KLF6-SV1 overexpression accelerates human and mouse prostate cancer progression and metastasis
Goutham Narla, … , Mark A. Rubin, John A. Martignetti
Goutham Narla, … , Mark A. Rubin, John A. Martignetti
Published July 1, 2008
Citation Information: J Clin Invest. 2008;118(8):2711-2721. https://doi.org/10.1172/JCI34780.
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Research Article Oncology

KLF6-SV1 overexpression accelerates human and mouse prostate cancer progression and metastasis

Abstract

Metastatic prostate cancer (PCa) is one of the leading causes of death from cancer in men. The molecular mechanisms underlying the transition from localized tumor to hormone-refractory metastatic PCa remain largely unknown, and their identification is key for predicting prognosis and targeted therapy. Here we demonstrated that increased expression of a splice variant of the Kruppel-like factor 6 (KLF6) tumor suppressor gene, known as KLF6-SV1, in tumors from men after prostatectomy predicted markedly poorer survival and disease recurrence profiles. Analysis of tumor samples revealed that KLF6-SV1 levels were specifically upregulated in hormone-refractory metastatic PCa. In 2 complementary mouse models of metastatic PCa, KLF6-SV1–overexpressing PCa cells were shown by in vivo and ex vivo bioluminescent imaging to metastasize more rapidly and to disseminate to lymph nodes, bone, and brain more often. Interestingly, while KLF6-SV1 overexpression increased metastasis, it did not affect localized tumor growth. KLF6-SV1 inhibition using RNAi induced spontaneous apoptosis in cultured PCa cell lines and suppressed tumor growth in mice. Together, these findings demonstrate that KLF6-SV1 expression levels in PCa tumors at the time of diagnosis can predict the metastatic behavior of the tumor; thus, KLF-SV1 may represent a novel therapeutic target.

Authors

Goutham Narla, Analisa DiFeo, Yolanda Fernandez, Saravana Dhanasekaran, Fei Huang, Jaya Sangodkar, Eldad Hod, Devin Leake, Scott L. Friedman, Simon J. Hall, Arul M. Chinnaiyan, William L. Gerald, Mark A. Rubin, John A. Martignetti

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Figure 1

Expression of KLF6 and its splice variants in PCa.

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Expression of KLF6 and its splice variants in PCa. (A) RT-PCR of represe...
(A) RT-PCR of representative prostate-derived cDNAs with KLF6-specific primers. N, normal prostate; L, localized PCa; M, metastatic PCa. (B) qRT-PCR analysis of localized and metastatic PCa cDNAs for wild-type KLF6 expression. Metastatic tumors expressed significantly less wild-type KLF6 mRNA compared with localized tumors. **P < 0.001. (C) qRT-PCR of localized and metastatic PCa samples using wild-type KLF6– and KLF6-SV1–specific PCR primers (refs. 14, 15, and our unpublished observations). (D) Increased KLF6-SV1 expression in metastatic PCa. Western blot analysis using a KLF6-SV1–specific monoclonal antibody (ref. 15 and our unpublished observations). Transfected KLF6-SV1 and transfected wild-type KLF6 controls were run on the same gel but were noncontiguous. Tubulin was used as the loading control for all lanes. (E) Left: DNA microarray analysis of PCa demonstrated downregulation of KLF6 mRNA in hormone-refractory metastatic PCa (HR-MET) compared with both noncancerous prostate tissue and localized PCa. NAP, normal adjacent prostate tissue; PCA, localized PCa. Right: Tissue microarray analysis of KLF6 expression using KLF6 monoclonal antibody 2A2. Data points and error bars represent mean KLF6 protein expression and 95% confidence intervals, respectively. (F) Immunohistochemistry of high-density tissue microarray analyses with the KLF6-SV1–specific monoclonal antibody demonstrated marked upregulation of KLF6-SV1 expression in hormone-refractory metastatic PCa compared with naive metastatic PCa, localized PCa, and benign prostate tissue (P < 0.001). Data points and error bars represent mean KLF6-SV1 protein expression and 95% confidence intervals, respectively. (G) Median survival, as measured using biochemical recurrence and assessed by qRT-PCR, in men whose localized prostate tumors expressed high levels of KLF6-SV1 (blue) was 30 mo compared with 80 mo in men with low KLF6-SV1–expressing tumors (P < 0.01).