostate cancer. Combining immunotherapy with other targeted therapies may be an effective strategy for advanced prostate cancer. In the present study, we sought to investigate to enhance the efficacy of anti-CTLA-4 therapy against prostate cancer by the combination with STAT3 inhibition. Male C57BL6 mice were subcutaneously inoculated with the murine prostate cancer cell line RM-1. Tumor progression was monitored following treatment with vehicle, the small molecule STAT3 inhibitor GPB730, anti-CTLA-4 or GPB730 + anti-CTLA-4. Treatment with anti-CTLA-4 or anti-CTLA-4 + GPB730 significantly inhibited tumor growth and enhanced survival compared to vehicle.... (More)

There is an urgent need for new treatment options in metastatic drug-resistant prostate cancer. Combining immunotherapy with other targeted therapies may be an effective strategy for advanced prostate cancer. In the present study, we sought to investigate to enhance the efficacy of anti-CTLA-4 therapy against prostate cancer by the combination with STAT3 inhibition. Male C57BL6 mice were subcutaneously inoculated with the murine prostate cancer cell line RM-1. Tumor progression was monitored following treatment with vehicle, the small molecule STAT3 inhibitor GPB730, anti-CTLA-4 or GPB730 + anti-CTLA-4. Treatment with anti-CTLA-4 or anti-CTLA-4 + GPB730 significantly inhibited tumor growth and enhanced survival compared to vehicle. Combining anti-CTLA-4 treatment with GPB730 resulted in a significantly prolonged survival compared to anti-CTLA-4 alone. GPB730 significantly increased infiltration of CD45 + cells in tumors of anti-CTLA-4-treated mice compared to anti-CTLA-4 alone. The levels of tumor-infiltrating Tregs were significantly decreased and the CD8:Treg ratio significantly increased by GPB730 treatment in combination with anti-CTLA-4 compared to anti-CTLA-4 alone. Immunohistochemical analysis showed a significant increase in CD45-positive cells in anti-CTLA-4 and anti-CTLA-4 + GPB730-treated tumors compared to vehicle or GPB730 monotherapy. Plasma levels of IL10 were significantly increased by anti-CTLA-4 compared to vehicle but no increase was observed when combining anti-CTLA-4 with GPB730. In conclusion, STAT3 inhibition by GPB730 enhances the antitumoral activity of anti-CTLA-4 and decreases the intratumoral Treg frequency in a prostate cancer mouse model. These results support the combination of STAT3 inhibition with anti-CTLA-4 therapy to increase clinical responses in patients with prostate cancer.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Anti-CTLA-4, Immunotherapy, Prostate cancer, Small molecule inhibitor, STAT3, STAT3 inhibitors, Treg
in
Cancer Immunology, Immunotherapy
volume
70
issue
11
pages
3155 - 3166
publisher
Springer
external identifiers
  • scopus:85103939253
  • pmid:33786638
ISSN
0340-7004
DOI
10.1007/s00262-021-02915-6
language
English
LU publication?
yes
id
b47fae9e-2172-45b5-b90e-1a692f33d288
date added to LUP
2021-04-21 08:36:43
date last changed
2024-04-20 05:07:04
@article{b47fae9e-2172-45b5-b90e-1a692f33d288,
  abstract     = {{<p>There is an urgent need for new treatment options in metastatic drug-resistant prostate cancer. Combining immunotherapy with other targeted therapies may be an effective strategy for advanced prostate cancer. In the present study, we sought to investigate to enhance the efficacy of anti-CTLA-4 therapy against prostate cancer by the combination with STAT3 inhibition. Male C57BL6 mice were subcutaneously inoculated with the murine prostate cancer cell line RM-1. Tumor progression was monitored following treatment with vehicle, the small molecule STAT3 inhibitor GPB730, anti-CTLA-4 or GPB730 + anti-CTLA-4. Treatment with anti-CTLA-4 or anti-CTLA-4 + GPB730 significantly inhibited tumor growth and enhanced survival compared to vehicle. Combining anti-CTLA-4 treatment with GPB730 resulted in a significantly prolonged survival compared to anti-CTLA-4 alone. GPB730 significantly increased infiltration of CD45 + cells in tumors of anti-CTLA-4-treated mice compared to anti-CTLA-4 alone. The levels of tumor-infiltrating Tregs were significantly decreased and the CD8:Treg ratio significantly increased by GPB730 treatment in combination with anti-CTLA-4 compared to anti-CTLA-4 alone. Immunohistochemical analysis showed a significant increase in CD45-positive cells in anti-CTLA-4 and anti-CTLA-4 + GPB730-treated tumors compared to vehicle or GPB730 monotherapy. Plasma levels of IL10 were significantly increased by anti-CTLA-4 compared to vehicle but no increase was observed when combining anti-CTLA-4 with GPB730. In conclusion, STAT3 inhibition by GPB730 enhances the antitumoral activity of anti-CTLA-4 and decreases the intratumoral Treg frequency in a prostate cancer mouse model. These results support the combination of STAT3 inhibition with anti-CTLA-4 therapy to increase clinical responses in patients with prostate cancer.</p>}},
  author       = {{Witt, Kristina and Evans-Axelsson, Susan and Lundqvist, Andreas and Johansson, Martin and Bjartell, Anders and Hellsten, Rebecka}},
  issn         = {{0340-7004}},
  keywords     = {{Anti-CTLA-4; Immunotherapy; Prostate cancer; Small molecule inhibitor; STAT3; STAT3 inhibitors; Treg}},
  language     = {{eng}},
  number       = {{11}},
  pages        = {{3155--3166}},
  publisher    = {{Springer}},
  series       = {{Cancer Immunology, Immunotherapy}},
  title        = {{Inhibition of STAT3 augments antitumor efficacy of anti-CTLA-4 treatment against prostate cancer}},
  url          = {{http://dx.doi.org/10.1007/s00262-021-02915-6}},
  doi          = {{10.1007/s00262-021-02915-6}},
  volume       = {{70}},
  year         = {{2021}},
}