探討褪黑激素抑制紓癌特抗藥性腎癌細胞轉移之分子機轉

腎細胞癌(Renal cell carcinoma)為常見的腎臟惡性腫瘤，早期診斷者具有良好的預後，惟一旦發生轉移，治療成效顯著下降。標靶藥物為晚期腎細胞癌之主流治療手段，標靶藥物有效針對腫瘤血管新生與抑制癌細胞增生，其中小分子多重酪胺酸激酶抑制劑舒尼替尼（Sunitinib）廣泛應用於臨床。然而，許多患者在治療後出現藥物抗性，限制其療效。近年研究指出，內生性荷爾蒙褪黑激素（melatonin）具有抗腫瘤潛力，但目前未有研究闡述其對舒尼替尼抗藥性(Sunitinib resistance, SR)腎癌之抗癌效果及分子機制。我們初步研究成功建立舒尼替尼抗藥性(A498-SR、Caki-1-SR)細胞株，且證實SR-RCC細胞株增生和轉移能力較強。因此，本研究使用褪黑激素處理SR細胞株，褪黑激素有效抑制SR-RCC增生、轉移能力，也會造成活化內質網壓力及GRP78蛋白表現，可能是透過p38-MAPK調控。接著透過蛋白酶生物晶片篩選受SR-RCC與褪黑激素調控水解蛋白，並以西方墨點法驗證分析發現轉移相關蛋白酶Cathepsin D (CTSD)於SR細胞株大量表現，經褪黑激素作用後表現下降。綜合上述結果，褪黑激素透過抑制p38-MAPK造成內質網壓力路徑活化調控CTSD影響SR-RCC轉移能力，代表褪黑激素對治療SR-RCC轉移深具潛力，期許後續利用褪黑激素合併標靶藥物，為治療腎細胞癌帶來新穎的治療策略。

Renal cell carcinoma (RCC) is a common malignant tumor of the kidney. Patients diagnosed at an early stage generally have a favorable prognosis. However, once metastasis occurs, treatment efficacy declines significantly.Targeted therapy is the mainstay treatment for advanced RCC, effectively inhibiting tumor angiogenesis and cancer cell proliferation. Among these agents, sunitinib, a small-molecule multi-targeted tyrosine kinase inhibitor, is widely used in clinical practice. However, many patients develop drug resistance after treatment, which limits its therapeutic efficacy. Recent studies have indicated that the endogenous hormone melatonin possesses anti-tumor potential. Nevertheless, no studies have yet elucidated its anti-cancer effects and molecular mechanisms in sunitinib-resistant (SR) RCC. In this study, we established sunitinib-resistant RCC cell lines (A498-SR and Caki-1-SR) that exhibited increased proliferation and metastatic potential. Treatment with melatonin significantly inhibited these malignant traits, induced endoplasmic reticulum (ER) stress, and upregulated GRP78 expression, likely through inhibition of the p38-MAPK pathway. Protease array and Western blot analyses identified the metastasis-associated protease Cathepsin D (CTSD) as being overexpressed in SR cells, with its expression markedly reduced following melatonin treatment. These findings suggest that melatonin suppresses SR-RCC metastasis by modulating ER stress via p38-MAPK inhibition and downregulating CTSD, indicating its potential as a therapeutic agent, especially when combined with targeted therapies.