過去二十年間，檸檬酸循環內的酵素如：烏頭酸酶、異檸檬酸脫氫酶、琥珀酸脫氫酶和延胡索酸酶基因組的多處突變可能導致癌症的發生，因為在過去他們被認為是抑制腫瘤生長的因子；我們實驗室也發表過關於琥珀酸脫氫酶乙型在肝癌中的表現量如果降低時會引起瓦氏效應導致腫瘤的惡化。然而透過多個生物資訊資料庫顯示，在檸檬酸循環中的琥珀酸脫氫酶丙型(SDHC)在一些癌症中有大量表現的情形，肺癌和乳癌尤其明顯。Cbioportal資料庫顯示在一些癌症中SDHC的DNA拷貝數，相較於一般組織有著10%以上的上升變化量。Oncomine資料庫也顯示SDHC的mRNA表現量與一般組織相比在癌症中的表現量也是大幅增加。Prognoscan資料庫則是顯示當SDHC的過度表現時，病人會有較差的預後。因此本篇研究的目的即是探究SDHC在肺癌與乳癌的不同時期的表現量與病人存活率之間的相關聯性。利用免疫組織化學染色測驗SDHC在二十一位肺腺癌患者的組織切片中之表現量。分析結果顯示在肺腺癌癌症分期晚期時，SDHC在組織內的表現量有增多的情形，與先前的三個生物資料庫的分析結果呈一致性，並且發現在前期的樣本中，出現間質轉移的癌細胞與周圍組織相比會有顯著的SDHC表現，似乎暗示著SDHC的大量表現可能會引起癌細胞的爬行能力增強，進而使癌細胞惡化，為了證實假設，利用shRNA靜默技術，降低SDHC的胞內表現量。結果顯示，當SDHC的表現下降時，細胞的生長、爬行能力和細胞週期皆受到影響，尤其是爬行能力方面，細胞傷口癒合爬行能力與追蹤爬行實驗都有顯著的變慢，暗示著SDHC與爬行能力有關。總結來說，雖然尚未解出SDHC為何在癌細胞中會大量表現，如何影響癌細胞的惡性程度也尚未明瞭，然而透過生物資訊資料庫的分析能使我們更快找到癌細胞內特殊表現的蛋白，進而作為治療之目標。

Succinate dehydrogenase complex subunit C (SDHC) overexpression correlates with poor prognosis in lung and breast cancers

Author： SHANG-TING CHUNG
Advisor：Dr. Wen-Tsan Chang
Department of Biochemistry and Molecular Biology

Summary
In the past two decades the enzymes in the TCAB cycle, aconitase, isocitrate dehydrogenase 1(IDH1), Succinate dehydrogenase (SDH) and Fumarase (FH) has multiple mutation, lead to certain types of cancer, and they were usually considered as tumor suppressors, our lab also established SDHB decreased in human hepatocellular carcinoma accelerates tumor malignancy by inducing the Warburg effect.However, the multiple mega databases shown that succinate dehydrogenase complex subunit C (SDHC) is overexpression in certain types of cancer, especially in lung and breast cancers. Cbioportal database showed DNA copy number of SDHC is increased 10% up in certain cancers than normal tissue. Oncomine database showa significant increase in its mRNA when compared with normal tissue The Prognoscan database also establish the SDHC overexpression correlates with poor survival. The purpose of the present study was to investigate the role of SDHC expression in tumor grade and survival rate in patients with lung and breast cancers. SDHC expression was assayed in 25 lung cancer tissues by immunohistochemical staining (IHC). Multivariate and univariate analyses were performed to determine the association between SDHC expression and prognosis. Although the mechanism how SDHC overexpression effects the tumor is unknown. It seems SDHC overexpression is an important factor in lung adenocarcinoma and breast invasive adenocarcinoma prognosis. SDHC overexpression can be an interesting potential novel biomarker for lung and breast cancers.
Keyword: SDHC, lung cancer, breast cancer, poor prognosis, immunohistochemical staining,shRNA.
Introduction
Succinate dehydrogenase (SDH), also known as succinate-coenzyme Q reductase (SQR), is composed of four subunits (SDHA, SDHB, SDHC, SDHD) and four A complex of cofactors (SDHAF1, SDHAF2, SDHA3, SDHAF4) and embedded in the inner membrane of the mitochondria. The four subunits that make up the succinate dehydrogenase are translated by genes located in the nucleus. SDHA (also known as flavoprotein) has a covalently bonded flavin adenine dinucleotide (FAD). Coenzyme and succinate binding sites; SDHB (also known as iron-sulphur protein) contains three iron-sulfur clusters [2Fe-2S], [4Fe-4S], and [3Fe-4S], and participates in Qualitative binding, oxidation and electron transport chains; SDHC (also known as cybL) and SDHD (also known as cybS) are hydrophobic proteins responsible for binding to the mitochondrial inner membrane and providing binding sites for ubiquinone. Succinate dehydrogenase is involved in both citric acid and electron transport chains oxidizing fumarate to succinate in the citric acid cycle while in the respiratory chain Coenzyme Q, in turn, transmits electrons along with the reduction of ubiquinone .
The Cbioportal database provides a platform for the collection of more than 20 cancer gene studies.Centrally analyzed nucleic acid microarray results, including data on somatic mutations, changes in the number of DNA copies, miRNA expression, and DNA methylation. Here I analyzed the changes in the number of DNA copies of SDHC in general tissues and cancer tissues. To observe the changes in SDHC mRNA between cancer and general tissues, I used the online analysis website Oncomine database) to collect more than 700 data from more than eight studies. Millions of microarray analysis results also make the results more trustworthy.The Human protein atlas database uses more than 24,000 antibodies for immunohistochemical staining of forty-four organs in humans, but in general organ tissues and cancer tissues and organs. A comparison of staining ,I collected in this database is the performance of SDHC in general organizations. Finally, for the association between SDHC performance in cancer and patient outcome, I used the PrognoScan database for analysis. PrognoScan brings together nucleic acid microarray analysis from Gene Expression Omnibus, Array express and other independent laboratories to analyze more than forty cancers with sufficient patient and medical data to more efficiently find new cancer treatment target.

Material and Methods
Through the analysis of the bioinformatics database, we found that the succinate dehydrogenase-type protein in succinate dehydrogenase has a large number of manifestations in lung cancer, and we have previously found succinate dehydrogenase type B in our laboratory. Excessive performance in liver cancer may reduce the degree of dysfunction , and the results of a large number of succinate dehydrogenase-type C proteins are associated with poor prognosis in patients. Therefore, this study on the relationship between lung cancer and succinate dehydrogenase, to explore whether succinate dehydrogenase affects the malignant degree of lung cancer, first use immunohistochemical staining to confirm succinate dehydrogenase type C protein in patients The performance of the sample, using RNA interference technology to inhibit its performance, and observe the growth rate, crawling ability of lung cancer cells and glycolytic capacity, to explore the relationship between SDHC and lung cancer prognosis.

Results and Discussion
The stable inhibition of SDHC may lead to cell migration, growth, and cell cycle. Unlike other SDH subunits, SDHC may play a role in helping cancer cells grow and crawl, leading to lung glands. The prognosis of cancer patients is worse, which suggests that SDHC may be an indicator or target for lung adenocarcinoma surveillance. Through analysis from the database, from DNA to RNA to protein level, it is proved that SDHC is associated with increased lung cancer growth and tumor growth. This research model can be used as a target and prognosis for cancer treatment in the future. Indicators to develop possible treatments.

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