An Overview of Lipid Droplets in Cancer and Cancer Stem Cells
prostaglandin (PG) biosynthetic profiles from endogenous arachidonic acid were determined by capillary gas chromatography-mass spectrometry in matched fresh normal lung (NL) and lung cancer (LC) tissue fragments obtained from 42 individual LC patients at the time of diagnostic thoracotomy. The histological diagnoses represented were squamous cell carcinoma (N = 20), adenocarcinoma (N = 7), small cell carcinoma (N = 4), mixed cell carcinoma (N = 2), bronchioloalveolar cell carcinoma (N = 2), large cell undifferentiated carcinoma (N = 3), bronchial carcinoid (N = 1), and metastatic tumors (N = 3). When PG biosynthesis was determined in NL tissue separately, low mean levels of PGE2 and PGF2 alpha (less than 2 pmol/mg protein/15 min), intermediate levels of PGD2 and 6-keto-PGF1 alpha (6KPGF1 alpha) (2-7 pmol/mg protein/15 min), and high levels of thromboxane B2 (TXB2) (greater than 7 pmol/mg protein/15 min) were observed. There was no particular correlation with cigarette smoking history and PG biosynthesis in NL. When PG production in LC tissue was evaluated separately, high levels of PGE2, PGF2 alpha, and 6KPGF1 alpha as well as TXB2 and low levels of PGD2 were noted. In addition, LC tissue from cigarette smokers demonstrated elevated levels of PGE2, 6KPGF1 alpha, and TXB2 when compared to current nonsmokers with LC (P less than 0.05 in all instances). Simultaneous comparison of PG production in matched LC and NL tissue from individual patients indicated increased biosynthesis of PGE2 and PGF2 alpha and low levels of PGD2 in LC compared to NL tissue (P less than 0.05 in all instances; paired, two-tailed, Student's t test). Individual comparison of PG biosynthesis according to LC histological cell type revealed that PGE2 and PGF2 alpha were consistently elevated in all four common primary LC histological cell types, the only exception being large cell undifferentiated carcinoma. Interestingly, this latter LC histological cell type presented a unique profile with lower levels of PGE2 and PGD2 in LC than in NL tissue (P less than 0.05 in both instances). In addition, the biosynthesis of all 5 PGs studied was consistently higher in primary than metastatic adenocarcinomas of the lung (P less than 0.05 in all instances). No differences were observed in NL and LC tissue for the major LC histological cell types when PGD2, TXB2, or 6KPGF1 alpha biosyntheses were compared. These findings indicate that the profiles of PG biosynthesis in LC and NL tissue from individual patients may differ substantially. These differences may reflect, in part, contributions to the PG biosynthetic profile unique to malignant cells.