SPINK1 as a plasma marker for tumor hypoxia and a therapeutic target for radiosensitization
Tatsuya Suwa, … , Ester M. Hammond, Hiroshi Harada
Tatsuya Suwa, … , Ester M. Hammond, Hiroshi Harada
Published November 8, 2021
Citation Information: JCI Insight. 2021;6(21):e148135. https://doi.org/10.1172/jci.insight.148135.
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Research Article Cell biology Oncology Article has an altmetric score of 6

SPINK1 as a plasma marker for tumor hypoxia and a therapeutic target for radiosensitization

Abstract

Hypoxia is associated with tumor radioresistance; therefore, a predictive marker for tumor hypoxia and a rational target to overcome it have been sought to realize personalized radiotherapy. Here, we show that serine protease inhibitor Kazal type I (SPINK1) meets these 2 criteria. SPINK1 expression was induced upon hypoxia (O2 < 0.1%) at the transcription initiation level in a HIF-dependent manner, causing an increase in secreted SPINK1 levels. SPINK1 proteins were detected both within and around hypoxic regions of xenografted and clinical tumor tissues, and their plasma levels increased in response to decreased oxygen supply to xenografts. Secreted SPINK1 proteins enhanced radioresistance of cancer cells even under normoxic conditions in EGFR-dependent and nuclear factor erythroid 2–related factor 2–dependent (Nrf2-dependent) manners and accelerated tumor growth after radiotherapy. An anti-SPINK1 neutralizing antibody exhibited a radiosensitizing effect. These results suggest that SPINK1 secreted from hypoxic cells protects the surrounding and relatively oxygenated cancer cells from radiation in a paracrine manner, justifying the use of SPINK1 as a target for radiosensitization and a plasma marker for predicting tumor hypoxia.

Authors

Tatsuya Suwa, Minoru Kobayashi, Yukari Shirai, Jin-Min Nam, Yoshiaki Tabuchi, Norihiko Takeda, Shusuke Akamatsu, Osamu Ogawa, Takashi Mizowaki, Ester M. Hammond, Hiroshi Harada

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Figure 6

SPINK1 decreases radiation-induced DNA damage and enhances radioresistance of cancer cells in a NRF2-dependent manner.

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SPINK1 decreases radiation-induced DNA damage and enhances radioresistan...
(A and B) Four days after being transfected with either pcDNA4/SPINK1 (SPINK1) or its EV, DU145 cells were subjected to qPCR. (C–I) HeLa/scramble cells and HeLa/shSPINK1-1, HeLa/shSPINK1-2, and HeLa/shSPINK1-3 cells were cultured under severe hypoxic conditions (O2 < 0.1%) for 48 hours, irradiated with 0 (C, D, and I) or 4 (E–I) Gy of γ-rays and subjected to qPCR (C–H) or the DCFDA cellular ROS assay (I). Cells were irradiated in the presence or absence of the EGFR-I III (G and H). (J) DU145 cells were irradiated with γ-rays in the presence or absence of 100 ng/mL rSPINK1 in combination with DMSO or 2 μM ML385 and subjected to the colorimetric cell viability assay. Data are represented as mean ± SD (n = 3 in A–J). Two-tailed Student’s t test (A, B, and J). One-way ANOVA with Dunnett’s test (C–I). *P < 0.05, **P < 0.01, ***P < 0.001. SPINK1, serine peptidase inhibitor Kazal type 1; EV, empty vector; DCFDA, dichlorodihydrofluorescein diacetate; EGFR-I III, EGFR Inhibitor III.