Pancreatic Tumor Microenvironment Factor Promotes Cancer Stemness via SPP1-CD44 Axis.

Tumor-microenvironment factors and cancer stem cells (CSCs) play a critical role in the aggressiveness of pancreatic cancer (PC). However, the degree to which tumor-microenvironment factors promote stemness remains unexplored. Here, we examined whether cancer-associated fibroblasts (CAFs) promote CSC features in PC.

PC cells were treated long-term (30, 60, and 90 days) with conditioned media (CM)-derived from normal human fibroblasts (NFs) and CAFs. The stemness features of tumorsphere formation and stemness populations, along with CSCs markers, were analyzed using 2-dimensional and 3-dimensional sodium alginate bead-based co-culture models. Immunohistochemistry and immunofluorescence staining were performed for CSCs and fibroblast markers in autochthonous Kras<sup>G12D/+</sup>; Trp53<sup>R172H/+</sup>; Pdx1-Cre mice and human pancreatic tumors. Polymerase chain reaction array and gene knockdown were performed to identify the mechanism of stemness enrichment.

Long-term treatment of PC cells with CAF-CM enriched stemness, as indicated by significantly higher CD44<sup>+</sup>, ALDH<sup>+</sup>, and AF<sup>+</sup> populations in PC cells. Increased tumorsphere formation and elevated CSC, self-renewal, and drug-resistance markers in CAF-CM-treated PC cells were observed. In addition, CAFs co-cultured with PC cells in the 3-dimensional model showed a substantial increase in stemness features. CD44 and α-smooth muscle actin were positively correlated and their expressions progressively increased from the early to late stages of Kras<sup>G12D/+</sup>; Trp53<sup>R172H/+</sup>; Pdx1-Cre mouse and human pancreatic tumors. Osteopontin/secreted phosphoprotein 1 was identified as the top differentially overexpressed gene in CAF-CM-treated PC cells and knockdown of osteopontin/secreted phosphoprotein 1 significantly reduced stemness characteristics in CAF-CM-treated PC cells.

Our data uncovered novel insight into the interplay between CAF and enrichment of stemness population through the osteopontin/secreted phosphoprotein 1-CD44 axis in PC.

Batra SK, Gautam SK, Grabow CE, Jain M, Josh L, Karmakar S, Kumar S, Lakshmanan I, Lele SM, Leon F, Ly QP, Mallya K, Myers MS, Nallasamy P, Nimmakayala RK, Ponnusamy MP, Rachagani S, Seshacharyulu P, Zhang C


Gastroenterology, 2021, 161 (6)

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