p15Ink4b is a critical tumour suppressor in the absence of p16Ink4a

Article metrics


The CDKN2b–CDKN2a locus on chromosome 9p21 in human (chromosome 4 in mouse) is frequently lost in cancer. The locus encodes three cell cycle inhibitory proteins: p15INK4b encoded by CDKN2b, p16INK4a encoded by CDKN2a and p14ARF (p19Arf in mice) encoded by an alternative reading frame of CDKN2a (ref. 1). Whereas the tumour suppressor functions for p16INK4a and p14ARF have been firmly established, the role of p15INK4b remains ambiguous. However, many 9p21 deletions also remove CDKN2b, so we hypothesized a synergistic effect of the combined deficiency for p15INK4b, p14ARF and p16INK4a. Here we report that mice deficient for all three open reading frames (Cdkn2ab-/-) are more tumour-prone and develop a wider spectrum of tumours than Cdkn2a mutant mice, with a preponderance of skin tumours and soft tissue sarcomas (for example, mesothelioma) frequently composed of mixed cell types and often showing biphasic differentiation. Cdkn2ab-/- mouse embryonic fibroblasts (MEFs) are substantially more sensitive to oncogenic transformation than Cdkn2a mutant MEFs. Under conditions of stress, p15Ink4b protein levels are significantly elevated in MEFs deficient for p16Ink4a. Our data indicate that p15Ink4b can fulfil a critical backup function for p16Ink4a and provide an explanation for the frequent loss of the complete CDKN2b–CDKN2a locus in human tumours.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Generation of Ink4ab -/- and Cdkn2ab -/- mice.
Figure 2: Cdkn2ab -/- mice develop skin tumours and sarcomatous lesions.
Figure 3: MEF analysis.
Figure 4: Analysis of oncogenically transformed MEFs.


  1. 1

    Gil, J. & Peters, G. Regulation of the INK4bARFINK4a tumour suppressor locus: all for one or one for all. Nature Rev. Mol. Cell Biol. 7, 667–677 (2006)

  2. 2

    Ortega, S., Malumbres, M. & Barbacid, M. Cyclin D-dependent kinases, INK4 inhibitors and cancer. Biochim. Biophys. Acta 1602, 73–87 (2002)

  3. 3

    Pomerantz, J. et al. The Ink4a tumor suppressor gene product, p19Arf, interacts with MDM2 and neutralizes MDM2’s inhibition of p53. Cell 92, 713–723 (1998)

  4. 4

    Drexler, H. G. Review of alterations of the cyclin-dependent kinase inhibitor INK4 family genes p15, p16, p18 and p19 in human leukemia-lymphoma cells. Leukemia 12, 845–859 (1998)

  5. 5

    Krug, U., Ganser, A. & Koeffler, H. P. Tumor suppressor genes in normal and malignant hematopoiesis. Oncogene 21, 3475–3495 (2002)

  6. 6

    Murao, K., Kubo, Y., Ohtani, N., Hara, E. & Arase, S. Epigenetic abnormalities in cutaneous squamous cell carcinomas: frequent inactivation of the RB1/p16 and p53 pathways. Br. J. Dermatol. 155, 999–1005 (2006)

  7. 7

    Orlow, I. et al. Alterations of INK4A and INK4B genes in adult soft tissue sarcomas: effect on survival. J. Natl. Cancer Inst. 91, 73–79 (1999)

  8. 8

    Ruas, M. & Peters, G. The p16INK4a/CDKN2A tumor suppressor and its relatives. Biochim. Biophys. Acta 1378, F115–F177 (1998)

  9. 9

    Serrano, M. et al. Role of the INK4a locus in tumor suppression and cell mortality. Cell 85, 27–37 (1996)

  10. 10

    Kamijo, T. et al. Tumor suppression at the mouse INK4a locus mediated by the alternative reading frame product p19ARF. Cell 91, 649–659 (1997)

  11. 11

    Kamijo, T., Bodner, S., van de Kamp, E., Randle, D. H. & Sherr, C. J. Tumor spectrum in ARF-deficient mice. Cancer Res. 59, 2217–2222 (1999)

  12. 12

    Sharpless, N. E. et al. Loss of p16Ink4a with retention of p19Arf predisposes mice to tumorigenesis. Nature 413, 86–91 (2001)

  13. 13

    Krimpenfort, P., Quon, K. C., Mooi, W. J., Loonstra, A. & Berns, A. Loss of p16Ink4a confers susceptibility to metastatic melanoma in mice. Nature 413, 83–86 (2001)

  14. 14

    Kim, W. Y. & Sharpless, N. E. The regulation of INK4/ARF in cancer and aging. Cell 127, 265–275 (2006)

  15. 15

    Latres, E. et al. Limited overlapping roles of P15INK4b and P18INK4c cell cycle inhibitors in proliferation and tumorigenesis. EMBO J. 19, 3496–3506 (2000)

  16. 16

    Zou, X. et al. Cdk4 disruption renders primary mouse cells resistant to oncogenic transformation, leading to Arf/p53-independent senescence. Genes Dev. 16, 2923–2934 (2002)

  17. 17

    Pantoja, C., Palmero, I. & Serrano, M. Identification of the gene immediately downstream of the murine INK4a/ARF locus. Exp. Gerontol. 36, 1289–1302 (2001)

  18. 18

    Sharpless, N. E., Ramsey, M. R., Balasubramanian, P., Castrillon, D. H. & DePinho, R. A. The differential impact of p16INK4a or p19ARF deficiency on cell growth and tumorigenesis. Oncogene 23, 379–385 (2004)

  19. 19

    Parry, D., Mahony, D., Wills, K. & Lees, E. Cyclin D–CDK subunit arrangement is dependent on the availability of competing INK4 and p21 class inhibitors. Mol. Cell. Biol. 19, 1775–1783 (1999)

  20. 20

    Fahraeus, R. & Lane, D. P. The p16INK4a tumour suppressor protein inhibits αvβ3 integrin-mediated cell spreading on vitronectin by blocking PKC-dependent localization of αvβ3 to focal contacts. EMBO J. 18, 2106–2118 (1999)

  21. 21

    Harrison, P. T. An ethanol-acetic acid-formol saline fixative for routine use with special application to the fixation of non-perfused rat lung. Lab. Anim. 18, 325–331 (1984)

  22. 22

    Deng, C., Zhang, P., Harper, J. W., Elledge, S. J. & Leder, P. Mice lacking p21CIP1/WAF1 undergo normal development, but are defective in G1 checkpoint control. Cell 82, 675–684 (1995)

  23. 23

    Bagui, T. K., Mohapatra, S., Haura, E. & Pledger, W. J. P27Kip1 and p21Cip1 are not required for the formation of active D cyclin–cdk4 complexes. Mol. Cell. Biol. 23, 7285–7290 (2003)

  24. 24

    Lyons, S. K., Meuwissen, R., Krimpenfort, P. & Berns, A. The generation of a conditional reporter that enables bioluminescence imaging of Cre/loxP-dependent tumorigenesis in mice. Cancer Res. 63, 7042–7046 (2003)

Download references


We thank R. B. Ali for assistance in generating the mice, the staff of the NKI animal facility for providing animal care, the staff of the histology department for the processing of tissues, J. de Ridder for help with statistical analysis, L. Vredeveld and C. Michaloglou for help with soft agar assays, and R. van Amerongen and the group of D. Peeper for discussions. This work was supported by the Dutch Cancer Society.

Author information

Correspondence to Anton Berns.

Ethics declarations

Competing interests

Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Discussion and Supplementary Figures S1-S5 with Legends (PDF 1657 kb)

Rights and permissions

Reprints and Permissions

About this article

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.