Regulation of melanoma by the embryonic skin.

Abstract

This report focuses on the regulation of murine melanoma by the embryonic skin. A surgical technique was developed to allow inijection of B16 melanoma cells into the embryo in utero. A significant decrease in incidence of tumors was noted, which correlated with the time of arrival of normally migrating premelanocytes into the skin. Media were conditioned from skin explanted at the time premelanocytes arrive in it; these media inhibited the growth of melanoma cells in vitro. Under optimal conditions the growth of melanoma cells ceased; the cells had altered morphology and failed to proliferate when placed in fresh growth media.The discovery that cancer cells could differentiate into benign cells and tissues (1, 2) and that the process could be modulated (3) led to the concept that direction of differentiation of malignant to benign cells might serve as an alternative to cytotoxic therapy for cancer (4). In 1974 Brinster produced a chimeric mouse by injecting embryonal carcinoma cells into a blastocyst and putting the injected blastocyst into the uterus of a mouse made pseudopregnant (5). Thus, the blastocyst could regulate embryonal carcinoma cells and their progeny so they behaved as apparently normal embryonic cells. Regulation of tumor (6) and colony (7) formation of embryonal carcinoma by the blastocyst was tissue specific in that it was dependent upon close correspondence of the embryonic field (8) and the malignant cells. Further, contact of the cancer cells with trophectoderm in the presence of blastocele fluid was required (9). The problems occasioned by the paucity of trophectodermal cells made further study of the mechanism of embryonic regulation of embryonal carcinoma extremely difficult.Accordingly, other embryonic fields were examined to see if they could regulate tumor or colony formation of their closely related cancers. The neural-stage mouse embryo regulated neuroblastoma cells (10) MATERIALS AND METHODSIn the surgical approach to mouse embryos in utero, C57BL/6 female mice (The Jackson Laboratory) pregnant for 10 or 14 days (day 1 is the day of observation of the mating plug) were anesthetized with 0.4 ml of Avertin injected intraperitoneally. Avertin is composed of 2.5 g of 2,2,2,-tribromoethanol in 5 ml of 2-methyl-2-butanol and 200 ml of distilled water.A midline abdominal incision was made, a uterine horn was exposed, and the skin and viscera were packed out of the operative field with saline-soaked gauze. The animal was placed under a dissecting microscope using the lowest power objectives and x 10 eyepieces. An assistant observed the operative field through a large magnifying glass. A pursestring suture (6-0 silk) was placed in the uterine muscle, and the muscle inside this suture was divided with fine forceps to expose the fetal membranes. When the yolk sac was reached and before herniation of the embryo could occur, tension was placed on the purse-string suture, and a dam was firmly pressed down over the incision and held in place by the assistant. The dam was a piece of wire b...

Reprogramming of melanoma cells by embryonic microenvironments

“…2 and 3). Tumor formation was not detected in any of the analyzed embryos.These observations with human melanoma cells support previous works that suggested the reprogramming of mouse melanoma genome by the embryonic microenvironments during early embryogenesis and organogenesis (Gerschenson et al, 1986;Hochedlinger et al, 2004). Our results with cultured post-implanted mouse embryos confirm also those obtained recently with zebrafish and chick embryos (Lee et al, 2005;Kulesa et al, 2006), what points out the universality of the mechanisms involved in cancer cell reprogramming by embryonic microenvironment.…”

“…The absence of localized tumor growth after 72 hours of in vitro embryo co-culture suggests that malignant phenotype inhibiting factors are active at the gastrulating stage and during early organogenesis. These results complement previous reports of growth regulation of B16 mouse melanoma cells by 10 dpc mouse embryonic skin (Gerschenson et al, 1986). Further research is required to elucidate the final fate of melanoma cells in mammalian embryos and the details of the signaling pathways underlying tumor growth regulation.…”

“…These lines were previously cultured for some passages in vitro, and the resulting animals do develop tumors (Hochedlinger et al, 2004). Other inconveniences include the difficulty of injecting cells in utero into specific places (Gerschenson et al, 1986;Astigiano et al, 2005). Here we present a new approach using post-implanted mouse embryos cultured in vitro to analyze the ability of the embryonic microenvironment to regulate melanoma cell malignant behavior during organogenesis.…”

Microenvironmental regulation of metastasis

“…Mintz and colleagues showed that the microenvironment of a mouse blastocyst not only suppressed the tumorigenicity of teratocarcinoma cells, but that those cells were stably reprogrammed, resulting in normal chimeric mice 18 . Subsequent studies indicated that the embryonic microenvironment is potent in its ability to reprogramme various cancer cells, including metastatic cells, to a less aggressive phenotype [19][20][21][22][23] . Other groups have demonstrated a particularly important role for stromal fibroblasts in modulating the malignant progression of transformed epithelial cells.…”

Influence of the Microenvironment on Melanoma Cell Fate Determination and Phenotype

“…Pierce and colleagues suggested that cancer is a problem of developmental biology; hence, an embryonic microenvironment capable of differentiating a stem cell lineage should be able to reprogram cancers derived from that lineage (16). In support of this concept, implantation of B16 murine melanoma cells into the embryonic skin of a developing mouse during the time of premelanocyte migration was shown to inhibit melanoma tumor formation.…”