A novel growth stimulating activity from BRL-3A cell conditioned medium

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The R- cell line, derived from mouse embryos, has a homozygous disruption of insulin-like growth factor 1 receptor (IGF-IR) genes.
• R- cells exhibit limited growth in serum-free medium (SFM) even with known growth factors, but can grow in serum.
• This suggests the presence of an unidentified growth factor in serum that supports cell growth independently of IGF-IR signaling.

Purpose of the Study:

• To identify the unknown growth factor present in serum that promotes cell proliferation in R- cells.
• To screen conditioned media from various cell lines for growth-stimulating activity on R- cells.

Main Methods:

• Utilized R- cells as a model system to screen for growth-promoting activity.
• Assayed conditioned media from different cell lines for their ability to stimulate DNA synthesis and cell proliferation in R- cells.
• Characterized the activity using ultrafiltration, heat denaturation, and proteinase K sensitivity.

Main Results:

• BRL-3A cell line conditioned medium exhibited significant growth and DNA synthesis stimulating activity on R- cells.
• The activity was found to be concentration-dependent.
• The active component is heat-labile, proteinase K-sensitive, and larger than 10 kDa.

Conclusions:

• A novel polypeptide with growth-promoting activity has been identified in BRL-3A cell conditioned medium.
• This factor stimulates proliferation in cells lacking functional IGF-IRs, indicating a new growth pathway.
• Further characterization of this novel growth factor is ongoing.