@haidut @Amazoniac @Mauritio Here's something unexpected in breast tumors,
EDIT: its in HER2-enriched breast cancer , so showing nuance between cancers here
using acetazolamide (most potent carbonic anhydrase inhibitor) surprisingly they said it caused tumors to grow. even though tumor pH lowered, and lactate lowered
https://breast-cancer-research.biomedcentral.com/articles/10.1186/s13058-023-01644-1#Sec16
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so the beneficial Apoptosis effect you'd usually see happen in hypoxic cancered cells from the lower pH is hindered / prevented by another effect?
It didnt raise proliferation markers, didnt raise vessel growth,
The density of macrophages is high, T cells moderate, and B cells low; yet overall the abundance of these cell types is reduced by around half in breast cancer tissue from mice treated with acetazolamide compared to vehicle
so by the looks of it the lowered immune cell infiltration prevented the pro apoptosis effect
the extracellular carbonic anhydrases positively predict patient survival in HER2/ErbB2-enriched breast cancer
These observations suggest that carbonic anhydrases—likely via their ability to elevate tumor pHo (Figs. 6 and 8A)—provide an immune-stimulatory input that improves survival of patients with HER2-enriched breast cancer characterized by a weak immune response.
In contrast to HER2-enriched breast cancer, the association between extracellular carbonic anhydrase expression and patient survival in Basal-like breast cancer is seemingly unaffected by tumor inflammation
https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2023.1268421/full Acidification of intracellular pH in MM tumor cells overcomes resistance to hypoxia-mediated apoptosis in vitro and in vivo
Hypoxia-mediated apoptosis of MM cells is correlated with acidic intracellular pHi (less than < 6.6) that is dependent on HIF activity. a carbonic anhydrase inhibitor (acetazolamide), and an NHE-1 inhibitor (amiloride) acidified the pHi and lead to cell death.
In contrast, treatment of cells with an alkalization agent, Na-lactate, rescued these cells by increasing the pHi (pH > 6.6). Finally, treatment of mice with acetazolamide decreased cell growth in the tumor nodules.
{{interestingly just 40 MICROgrams/kg i.p was used to slow tumor growth there)
So this approach should be effective in cancers not characterised by weak immune response , but for those that are, its detrimental to lower pH , (at least without added ph independent immune stimulus overcoming its inhibition , if possible)
(or maybe need to really drive the pH down lower to hit <6.6 ,
so no half measures there? but i think the 1st study already would have hit most of the CA IX inhibition/co2 raise with 40mg/kg i.p right?
here 40mg/kg orally inhibited lung tumor growth a little , and drastically lowered metastasis. so whether its a helpful or harmful effect does seem dependant on immune cell characteristics (otherwise if it worked at this dose here, it shouldnt have raised growth in the other) http://www.chinaphar.com/article/view/7735/8235