Peer review of: Caveolin-1-mediated sphingolipid oncometabolism underlies a metabolic vulnerability of (2020)


 
 

Reviewers' comments: 

 

Reviewer #1 (Remarks to the Author): 

 

The revisions to the manuscript have enhanced the clarity and quality of the manuscript text and key 
figures. The critical amendments I requested to the clinical descriptors are now accurate and there is 
greater detail about the key experimental and analysis details that were previously missing or 
incomplete. The inclusion of quantitative data for the animal studies is appreciated and markedly 
strengthens this aspect, but a major issue raised by myself and another reviewer remains 
unaddressed- the quantification of data and confirmation of CAV1 modulation in the 
imunofluorescent studies in Figure 4. With relatively few cells being shown in the images, it is 
particularly important to include quantitative data with larger numbers of cells- this is now relatively 
routine for immunofluorescence work thus it is surprising it has not been done to support a major 
conclusion of the manuscript. Regarding CAV-1 detection, despite the western blots now included 
for an independent experiment, given the known heterogeneity of expression on an individual cell 
level in even stably transfected lines, CAV-1 levels in the images for Figure 4 remain an important 
experiment to include to ensure the data and changes are interpreted appropriately. For that 
purpose live cell imaging is not necessary and standard immunofluorescent protocols could be used 
to visualize CAV1 and the other markers included. 

 

Other Comments: 

 

1. The authors have answered the queries regarding the metabolomics analysis of the clinical 
samples used in the study. Some of these issues (patient fasting status, freeze-thawing etc) are 
intrinsic to large clinical cohorts of active surveillance and understandably cannot be revisited by the 
investigators. However for benefit of the readers and interpretation of results compared to other 
cohorts, it would be important to include these details in the materials and methods section of the 
manuscript, not only the rebuttal. 

 

2. Figure 1C is now much clearer. The data for the normalized gene expression should be included as 
supplementary, and the authors could consider expressing the heatmaps data as median rather than 
average values, as the average will be much more strongly influenced by outlier or high abundance 
genes (or both). 

 

Minor comments: 

 

1. For Figure 5B (now Figure 6B), despite some improved labeling, the figure is proportionally far too 
small compared to the other figure panels and is again impossible to read and interpret. 

 

2. Line 350: Figure 5E should be Figure 6E. 

 

 

 

Reviewer #2 (Remarks to the Author): 

 

The authors of the revised manuscript entitled “Cav-1-Mediated Sphingolipid Oncometabolism 
Underlies a Metabolic Vulnerability of Prostate Cancer” have appropriately addressed all questions 
raised by the reviewer. 

 

 

Reviewer #3 (Remarks to the Author): 

 

The authors have provided a fairly thorough and verbose (longer is not always better) response to 
our critiques, arguing away most points. See some minor issues below. I would argue that 
“mitochondria” is a central part of their mechanism (I see the term repeated lots in Figure 7), why is 
a simple validation of actual mitochondrial components in their EVs beyond the scope of this paper? 

 

They propose an interesting and complex mechanism. The link to mitochondria isn’t so strong and 
probably not critical here, so I would suggest backing off some of those aspects. It’s not just 
mitochondria that need turnover. While I think questions remain about some specific details, in my 
view the paper and concept should be published, but their claims need to be kept in check. I am 
specifically referring to the abstract sentence: 

“Our findings demonstrate involvement of this metabolic program in support of vesicle formation 
that facilitates trafficking of ‘damaged’ mitochondrial components from the cell.” 

 

This has not been shown in my view, although they hope this is the mechanism. I would cut or show 
me some “damaged” mitochondrial components and their functional impact. 

Some minor corrections: 

There is a typo (line 350), where we think Figure 5E should be 6E 

For figures 2D/F, using the term “relative abundance” for the axis title would be much better, as 
“area units” is vague. Please explain how these were normalized in the legend for the reader.