Quantitative analysis of autophagy using advanced 3D fluorescence microscopy.

Chun A. Changou, Deanna L. Wolfson, Balpreet Singh Ahluwalia, Richard J. Bold, Hsing Jien Kung, Frank Y S Chuang

Research output: Contribution to journalArticle

Abstract

Prostate cancer is the leading form of malignancies among men in the U.S. While surgery carries a significant risk of impotence and incontinence, traditional chemotherapeutic approaches have been largely unsuccessful. Hormone therapy is effective at early stage, but often fails with the eventual development of hormone-refractory tumors. We have been interested in developing therapeutics targeting specific metabolic deficiency of tumor cells. We recently showed that prostate tumor cells specifically lack an enzyme (argininosuccinate synthase, or ASS) involved in the synthesis of the amino acid arginine(1). This condition causes the tumor cells to become dependent on exogenous arginine, and they undergo metabolic stress when free arginine is depleted by arginine deiminase (ADI)(1,10). Indeed, we have shown that human prostate cancer cells CWR22Rv1 are effectively killed by ADI with caspase-independent apoptosis and aggressive autophagy (or macroautophagy)(1,2,3). Autophagy is an evolutionarily-conserved process that allows cells to metabolize unwanted proteins by lysosomal breakdown during nutritional starvation(4,5). Although the essential components of this pathway are well-characterized(6,7,8,9), many aspects of the molecular mechanism are still unclear - in particular, what is the role of autophagy in the death-response of prostate cancer cells after ADI treatment? In order to address this question, we required an experimental method to measure the level and extent of autophagic response in cells - and since there are no known molecular markers that can accurately track this process, we chose to develop an imaging-based approach, using quantitative 3D fluorescence microscopy(11,12). Using CWR22Rv1 cells specifically-labeled with fluorescent probes for autophagosomes and lysosomes, we show that 3D image stacks acquired with either widefield deconvolution microscopy (and later, with super-resolution, structured-illumination microscopy) can clearly capture the early stages of autophagy induction. With commercially available digital image analysis applications, we can readily obtain statistical information about autophagosome and lysosome number, size, distribution, and degree of colocalization from any imaged cell. This information allows us to precisely track the progress of autophagy in living cells and enables our continued investigation into the role of autophagy in cancer chemotherapy.

Original languageEnglish (US)
JournalJournal of visualized experiments : JoVE
Issue number75
StatePublished - 2013
Externally publishedYes

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Arginine
Fluorescence microscopy
Autophagy
Fluorescence Microscopy
Cells
Tumors
Chemical analysis
Hormones
Microscopic examination
Argininosuccinate Synthase
Neoplasms
Prostatic Neoplasms
Lysosomes
Chemotherapy
Deconvolution
Cell death
Caspases
Microscopy
Fluorescent Dyes
Refractory materials

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Quantitative analysis of autophagy using advanced 3D fluorescence microscopy. / Changou, Chun A.; Wolfson, Deanna L.; Ahluwalia, Balpreet Singh; Bold, Richard J.; Kung, Hsing Jien; Chuang, Frank Y S.

In: Journal of visualized experiments : JoVE, No. 75, 2013.

Research output: Contribution to journalArticle

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