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Expression of the c-raf protooncogene in human hematopoietic cells and cell lines
Abstract:
The murine sarcoma virus 3611 contains the transforming v-raf gene that has partial nucleotide homology with the src family of tyrosine kinase-encoding oncogenes. Although this virus induces fibrosarcomas in mice, a recombinant murine retrovirus carrying both the raf and myc oncogenes induces immunoblastic lymphomas and immortalizes mouse macrophages in vitro. The present study has thus monitored the expression of c-raf in human hematopoietic cells. The results demonstrate the presence of a 3.6-kb c-raf transcript in HL-60 promyelocytic leukemic cells. The induction of HL-60 cell differentiation along the monocytic or granulocytic lineages had no detectable effect on the level of c-raf transcripts. Furthermore, in contrast to c-myc and c-fms expression, inhibition of protein synthesis with cycloheximide had no detectable effect on c-raf expression. Similar levels of c-rafRNA were also found in other human cell lines derived from myeloid, B cell, and T cell tumors, as well as in normal granulocytes, monocytes, and macrophages. These findings suggest that the c-raf protooncogene is widely expressed in multiple hematopoietic lineages.
Insights
The c-raf protooncogene is widely expressed across various human hematopoietic cells, including both normal and cancerous myeloid, B cell, and T cell lineages. Its expression remains stable during cell differentiation and is independent of protein synthesis.
Area of Science:
- Molecular Biology
- Oncology
- Hematology
Background:
- The v-raf gene, found in murine sarcoma virus 3611, shares homology with src family tyrosine kinases.
- While v-raf induces fibrosarcomas, co-expression with c-myc leads to lymphomas and macrophage immortalization in mice.
Purpose of the Study:
- To investigate the expression patterns of the c-raf protooncogene in human hematopoietic cells.
- To determine if c-raf expression is altered during HL-60 cell differentiation or protein synthesis inhibition.
Main Methods:
- Northern blot analysis to detect c-raf transcripts in HL-60 cells and other human cell lines.
- Monitoring c-raf expression during induced differentiation of HL-60 cells.
- Assessing the impact of cycloheximide (protein synthesis inhibitor) on c-raf expression.
Main Results:
- A 3.6-kb c-raf transcript was detected in HL-60 promyelocytic leukemic cells.
- HL-60 cell differentiation into monocytic or granulocytic lineages did not affect c-raf transcript levels.
- Cycloheximide treatment did not alter c-raf expression, unlike c-myc and c-fms.
- Consistent c-raf RNA levels were observed in various human myeloid, B cell, and T cell tumor lines, as well as normal hematopoietic cells.
Conclusions:
- The c-raf protooncogene exhibits broad expression across diverse human hematopoietic lineages.
- c-raf expression appears to be regulated independently of differentiation-induced changes and protein synthesis in these cells.