Figure 1. Breast cancer biopsies are naturally ¹³C-enriched and nitrogen-rich.

(a) The natural abundance in ¹³C (δ¹³C, vs. V-PDB) and ¹⁵N (δ¹⁵N, vs. air N₂) differentiates control from tumor patient tissue samples (n = 23). One sample pair of healthy (adjacent) and cancerous tissues not characterized for receptors (u and u’, respectively) and three triple negative tumor samples (t) are also shown. (b) Taken as a whole, the change in the ¹³C-abundance (Δδ) in cancerous tissues in tumor/adjacent tissue pairs was significant (P < 0.01, n = 5). (c) ¹³C-abundance (Δδ) was inversely correlated with the total lipid content (r² = 0.48, P < 0.03). (d) Regardless of receptor expression, cancerous tissues had a higher elemental content in N (P < 0.05). In (a,c), each datum is the average of 3 sub-samples. In (d), lower case letters stand for statistical classes, P < 0.05.