Mechanistic validation of a clinical lead stapled peptide that reactivates p53 by dual HDM2 and HDMX targeting.

Hydrocarbon-stapled peptides that display key residues of the p53 transactivation domain have emerged as bona fide clinical candidates for reactivating the tumor suppression function of p53 in cancer by dual targeting of the negative regulators HDM2 and HDMX. A recent study questioned the mechanistic specificity of such stapled peptides based on interrogating their capacity to disrupt p53/HDM2 and p53/HDMX complexes in living cells using a new recombinase enhanced bimolecular luciferase complementation platform (ReBiL). Here, we directly evaluate the cellular uptake, intracellular targeting selectivity and p53-dependent cytotoxicity of the clinical prototype ATSP-7041. We find that under standard serum-containing tissue culture conditions, ATSP-7041 achieves intracellular access without membrane disruption, dose-dependently dissociates both p53/HDM2 and p53/HDMX complexes but not an unrelated protein complex in long-term ReBiL experiments, and is selectively cytotoxic to cancer cells bearing wild-type p53 by inducing a surge in p53 protein level. These studies underscore the importance of a thorough stepwise approach, including consideration of the time-dependence of cellular uptake and intracellular distribution, in evaluating and advancing stapled peptides for clinical translation.

[Polyradiculoneuropathy in an adult with primitive hyperoxaluria]. / Polyradiculoneuropathie au cours d'une hyperoxalurie primitive de l'adulte.

From the age of 31 a patient began to suffer from recurrent calcium oxalate urolithiasis. Liver biopsy showed a decrease in catalytic activity of the hepatic peroxisomal enzyme alanine: glyoxilate aminotransferase (AGT), which was mistargeted from peroxisomes to mitochondria. The genetic analysis revealed a mutation of the AGT gene. At age 47 he developed end-stage renal failure and underwent hemodialysis. After 12 months of hemodialysis he presented a rapidly declining clinical condition, a decrease of the residual renal function, a livedo reticularis with painful of extremities, and shortly thereafter a general weakness, which predominated on lower limbs. Apart from renal failure, routine biological examination and CSF were normal. Nerve conduction studies and electromyography supported the diagnosis of polyradiculoneuropathy. Pathological studies revealed mixed demyelinating-axonal lesions and deposits of calcium oxalate crystals within the media and the intima of epineural arterioles. A combined liver-kidney transplant was rapidly performed. The patient's condition improved in a few months and motor signs completely disappeared.