The INK4a/ARF locus encodes the cyclin dependent kinase inhibitor, p16INK4a and the p53 activator, p14ARF. These two proteins have an independent ®rst exon (exon 1a and exon 1b, respectively) but share exons 2 and 3 and are translated in dierent reading frames. Germline mutations in this locus are associated with melanoma susceptibility in 20 ± 40% of multiple case melanoma families. Although most of these mutations speci®cally inactivate p16 INK4a, more than 40% of the INK4a/ARF alterations located in exon 2, aect both p16INK4a and p14ARF. We now report a 16 base pair exon 1b germline insertion speci®cally altering p14ARF, but not p16 INK4a, in an individual with multiple primary melanomas. This mutant p14ARF, 60ins16, was restricted to the cytoplasm, did not stabilize p53 and was unable to arrest the growth of a p53 expressing melanoma cell line. This is the ®rst example of an exon 1b mutation that inactivates p14ARF, and thus implicates a role for this tumour suppressor in melanoma predisposition. Oncogene (2001) 20, 5543 ± 5547.

Clinical responses to bendamustine in chronic lymphocytic leukemia (CLL) are highly heterogeneous and no specific markers to predict sensitivity to this drug have been reported. In order to identify biomarkers of response, we analyzed the in vitro activity of bendamustine and the gene expression profile in primary CLL cells. We observed that mRNA expression of CD69 (CD69) and ITGAM (CD11b) constitute the most powerful predictor of response to bendamustine. When we interrogated the predictive value of the corresponding cell surface proteins, the expression of the activation marker CD69 was the most reliable predictor of sensitivity to bendamustine. Importantly, a multivariate analysis revealed that the predictive value of CD69 expression was independent from other clinico-biological CLL features. We also showed that when CLL cells were co-cultured with distinct subtypes of stromal cells, an upregulation of CD69 was accompanied by a reduced sensitivity to bendamustine. In agreement with this, tumor cells derived from lymphoid tumor niches harbored higher CD69 expression and were less sensitive to bendamustine than their peripheral blood counterparts. Furthermore, pretreatment of CD69 high CLL cases with the B-cell receptor (BCR) pathway inhibitors ibrutinib and idelalisib decreased CD69 levels and enhanced bendamustine cytotoxic effect. Collectively, our findings indicate that CD69 could be a predictor of bendamustine response in CLL patients and the combination of clinically-tested BCR signaling inhibitors with bendamustine may represent a promising strategy for bendamustine low responsive CLL cases.

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