Limits...
Activated mutant NRas(Q61K) drives aberrant melanocyte signaling, survival, and invasiveness via a Rac1-dependent mechanism.

Li A, Ma Y, Jin M, Mason S, Mort RL, Blyth K, Larue L, Sansom OJ, Machesky LM - J. Invest. Dermatol. (2012)

Bottom Line: The Ras oncogene also activates signaling via the related Rho GTPase Rac1, which can mediate growth, survival, and motility signaling.We tested the effects of activated NRas(Q61K) on the proliferation, motility, and invasiveness of melanoblasts and melanocytes in the developing mouse and ex vivo explant culture as well as in a melanoma transplant model.We also show that genetic deletion or pharmacological inhibition of Rac1 in NRas(Q61K) induced melanoma suppresses tumor growth, lymph node spread, and tumor cell invasiveness, suggesting a potential value for Rac1 as a therapeutic target for activated NRas-driven tumor growth and invasiveness.

View Article: PubMed Central - PubMed

Affiliation: The Beatson Institute for Cancer Research, Garscube Estate, Glasgow, UK.

ABSTRACT
Around a fifth of melanomas exhibit an activating mutation in the oncogene NRas that confers constitutive signaling to proliferation and promotes tumor initiation. NRas signals downstream of the major melanocyte tyrosine kinase receptor c-kit and activated NRas results in increased signaling via the extracellular signal-regulated kinase (ERK)/MAPK/ERK kinase/mitogen-activated protein kinase (MAPK) pathways to enhance proliferation. The Ras oncogene also activates signaling via the related Rho GTPase Rac1, which can mediate growth, survival, and motility signaling. We tested the effects of activated NRas(Q61K) on the proliferation, motility, and invasiveness of melanoblasts and melanocytes in the developing mouse and ex vivo explant culture as well as in a melanoma transplant model. We find an important role for Rac1 downstream of NRas(Q61K) in mediating dermal melanocyte survival in vivo in mouse, but surprisingly NRas(Q61K) does not appear to affect melanoblast motility or proliferation during mouse embryogenesis. We also show that genetic deletion or pharmacological inhibition of Rac1 in NRas(Q61K) induced melanoma suppresses tumor growth, lymph node spread, and tumor cell invasiveness, suggesting a potential value for Rac1 as a therapeutic target for activated NRas-driven tumor growth and invasiveness.

Show MeSH

Related in: MedlinePlus

Rac1 is required for NRasQ61K-induced survival of murine dermal melanocytes. (a) Number of melanocytes in epi/dermis at P0.5, P3, and P5 per field ( × 10 objective) from (⩾3 pups, 3 litters). Dorsal skin from P14 control (Ctr) (b), NRas Ctr (c), and Rac1 f/f NRas (d) mice with anti-dopachrome tautomerase (melanocytes). High-magnification images of hair follicle and dermis shows typical cluster of excess dermal melanocytes in NRas mouse (arrow). (e) Number of patches (⩾5 cells) of melanocytes in dermis per field at P14 (from ⩾3 pups, 3 litters). (f) Number of patches (⩾5 cells) of melanocytes in dermis or former hair bulb per field at P21 (from ⩾3 pups, 3 litters). **P<0.01 by t-test. Bars=100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3472562&req=5

fig3: Rac1 is required for NRasQ61K-induced survival of murine dermal melanocytes. (a) Number of melanocytes in epi/dermis at P0.5, P3, and P5 per field ( × 10 objective) from (⩾3 pups, 3 litters). Dorsal skin from P14 control (Ctr) (b), NRas Ctr (c), and Rac1 f/f NRas (d) mice with anti-dopachrome tautomerase (melanocytes). High-magnification images of hair follicle and dermis shows typical cluster of excess dermal melanocytes in NRas mouse (arrow). (e) Number of patches (⩾5 cells) of melanocytes in dermis per field at P14 (from ⩾3 pups, 3 litters). (f) Number of patches (⩾5 cells) of melanocytes in dermis or former hair bulb per field at P21 (from ⩾3 pups, 3 litters). **P<0.01 by t-test. Bars=100 μm.

Mentions: Before birth, murine melanoblasts reside in the dermis and epidermis (Luciani et al., 2011), but shortly after birth they reside only in hair follicles (Kelsh et al., 2009). We investigated the origin of Tyr∷NRasQ61K dermal melanocyte clusters (Figure 2h, arrow) and the effect of Rac1 loss during the first hair cycle, which is synchronous (Fuchs, 2007). Dorsal skin from control, Tyr∷NRasQ61K control, Rac1 f/f Tyr∷Cre and Tyr∷NRasQ61K Rac1 f/f Tyr∷Cre mice at P0.5, 3, 5, 14, and 21 was sectioned and stained with dopachrome tautomerase antibody to localize melanocytes. In control, Rac1 f/f Tyr∷Cre and Tyr∷NRasQ61K Rac1 f/f Tyr∷Cre mice, melanocytes in epidermis and dermis gradually disappeared from P0.5 to P5 (Figure 3a, Supplementary Figure S4A and C online and data not shown), leaving only hair follicle melanocytes (Hirobe, 1984; Kelsh et al., 2009). However, in Tyr∷NRasQ61K control mice, melanocytes in epidermis survived from P0.5 and number of melanocytes in epidermis increased over the hair cycle (Figure 3a, Supplementary Figure S4B online), indicating that expression of NRasQ61K promotes Rac1-dependent postnatal melanocyte survival and/or growth in epidermis.


Activated mutant NRas(Q61K) drives aberrant melanocyte signaling, survival, and invasiveness via a Rac1-dependent mechanism.

Li A, Ma Y, Jin M, Mason S, Mort RL, Blyth K, Larue L, Sansom OJ, Machesky LM - J. Invest. Dermatol. (2012)

Rac1 is required for NRasQ61K-induced survival of murine dermal melanocytes. (a) Number of melanocytes in epi/dermis at P0.5, P3, and P5 per field ( × 10 objective) from (⩾3 pups, 3 litters). Dorsal skin from P14 control (Ctr) (b), NRas Ctr (c), and Rac1 f/f NRas (d) mice with anti-dopachrome tautomerase (melanocytes). High-magnification images of hair follicle and dermis shows typical cluster of excess dermal melanocytes in NRas mouse (arrow). (e) Number of patches (⩾5 cells) of melanocytes in dermis per field at P14 (from ⩾3 pups, 3 litters). (f) Number of patches (⩾5 cells) of melanocytes in dermis or former hair bulb per field at P21 (from ⩾3 pups, 3 litters). **P<0.01 by t-test. Bars=100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472562&req=5

fig3: Rac1 is required for NRasQ61K-induced survival of murine dermal melanocytes. (a) Number of melanocytes in epi/dermis at P0.5, P3, and P5 per field ( × 10 objective) from (⩾3 pups, 3 litters). Dorsal skin from P14 control (Ctr) (b), NRas Ctr (c), and Rac1 f/f NRas (d) mice with anti-dopachrome tautomerase (melanocytes). High-magnification images of hair follicle and dermis shows typical cluster of excess dermal melanocytes in NRas mouse (arrow). (e) Number of patches (⩾5 cells) of melanocytes in dermis per field at P14 (from ⩾3 pups, 3 litters). (f) Number of patches (⩾5 cells) of melanocytes in dermis or former hair bulb per field at P21 (from ⩾3 pups, 3 litters). **P<0.01 by t-test. Bars=100 μm.
Mentions: Before birth, murine melanoblasts reside in the dermis and epidermis (Luciani et al., 2011), but shortly after birth they reside only in hair follicles (Kelsh et al., 2009). We investigated the origin of Tyr∷NRasQ61K dermal melanocyte clusters (Figure 2h, arrow) and the effect of Rac1 loss during the first hair cycle, which is synchronous (Fuchs, 2007). Dorsal skin from control, Tyr∷NRasQ61K control, Rac1 f/f Tyr∷Cre and Tyr∷NRasQ61K Rac1 f/f Tyr∷Cre mice at P0.5, 3, 5, 14, and 21 was sectioned and stained with dopachrome tautomerase antibody to localize melanocytes. In control, Rac1 f/f Tyr∷Cre and Tyr∷NRasQ61K Rac1 f/f Tyr∷Cre mice, melanocytes in epidermis and dermis gradually disappeared from P0.5 to P5 (Figure 3a, Supplementary Figure S4A and C online and data not shown), leaving only hair follicle melanocytes (Hirobe, 1984; Kelsh et al., 2009). However, in Tyr∷NRasQ61K control mice, melanocytes in epidermis survived from P0.5 and number of melanocytes in epidermis increased over the hair cycle (Figure 3a, Supplementary Figure S4B online), indicating that expression of NRasQ61K promotes Rac1-dependent postnatal melanocyte survival and/or growth in epidermis.

Bottom Line: The Ras oncogene also activates signaling via the related Rho GTPase Rac1, which can mediate growth, survival, and motility signaling.We tested the effects of activated NRas(Q61K) on the proliferation, motility, and invasiveness of melanoblasts and melanocytes in the developing mouse and ex vivo explant culture as well as in a melanoma transplant model.We also show that genetic deletion or pharmacological inhibition of Rac1 in NRas(Q61K) induced melanoma suppresses tumor growth, lymph node spread, and tumor cell invasiveness, suggesting a potential value for Rac1 as a therapeutic target for activated NRas-driven tumor growth and invasiveness.

View Article: PubMed Central - PubMed

Affiliation: The Beatson Institute for Cancer Research, Garscube Estate, Glasgow, UK.

ABSTRACT
Around a fifth of melanomas exhibit an activating mutation in the oncogene NRas that confers constitutive signaling to proliferation and promotes tumor initiation. NRas signals downstream of the major melanocyte tyrosine kinase receptor c-kit and activated NRas results in increased signaling via the extracellular signal-regulated kinase (ERK)/MAPK/ERK kinase/mitogen-activated protein kinase (MAPK) pathways to enhance proliferation. The Ras oncogene also activates signaling via the related Rho GTPase Rac1, which can mediate growth, survival, and motility signaling. We tested the effects of activated NRas(Q61K) on the proliferation, motility, and invasiveness of melanoblasts and melanocytes in the developing mouse and ex vivo explant culture as well as in a melanoma transplant model. We find an important role for Rac1 downstream of NRas(Q61K) in mediating dermal melanocyte survival in vivo in mouse, but surprisingly NRas(Q61K) does not appear to affect melanoblast motility or proliferation during mouse embryogenesis. We also show that genetic deletion or pharmacological inhibition of Rac1 in NRas(Q61K) induced melanoma suppresses tumor growth, lymph node spread, and tumor cell invasiveness, suggesting a potential value for Rac1 as a therapeutic target for activated NRas-driven tumor growth and invasiveness.

Show MeSH
Related in: MedlinePlus