Kallikrein-related peptidase 4 (KLK4) as a new target toimprove immune intervention in ovarian cancer

卵巢癌免疫干预成功的基本前提是肿瘤有足够的肿瘤抑制淋巴细胞的渗透。它们的趋化募集是由CXCR3趋化因子受体及其配体CXCL9、CXCL10和CXCL11介导的。我们已经证明，这些CXCR3趋化因子在卵巢癌中的高表达与肿瘤浸润性淋巴细胞的数量增加和总存活率的提高有关。为了逃避免疫系统，肿瘤细胞可以产生能够裂解和灭活肿瘤内趋化因子的蛋白酶。与我们的国际合作伙伴一起，我们将CXCL9确定为激肽释放酶相关肽酶4(KLK4)的高亲和力靶点。此外，已知CXCR3配体在人卵巢癌中以裂解趋化因子的形式存在。由于KLK4在人卵巢癌中过表达，但生理上仅在发育中的牙齿和前列腺中表达，我们推测KLK4可能代表着一个非常特异的药物靶点，通过提高活跃的CXCR3趋化因子在肿瘤内的浓度来改善卵巢癌的免疫治疗(例如，检查点抑制)。为了验证这一假设，我们将进一步表征KLK4和其他KLK对CXCL9和其他CXCR3趋化因子的切割。主要的焦点是这些裂解对趋化能力的影响。在卵巢癌同基因小鼠模型中，我们接下来将研究KLK4在肿瘤细胞中的过度表达或敲除对淋巴细胞渗透、肿瘤生长和转移的影响。此外，我们将探索免疫系统，特别是CXCR3受体与观察到的效果的相关性。通过使用已建立的KLK4抑制剂，我们可以进一步模拟抗KLK4治疗及其对肿瘤生长和免疫干预的影响。在对一大批人卵巢癌的回顾分析中，我们最终将检验KLK4的表达水平是否与卵巢癌中肿瘤浸润性淋巴细胞的数量和生存时间呈负相关。该结果旨在首次揭示KLK4在实体恶性肿瘤中的免疫调节功能，并将其定义为改善卵巢癌免疫干预的新治疗靶点。

The fundamental prerequisite for a successful immune intervention in ovarian cancer is a sufficient infiltration of the tumor with tumor-suppressive lymphocytes. Their chemotactic recruitment is mediated by the CXCR3 chemokine receptor and its ligands CXCL9, CXCL10 and CXCL11. We have already shown that a high expression of these CXCR3 chemokines in ovarian cancer is associated with a high number of tumor-infiltrating lymphocytes and an improved overall survival. In order to evade the immune system, tumor cells can produce proteases capable of cleaving and inactivating intratumoral chemokines. Together with our international collaboration partners we have identified CXCL9 as a high-affinity target for kallikrein-related peptidase 4 (KLK4). Moreover, it is known that CXCR3 ligands are present as cleaved chemokines in human ovarian cancer. As KLK4 is overexpressed in human ovarian cancer, but physiologically only expressed in developing teeth and the prostate, we postulate that KLK4 may represent a very specific pharmacological target to improve immunotherapy (e.g. checkpoint inhibition) in ovarian cancer by enhancing the intratumoral concentrations of active CXCR3 chemokines.To test this hypothesis we will further characterize the cleavage of CXCL9 and the other CXCR3 chemokines by KLK4 and also other KLKs. The main focus is the impact of these cleavages on the chemotactic capacity. In a syngeneic mouse model of ovarian cancer, we will next study the effect of KLK4 overexpression or knockout in the tumor cells on lymphocytic infiltration, tumor growth and metastasis. Moreover, we will explore the relevance of the immune system in general, and of the CXCR3 receptor in particular, for the observed effects. By using established KLK4 inhibitors, we can furthermore simulate an anti-KLK4 therapy and its impact on tumor growth and immune intervention. In a retrospective analysis of a large cohort of human ovarian cancers, we will finally test, if KLK4 expression levels are inversely associated with the number of tumor-infiltrating lymphocytes and survival in human ovarian cancer.The results are intended to delineate, for the first time, immunomodulatory functions of KLK4 in solid malignancies and to define it as a new therapeutic target to improve immune intervention in ovarian cancer.