Beta Iii-Tubulin Is Required For The Tumorigenic Phenotype And Resistance To Anoikis Via The Pten/Akt Signaling Axis In Non-Small Cell Lung Cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA BACKGROUND: Non-small cell lung cancer (NSCLC) has a dismal prognosis and remains the most common cause of cancer death worldwide. Expression of βIII-tubulin, encoded by the TUBB3 gene, is associated with clinical resistance and aggressive disease in NSCLC1. Herein, we interrogated the mechanistic role of βIII-tubulin in regulating the tumorigenic potential of NSCLC. METHODS: Functional studies involved independent clones of NSCLC H460 cells stably expressing shRNA targeting βIII-tubulin, H460 controls stably expressing (non-functional) shRNA and βIII-tubulin rescue clones established in our laboratory2. Differential proteomics was conducted using fluorescence based 2D-DIGE and mass spectrometry. Gene and protein expression performed by qRT-PCR and western blotting respectively. To assess effects on tumor growth and incidence we used metastatic (tail vein) and subcutaneous models of NSCLC. Tumors monitored by CT or Xenogen imaging. RESULTS: Functional and differential proteomics revealed that βIII-tubulin regulates expression of tumor growth- and metastases-associated proteins. In particular, the tumor suppressor maspin, associated with adhesion and metastasis, was differentially regulated by βIII-tubulin. Functionally, βIII-tubulin suppression led to altered cell morphology, increased cell adhesion and increased sensitivity to anoikis. Mechanistically, we identified PTEN and AKT kinase as a key signaling axis mediating anoikis and regulated by βIII-tubulin levels in NSCLC cells. Finally, βIII-tubulin suppression was shown to reduce NSCLC tumor growth and incidence in vivo. Collectively, these data identified βIII-tubulin as a regulator of tumor growth and metastasis through regulation of PTEN and AKT signaling. We conclude that suppressing βIII-tubulin may reduce tumor growth in NSCLC. SIGNIFICANCE: This is the first study to show that silencing βIII-tubulin alters the expression of proteins involved in promoting tumorigenicity and increases sensitivity to anoikis, leading to reduced tumor incidence. Targeting βIII-tubulin could be a promising strategy for inhibiting tumor growth and metastasis in NSCLC. 1 Kavallaris, M. Nature Rev Cancer, 10:194-204, 2010 2 McCarroll et al. Cancer Res 70 :4995-5003, 2010 Citation Format: Joshua A. McCarroll, Pei Pei Gan, Rafael B. Erlich, Marjorie Liu, Tanya Dwarte, Mia C. Akerfeldt, Melissa Chang, Michael S. Shum, Frances Byrne, Maria Kavallaris. βIII-tubulin is required for the tumorigenic phenotype and resistance to anoikis via the PTEN/AKT signaling axis in non-small cell lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2076. doi:10.1158/1538-7445.AM2014-2076