Dear Wenyu,

This is a great question, and I can imagine will bring some interesting discussion. Detection of pH within cells is a relatively easy process through the use of specific pharmaco reagents that use pH reactive dyes, and also directly through the use of electrophysiology. The technology is certainly out there to measure pH of cells and of intra-cellular compartments.

To be totally honest I dont know if the pH of endosomes varies between tumor cells and normal cells, as I have not tested this or read about this. Considering tumor cells can be either benign or activated that would suggest a change in state of the endomembrane system (system that encompasses endosomes, lysosomes, autophagosomes...etc) between tumor cells. My reasoning is that activity greatly depends on the rate of turnover of the cytoskeleton, the energy required for that turnover, and an excess of available membrane, all of which are interconnected with the endomembrane system.

The endomembrane system itself is an active trafficking process requiring energy, cytoskeleton and membrane. But the processes itself are required to produce excess ATP, free membrane, directional deposition of membrane...etc. The regulation of pH is key as pH change through ion transfer across membranes is a crucial mechanical control over the whole process. Relating this back to tumor cells, I would imagine that pH change occurs faster (possibly due to less regulation or even greater regulation??) to push for faster turnover in other intra-cellular systems. But this would be for an activated tumor cell, what would be the state for benign tumor cells and how does a tumor cell control this change?

As you can see, there are lots of questions that stem from your own. I understand that I havent answered your questions, simply added to them. I apologise if this has added any confusion but this is a great topic for debate and addition of ideas, which I wanted to add to. Thank you for asking your questions, its great to see other researchers asking similar things! I hope there is someone out there who can give you the best answers.

Best regards,

Chris

Dear Christopher，

Thanks a lot for your kind answer. Your answer is great from the Biology subject. This is a good point where we can think about. My background is Material Eng. So I am not sure about whether there is difference. Thanks a lot!

Regards,

Wenyu

In case of cancer of both types, benign or malignant, there is higher rate of cell differentiation (irratic and uncontrolled growth) where the oxygen supply gets lower in comparison to the normal cells. Therefore, the tumor cells undergo anearobic respiration  (as the tumor mass doesn't have capillaries network to receive oxygen from blood) resulting into formation of excess of lactic acid in the cell compartments. This event changes the pH profile of tumor cells (acidic i.e., lower pH) when compared to the normal cells. While in case of aerobic respiration, normal cells produce CO2 and energy and thereby maintaining the pH to normal. Moreover, the temperature also rises due to continuous cell growth and differentiation to liberate energy.    

Dear Santosh,

Thanks for your answer. As you said, we know the pH of the evironment of outside tumor cells is lower than normal cells. But here, we talk about the difference of endosomal pH, not the pH extracellular environment.  Thanks again for your discussion!

Wenyu