雄性素對於前列腺癌細胞水解磷酸調控淋巴管生成因子的訊息傳遞路徑影響之研究

Abstract

賀爾蒙療法用於治療前列腺癌已有四十年之久，但治療一段時間後常因癌細胞對雄性素的刺激不再敏感，而復發成為雄性素非依賴型的癌細胞，這類型的癌細胞具有較強的侵入性、增生能力和較快的惡化速度使病人在復發後有嚴重的症狀。目前的研究對於這種癌細胞的轉型機制並不清楚。在臨床的研究上發現，淋巴管新生和淋巴轉移的現象對於癌細胞的惡化扮演着重要的腳色。其中，血管內皮細胞生長因子-C (VEGF-C) 被認為是調控此機制的重要因素。近期的研究顯示雄性素在前列腺癌細胞中可以負向調控 VEGF-C 的表現。此外，大鼠前列腺及人類前列腺癌細胞株的生長在没有雄性素的環境中，可以在細胞內產生活性氧化物(ROS)。本實驗室先前的研究結果顯示，在前列腺癌細胞株 PC-3 中，水解磷酸酯(LPA) 可以藉由刺激 ROS 的產生而促進 VEGF-C 的表現。本論文嘗試在不同種類的前列腺癌細胞內，以雄性素促進劑與拮抗劑對LPA、ROS、VEGF-C 路徑的影響，了解雄性素在前列腺癌細胞的惡化過程中所扮演的角色。在 PC-3 細胞內，即時定量聚合酶連鎖反應的分析顯示 LPA 刺激 VEGF-C 的表現會随着時間有不同的表現。此外，加入不同的雄性素促進劑可以有效地降低 LPA 刺激 VEGF-C 的表現。相反地，加入雄性素拮抗劑則可以明顯地促進 VEGF-C 的表現。另一方面，利用流式細胞儀檢測 LPA 刺激細胞產生的 ROS 量，會因為加入雄性素促進劑而下降，而加入雄性素拮抗劑則有相反的效果。因此，在我的研究中顯示 LPA 透過ROS 而產生VEGF-C 的機轉會受到生長環境中的雄性素調控。經本實驗結果，我們推論前列腺癌細胞藉由LPA、ROS、VEGF-C、淋巴管新生和淋巴轉移的這條路徑，可能會與雄性素的訊息傳遞路徑互相影響。此研究可為預防前列腺癌細胞產生惡化提供一項新的治療方針。

Androgen deprivation therapy has been used to treat prostate cancer for over 40 years; however, it often recurs with severe adverse effects such as increase of invasion, proliferation, and malignancy of tumor due to its insensitivity to androgen stimulation. The molecular mechanisms of this gradual transition are not clearly understood. Clinical evidences suggest that lymphangiogenesis and lymphatic metastasis, which are significantly affected by vascular endothelial growth factor (VEGF-C), are important processes during the malignant progression of prostate cancer. Recent reports indicate that androgen negatively regulates VEGF-C in prostate cancer cell lines. Additionally, androgen deprivation leads to intracellular reactive oxygen species (ROS) generation in rat prostate and a human androgen-dependent prostate cancer cell line LNCaP. Furthermore, our previous studies demonstrated that lysophosphatidic acid (LPA) induces the expression of VEGF-C through ROS generation in PC-3 cells, a human androgen-independent prostate cancer cell line. Therefore, we attempt to investigate the roles of androgen in the malignance process by studying its effects on LPA-induced VEGF-C expression through ROS generation in different prostate cancer cells. Real-time PCR analysis proved that LPA-triggered VEGF-C expression is time-dependent in prostate cancer cells. In addition, our results showed that androgen agonists, mibolerone and dihydrotestosterone (DHT), decrease LPA-induced VEGF-C expression. In contrast, androgen antagonist, bicalutamide, enhances LPA- induced VEGF-C expression. Flow cytometric analysis revealed that LPA-triggered ROS generation was decreased by mibolerone and DHT and enhanced by bicalutamide in prostate cancer cell lines. In summary, we demonstrated that androgen negatively regulates LPA-induced VEGF-C expression through ROS generation in human prostate cancer cell lines. We may infer that LPA induced VEGF-C through ROS crosstalk with androgen signaling. These findings potentially lead to develop a new strategy for preventing lymphatic metastasis of prostate cancer.