Limits...
BRAF inhibitors suppress apoptosis through off-target inhibition of JNK signaling.

Vin H, Ojeda SS, Ching G, Leung ML, Chitsazzadeh V, Dwyer DW, Adelmann CH, Restrepo M, Richards KN, Stewart LR, Du L, Ferguson SB, Chakravarti D, Ehrenreiter K, Baccarini M, Ruggieri R, Curry JL, Kim KB, Ciurea AM, Duvic M, Prieto VG, Ullrich SE, Dalby KN, Flores ER, Tsai KY - Elife (2013)

Bottom Line: The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation.Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK.Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, University of Texas MD Anderson Cancer Center, Houston, United States.

ABSTRACT
Vemurafenib and dabrafenib selectively inhibit the v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) kinase, resulting in high response rates and increased survival in melanoma. Approximately 22% of individuals treated with vemurafenib develop cutaneous squamous cell carcinoma (cSCC) during therapy. The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation. Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK. JNK signaling is suppressed in multiple contexts, including in cSCC of vemurafenib-treated patients, as well as in mice. Expression of a mutant ZAK that cannot be inhibited reverses the suppression of JNK activation and apoptosis. Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies. DOI: http://dx.doi.org/10.7554/eLife.00969.001.

Show MeSH

Related in: MedlinePlus

Dabrafenib produces a colony formation advantage only in WT MEFs.At 0.05 μM, dabrafenib produce a significant growth advantage in E1A-HRASG12V- transformed WT MEFs. In E1A-HRASG12V-transformed Craf−/− MEFs, dabrafenib fails to confer a significant growth advantage, suggesting that in the absence of significant paradoxical ERK activation, dabrafenib does not have a relevant off-target effect that results in a growth advantage.DOI:http://dx.doi.org/10.7554/eLife.00969.025
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3814616&req=5

fig6s3: Dabrafenib produces a colony formation advantage only in WT MEFs.At 0.05 μM, dabrafenib produce a significant growth advantage in E1A-HRASG12V- transformed WT MEFs. In E1A-HRASG12V-transformed Craf−/− MEFs, dabrafenib fails to confer a significant growth advantage, suggesting that in the absence of significant paradoxical ERK activation, dabrafenib does not have a relevant off-target effect that results in a growth advantage.DOI:http://dx.doi.org/10.7554/eLife.00969.025

Mentions: Using transformed WT and Craf-deficient MEFs in soft agar assays, we also showed that dabrafenib enhanced colony formation in WT MEFs, but not in Craf-deficient MEFs (Figure 6—figure supplement 3). Our results suggest that while both dabrafenib and vemurafenib cause equivalent paradoxical ERK activation in BRAF-wild-type cells (Figure 6—figure supplement 1A–B), only vemurafenib confers a significant colony formation advantage in Craf-deficient cells that have no significant paradoxical MEK/ERK activation, implicating off-target effects as a key difference between the two drugs with respect to cSCC development (Menzies et al., 2013).


BRAF inhibitors suppress apoptosis through off-target inhibition of JNK signaling.

Vin H, Ojeda SS, Ching G, Leung ML, Chitsazzadeh V, Dwyer DW, Adelmann CH, Restrepo M, Richards KN, Stewart LR, Du L, Ferguson SB, Chakravarti D, Ehrenreiter K, Baccarini M, Ruggieri R, Curry JL, Kim KB, Ciurea AM, Duvic M, Prieto VG, Ullrich SE, Dalby KN, Flores ER, Tsai KY - Elife (2013)

Dabrafenib produces a colony formation advantage only in WT MEFs.At 0.05 μM, dabrafenib produce a significant growth advantage in E1A-HRASG12V- transformed WT MEFs. In E1A-HRASG12V-transformed Craf−/− MEFs, dabrafenib fails to confer a significant growth advantage, suggesting that in the absence of significant paradoxical ERK activation, dabrafenib does not have a relevant off-target effect that results in a growth advantage.DOI:http://dx.doi.org/10.7554/eLife.00969.025
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3814616&req=5

fig6s3: Dabrafenib produces a colony formation advantage only in WT MEFs.At 0.05 μM, dabrafenib produce a significant growth advantage in E1A-HRASG12V- transformed WT MEFs. In E1A-HRASG12V-transformed Craf−/− MEFs, dabrafenib fails to confer a significant growth advantage, suggesting that in the absence of significant paradoxical ERK activation, dabrafenib does not have a relevant off-target effect that results in a growth advantage.DOI:http://dx.doi.org/10.7554/eLife.00969.025
Mentions: Using transformed WT and Craf-deficient MEFs in soft agar assays, we also showed that dabrafenib enhanced colony formation in WT MEFs, but not in Craf-deficient MEFs (Figure 6—figure supplement 3). Our results suggest that while both dabrafenib and vemurafenib cause equivalent paradoxical ERK activation in BRAF-wild-type cells (Figure 6—figure supplement 1A–B), only vemurafenib confers a significant colony formation advantage in Craf-deficient cells that have no significant paradoxical MEK/ERK activation, implicating off-target effects as a key difference between the two drugs with respect to cSCC development (Menzies et al., 2013).

Bottom Line: The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation.Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK.Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, University of Texas MD Anderson Cancer Center, Houston, United States.

ABSTRACT
Vemurafenib and dabrafenib selectively inhibit the v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) kinase, resulting in high response rates and increased survival in melanoma. Approximately 22% of individuals treated with vemurafenib develop cutaneous squamous cell carcinoma (cSCC) during therapy. The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation. Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK. JNK signaling is suppressed in multiple contexts, including in cSCC of vemurafenib-treated patients, as well as in mice. Expression of a mutant ZAK that cannot be inhibited reverses the suppression of JNK activation and apoptosis. Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies. DOI: http://dx.doi.org/10.7554/eLife.00969.001.

Show MeSH
Related in: MedlinePlus