I like to know the possible markers of metabolism in cancer cells such as in monitoring glycolytic, extracellular acidification and oxygen consumption rates, effected by treatment with an extract.
The easiest one, that does not require practically anything, is to observe the color of culture medium. If it turns yellow after 2-4 days of culture, there is an intense glycolytic metabolism, if cell metabolism is affected by your treatment, you will see the color change. If you want more quantitative data, harvest the medium and measure the pH.