Christina Mateus

Anticancer immunotherapy by CTLA-4 blockade relies on the gut microbiota.

Gut microbes affect immunotherapy The unleashing of antitumor T cell responses has ushered in a new era of cancer treatment. Although these therapies can cause dramatic tumor regressions in some patients, many patients inexplicably see no benefit. Mice have been used in two studies to investigate what might be happening. Specific members of the gut microbiota influence the efficacy of this type of immunotherapy (see the Perspective by Snyder et al.). Vétizou et al. found that optimal responses to anticytotoxic T lymphocyte antigen blockade required specific Bacteroides spp. Similarly, Sivan et al. discovered that Bifidobacterium spp. enhanced the efficacy of antiprogrammed cell death ligand 1 therapy. Science, this issue, p. 1079 and p. 1084; see also p. 1031 Gut microbes modulate the effectiveness of cancer immunotherapies in mice. Antibodies targeting CTLA-4 have been successfully used as cancer immunotherapy. We find that the antitumor effects of CTLA-4 blockade depend on distinct Bacteroides species. In mice and patients, T cell responses specific for B. thetaiotaomicron or B. fragilis were associated with the efficacy of CTLA-4 blockade. Tumors in antibiotic-treated or germ-free mice did not respond to CTLA blockade. This defect was overcome by gavage with B. fragilis, by immunization with B. fragilis polysaccharides, or by adoptive transfer of B. fragilis–specific T cells. Fecal microbial transplantation from humans to mice confirmed that treatment of melanoma patients with antibodies against CTLA-4 favored the outgrowth of B. fragilis with anticancer properties. This study reveals a key role for Bacteroidales in the immunostimulatory effects of CTLA-4 blockade.

Reversible and adaptive resistance to BRAF(V600E) inhibition in melanoma

Treatment of BRAF(V600E) mutant melanoma by small molecule drugs that target the BRAF or MEK kinases can be effective, but resistance develops invariably. In contrast, colon cancers that harbour the same BRAF(V600E) mutation are intrinsically resistant to BRAF inhibitors, due to feedback activation of the epidermal growth factor receptor (EGFR). Here we show that 6 out of 16 melanoma tumours analysed acquired EGFR expression after the development of resistance to BRAF or MEK inhibitors. Using a chromatin-regulator-focused short hairpin RNA (shRNA) library, we find that suppression of sex determining region Y-box 10 (SOX10) in melanoma causes activation of TGF-β signalling, thus leading to upregulation of EGFR and platelet-derived growth factor receptor-β (PDGFRB), which confer resistance to BRAF and MEK inhibitors. Expression of EGFR in melanoma or treatment with TGF-β results in a slow-growth phenotype with cells displaying hallmarks of oncogene-induced senescence. However, EGFR expression or exposure to TGF-β becomes beneficial for proliferation in the presence of BRAF or MEK inhibitors. In a heterogeneous population of melanoma cells having varying levels of SOX10 suppression, cells with low SOX10 and consequently high EGFR expression are rapidly enriched in the presence of drug, but this is reversed when the drug treatment is discontinued. We find evidence for SOX10 loss and/or activation of TGF-β signalling in 4 of the 6 EGFR-positive drug-resistant melanoma patient samples. Our findings provide a rationale for why some BRAF or MEK inhibitor-resistant melanoma patients may regain sensitivity to these drugs after a ‘drug holiday’ and identify patients with EGFR-positive melanoma as a group that may benefit from re-treatment after a drug holiday.

eIF4F is a nexus of resistance to anti-BRAF and anti-MEK cancer therapies

In BRAF(V600)-mutant tumours, most mechanisms of resistance to drugs that target the BRAF and/or MEK kinases rely on reactivation of the RAS–RAF–MEK–ERK mitogen-activated protein kinase (MAPK) signal transduction pathway, on activation of the alternative, PI(3)K–AKT–mTOR, pathway (which is ERK independent) or on modulation of the caspase-dependent apoptotic cascade. All three pathways converge to regulate the formation of the eIF4F eukaryotic translation initiation complex, which binds to the 7-methylguanylate cap (m7G) at the 5′ end of messenger RNA, thereby modulating the translation of specific mRNAs. Here we show that the persistent formation of the eIF4F complex, comprising the eIF4E cap-binding protein, the eIF4G scaffolding protein and the eIF4A RNA helicase, is associated with resistance to anti-BRAF, anti-MEK and anti-BRAF plus anti-MEK drug combinations in BRAF(V600)-mutant melanoma, colon and thyroid cancer cell lines. Resistance to treatment and maintenance of eIF4F complex formation is associated with one of three mechanisms: reactivation of MAPK signalling, persistent ERK-independent phosphorylation of the inhibitory eIF4E-binding protein 4EBP1 or increased pro-apoptotic BCL-2-modifying factor (BMF)-dependent degradation of eIF4G. The development of an in situ method to detect the eIF4E–eIF4G interactions shows that eIF4F complex formation is decreased in tumours that respond to anti-BRAF therapy and increased in resistant metastases compared to tumours before treatment. Strikingly, inhibiting the eIF4F complex, either by blocking the eIF4E–eIF4G interaction or by targeting eIF4A, synergizes with inhibiting BRAF(V600) to kill the cancer cells. eIF4F not only appears to be an indicator of both innate and acquired resistance but also is a promising therapeutic target. Combinations of drugs targeting BRAF (and/or MEK) and eIF4F may overcome most of the resistance mechanisms arising in BRAF(V600)-mutant cancers.

Dermatologic symptoms associated with the multikinase inhibitor sorafenib

BACKGROUND The multikinase inhibitor sorafenib (Nexavar) is associated with a relatively high incidence of dermatologic symptoms. OBJECTIVE We sought to evaluate and provide guidance on the diagnosis and clinical management of dermatologic symptoms associated with sorafenib in patients with advanced solid tumors. METHODS English-language studies representative of a patient population with a variety of tumor types, who received single-agent sorafenib, were selected. Particular emphasis was placed on the phase III Treatment Approaches in Renal Cancer Global Evaluation Trial (TARGETs). RESULTS Frequently observed dermatologic side effects (any grade in TARGETs) of sorafenib include rash/desquamation (40%), hand-foot skin reaction (30%), alopecia (27%), and pruritus (19%). Generally, dermatologic symptoms resolve with appropriate management, including topical treatments, dose interruptions, dose reductions, or a combination of these. LIMITATIONS The results presented here are based on a limited number of studies. CONCLUSION Although sorafenib is associated with dermatologic symptoms, these are usually resolved with appropriate intervention, patient-led practical treatment, and preventative measures.

Nail toxicities induced by systemic anticancer treatments

Patients treated with systemic anticancer drugs often show changes to their nails, which are usually well tolerated and disappear on cessation of treatment. However, some nail toxicities can cause pain and functional impairment and thus substantially affect a patients quality of life, especially if they are given taxanes or EGFR inhibitors. These nail toxicities can affect both the nail plate and bed, and might present as melanonychia, leukonychia, onycholysis, onychomadesis, Beaus lines, or onychorrhexis, as frequently noted with conventional chemotherapies. Additionally, the periungual area (perionychium) of the nail might be affected by paronychia or pyogenic granuloma, especially in patients treated with drugs targeting EGFR or MEK. We review the nail changes induced by conventional chemotherapies and those associated with the use of targeted anticancer drugs and discuss preventive or curative options.

Cutaneous malignant melanoma in children and adolescents treated in pediatric oncology units

Recent progress in the understanding of tumor biology and new targeted therapies has led to improved survival in adults with malignant melanoma (MM). MM is rare in children, especially before puberty. We report here our experience with pediatric patients with MM, describe the clinical presentation, treatment and evolution, and compare prepubescent and postpubescent disease.

MAP-kinase pathway up or down? Just look at the skin of your patients!

Uribe et al. [1] report the case of a patient treated for metastatic melanoma with a combination of antiBRAF+ anti-MEK agents (dabrafenib+ trametinib). When the treatment was interrupted because of systemic intolerance (fever), the patient presented with a papulopustular rash similar to the one observed in patients treated with anti-MEK monotherapy. The rash disappeared when she resumed treatment. The authors propose that this sequence of events was related to the unbalance between BRAF and MEK inhibitions following treatment interruption as the half-life of trametinib is longer than that of dabrafenib. The hypothesis is that, during the few days of interruption, the patient was more under the influence of the anti-MEK than the antiBRAF agent.

L’immunothérapie dans le mélanomeImmunotherapies and melanoma

Metastatic melanoma treatment has been radically modified over the last four years with the emergence of new and effective therapeutic strategies targeted anti-BRAF therapies as well as immunotherapy. Following this latter immunotherapy strategy, anti-CTLA4 antibody ipilimumab demonstrated a benefit in terms of overall survival in patients with metastatic melanoma and is now challenged by other checkpoint inhibitors, antibodies directed against PD-1 and PD-L1 that have extremely promising benefit/risk ratio. Adverse events as well as evaluation criteria are different from the ones associated with classical chemotherapy or targeted therapies. The challenge for the next years will be to optimize these new strategies, by possibly using these new drugs sequentially or in combination for a higher clinical benefit for our patients.

L’immunothérapie dans le mélanome

Metastatic melanoma treatment has been radically modified over the last four years with the emergence of new and effective therapeutic strategies targeted anti-BRAF therapies as well as immunotherapy. Following this latter immunotherapy strategy, anti-CTLA4 antibody ipilimumab demonstrated a benefit in terms of overall survival in patients with metastatic melanoma and is now challenged by other checkpoint inhibitors, antibodies directed against PD-1 and PD-L1 that have extremely promising benefit/risk ratio. Adverse events as well as evaluation criteria are different from the ones associated with classical chemotherapy or targeted therapies. The challenge for the next years will be to optimize these new strategies, by possibly using these new drugs sequentially or in combination for a higher clinical benefit for our patients.