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Updated: Sep 29, 2026
Methods for Evaluating the Role of c-Fos and Dusp1 in Oncogene Dependence
Published on: January 7, 2019
Chemical genetic blockade of transformation reveals dependence on aberrant oncogenic signaling
Qi-Wen Fan1, Chao Zhang, Kevan M Shokat
1Department of Neurology, University of California, San Francisco, CA 94143, USA.
Background:
Our understanding of protein kinase inhibition in the treatment of cancer is clearly limited by the lack of inhibitors that selectively block a single kinase implicated in neoplastic transformation. One approach to developing specific inhibitors is to engineer in protein kinases silent mutations that allow selective inhibition while retaining kinase activity. Because it is implicated in a large number of malignancies, EGFR provides an attractive target for such selective kinase inhibition.
Results:
We generated an inhibitor-sensitized allele of the transforming receptor tyrosine kinase v-erbB. Transformation of immortalized rodent fibroblasts by sensitized versions of v-erbB (v-erbB-as1) was blocked by 1-napthyl PP1 (NaPP1), a cell-permeable ATP-competitive inhibitor. NaPP1 also reversed morphological transformation by v-erbB-as1. Signaling through MAP kinase and PI(3) kinase was initially blocked by inhibitor treatment and then recovered to levels comparable to those in nontransformed cells. Surprisingly, NaPP1-treated v-erbB-as1 cells failed to re-enter the cell cycle, showed decreased levels of D- and A-type cyclins, and showed increased levels of p27. To extend this result, we showed that NaPP1 treatment of v-Src-as1 cells also led to cell cycle arrest. Arrested cells could be rescued with a conditional allele of Raf or by transduction of a constitutive allele of cyclin D1.
Conclusions:
These data suggest that mammalian cells can become dependent on aberrant oncogenic signaling; this dependency renders them incapable of returning to a normal, proliferative phenotype.
Insights
Targeted protein kinase inhibition for cancer treatment is challenging. Engineering specific mutations allows selective inhibition, revealing cancer cells can become dependent on aberrant signaling and lose proliferative capacity.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Selective protein kinase inhibitors are crucial for cancer therapy but are limited.
- Engineering kinases with silent mutations allows for targeted inhibition while preserving kinase function.
- Epidermal Growth Factor Receptor (EGFR) is a key target due to its role in numerous cancers.
Purpose of the Study:
- To develop and test an inhibitor-sensitized allele of the v-erbB receptor tyrosine kinase.
- To investigate the effects of selective inhibition on cancer cell transformation and proliferation.
- To explore the potential for targeting oncogenic signaling pathways in cancer treatment.
Main Methods:
- Generated an inhibitor-sensitized v-erbB allele (v-erbB-as1).
- Utilized 1-naphthyl PP1 (NaPP1), an ATP-competitive inhibitor, to block v-erbB-as1 activity.
- Assessed cell cycle progression, cyclin levels, and signaling pathway activation (MAP kinase, PI(3) kinase).
- Extended studies to v-Src-as1 cells and rescue experiments using conditional Raf or cyclin D1 alleles.
Main Results:
- NaPP1 treatment blocked and reversed v-erbB-as1-induced fibroblast transformation.
- Signaling pathways (MAP kinase, PI(3) kinase) were initially inhibited but recovered.
- v-erbB-as1 cells treated with NaPP1 arrested in the cell cycle, showing decreased cyclins and increased p27.
- v-Src-as1 cells also exhibited cell cycle arrest upon NaPP1 treatment.
- Cell cycle arrest could be rescued by modulating Raf or cyclin D1 expression.
Conclusions:
- Mammalian cells can develop a dependency on aberrant oncogenic signaling.
- This dependency prevents the return to a normal proliferative state even after inhibiting the oncogenic signal.
- Targeting oncogenic signaling pathways may lead to irreversible cell cycle arrest in cancer cells.
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