Host-Derived Pericytes and Sca-1⁺Cells Predominate in the MART-1⁻Stroma Fraction of Experimentally Induced Melanoma

Abstract

Identification of cell types in tumor-associated stroma that are involved in the development of melanoma is hampered by their heterogeneity. The authors used flow cytometry and immunohistochemistry to demonstrate that anti–MART-1 antibodies can discriminate between melanoma and stroma cells. They investigated the cellular composition of the MART-1−, non-hematopoietic melanoma-associated stroma, finding it consisted mainly of Sca-1+ and CD146+ cells. These cell types were also observed in the skin and muscle adjacent to developing melanomas. The Sca-1+ cell population was observed distributed in the epidermis, hair follicle bulges, and tumor capsule. The CD146+ population was found distributed within the tumor, mainly associated with blood vessels in a perivascular location. In addition to a perivascular distribution, CD146+ cells expressed α-smooth muscle actin, lacked expression of endothelial markers CD31 and CD34, and were therefore identified as pericytes. Pericytes were found to be associated with CD31+ endothelial cells; however, some pericytes were also observed associated with CD31−, MART-1+ B16 melanoma cells that appeared to form blood vessel structures. Furthermore, the authors observed extensive nuclear expression of HIF-1α in melanoma and stroma cells, suggesting hypoxia is an important factor associated with the melanoma microenvironment and vascularization. The results suggest that pericytes and Sca-1+ stroma cells are important contributors to melanoma development.

Putative role of HIF transcriptional activity in melanocytes and melanoma biology

“…In addition, overexpression of HIF-1α promoted soft colony formation and invasion through Matrigel. Moreover, in a separate study, it was observed that increased HIF-1α expression was present not only in the melanoma cells but also in melanoma-associated stromal cells, including pericytes 42 . Finally, increased expression of HIF-1α and HIF-2α was found to be correlated with VEGF expression 43 .…”

Hypoxia‐inducing factors as master regulators of stemness properties and altered metabolism of cancer‐ and metastasis‐initiating cells

“…Moreover, tumour hypoxia has also been associated with enhanced expression of HIFs, lactate dehydrogenase 5 and autophagy‐related proteins, including beclin‐1 and light chain 3A (LC3A), in hypoxic melanoma cells that may promote anaerobic glycolysis and extensive autophagy activity and contribute to their survival under oxygen and nutrient deprivation . On the other hand, high level of HIF‐1α has also been detected in melanoma cells expressing melanoma antigen recognized by T cells‐1 MART‐1 + found in perivascular regions within tumour as well as MART‐1 − non‐haematopoietic melanoma‐associated stromal cells, including CD146 + pericytes associated with CD31 + endothelial cells and Sca‐1 + stromal cells in a mouse model of melanoma . This suggests that stromal cells and melanoma cells, which can form functional vessel‐like structures by vasculogenic mimicry, can cooperate for tumour vascularization supporting the interest to co‐target these cells to counteract melanoma development.…”

Genetic Polymorphisms Associated with Hearing Threshold Shift in Subjects during First Encounter with Occupational Impulse Noise

“…In normal cells, nucleolin is associated to the fibrillar components in nucleoli [ 24 ]. Immunocytochemistry labeling protocols were applied to cells seeded in Lab-Tek II 4-well chamber slides (Nalgen Nuc) [ 25 ]. After incubation, wells were washed from residual culture media with Dublecco’s Phosphate Buffered Saline (DPBS) and Tris-Buffered Saline solution with 0.1% Tween 20 (TBS-T), then fixed in 4% paraformaldehyde in PBS pH 7.2, freshly diluted from 16% paraformaldehyde, for 10 min at RT.…”