Correction: Kallifatidis, G. et al. The Marine Natural Product Manzamine A Targets Vacuolar ATPases and Inhibits Autophagy in Pancreatic Cancer Cells. Mar. Drugs 2013, 11, 3500–3516

We found two errors in our previous published paper [1]. Figure 4A has a mistake in the units in the labels, where it shows mM instead of micromolar (μM). A correctly labeled Figure 4A ensues. In Figure 2 and Figure 4, the size bar scale is micrometers (μm). We apologize for the inconvenience caused to our readers.

Figure 2. Manzamine A affects vacuolar morphology and acidification in yeast, similar to bafilomycin. (A) Vacuolar morphology analysis using Vph1-GFP (a v-ATPase V0 domain) as marker. DMSO treated cells showed clusters of small vacuoles. In bafilomycin A1 treated cells one large vacuole was detected in almost all cells. Manzamine A treated cells displayed a few enlarged vacuoles similar to the situation observed in bafilomycin A1 treated cells. (B) Vacuolar acidification analysis using LysoSensor Green as marker. DMSO treated cells show staining of the vacuolar membranes. Treatment of cells with bafilomycin A1 or manzamine A results in abolishment of detectable vacuolar staining. Size bar represents 5 µm.

Figure 2. Manzamine A affects vacuolar morphology and acidification in yeast, similar to bafilomycin. (A) Vacuolar morphology analysis using Vph1-GFP (a v-ATPase V0 domain) as marker. DMSO treated cells showed clusters of small vacuoles. In bafilomycin A1 treated cells one large vacuole was detected in almost all cells. Manzamine A treated cells displayed a few enlarged vacuoles similar to the situation observed in bafilomycin A1 treated cells. (B) Vacuolar acidification analysis using LysoSensor Green as marker. DMSO treated cells show staining of the vacuolar membranes. Treatment of cells with bafilomycin A1 or manzamine A results in abolishment of detectable vacuolar staining. Size bar represents 5 µm.

Figure 4. Manzamine A increases acidity in pancreatic cancer cells and non-malignant Vero cells. (A) AsPC-1, PANC-1, BxPC-3 and MIA PaCa-2 pancreatic cancer cells, as well as non-malignant Vero cells were treated with 2.5, 5, or 10 μM manzamine A or methanol (vehicle control). Twenty-four hours later cells were stained with Lysosensor green and analyzed by flow cytometry. Numbers in histograms indicate percentage (%) of cells with increased fluorescence intensity compared to vehicle control treated cells. One representative experiment out of three is shown. (B) AsPC-1 cells were treated for 2 h with 10 µM manzamine A or 300 nM bafilomycin A1 alone or in combination. Following treatment, cells were stained by Lysosensor green pH indicator followed by detection of acidic lysosomes by immunofluorescence microscopy at a magnification of 60×. One representative experiment out of three is shown. Size bar represents 150 µm in the main figures and 50 µm in the inserts.

Figure 4. Manzamine A increases acidity in pancreatic cancer cells and non-malignant Vero cells. (A) AsPC-1, PANC-1, BxPC-3 and MIA PaCa-2 pancreatic cancer cells, as well as non-malignant Vero cells were treated with 2.5, 5, or 10 μM manzamine A or methanol (vehicle control). Twenty-four hours later cells were stained with Lysosensor green and analyzed by flow cytometry. Numbers in histograms indicate percentage (%) of cells with increased fluorescence intensity compared to vehicle control treated cells. One representative experiment out of three is shown. (B) AsPC-1 cells were treated for 2 h with 10 µM manzamine A or 300 nM bafilomycin A1 alone or in combination. Following treatment, cells were stained by Lysosensor green pH indicator followed by detection of acidic lysosomes by immunofluorescence microscopy at a magnification of 60×. One representative experiment out of three is shown. Size bar represents 150 µm in the main figures and 50 µm in the inserts.