Molecularly matched targeted therapy: a promising approach for refractory metastatic melanoma.

BACKGROUND: Only a fraction of patients with metastatic melanoma derive durable benefit from approved treatments. The clinical impact of personalized medicine strategies for melanoma, apart from BRAF, NRAS, or CKIT targeting, has rarely been reported. MATERIALS AND METHODS: By means of the Group of Cutaneous Oncology of the French Society of Dermatology, we retrospectively included all patients with advanced melanoma aged 18 years and older for whom molecular testing identified one or more actionable molecular alterations and who accordingly received molecularly matched therapy. We excluded patients with only BRAF, NRAS, or CKIT alterations and patients who received molecularly matched therapy for less than 15 days. RESULTS: We included 26 patients with a median follow-up of 8 months (1-54), a median age of 63 years (24-89), and a sex ratio of 2.7. These patients had been heavily pretreated, and 64% had elevated LDH levels. The disease control rate was 38%, with 4 cases of partial response (overall response rate: 15%) and 6 of stable disease for at least 6 months. The median duration of treatment was 3.1 months (0.9-13.5). Among patients with disease control, the median duration of control was 6.6 months (2.6-13.5) and 3 cases were ongoing at the end of the study. Patients with controlled disease had GNA11, MAP2K1, FYCO1-RAF1, HRAS, ATM, CCND1, MDM2/CDK4, and CDKN2A/NRAS alterations. CONCLUSIONS: High-throughput sequencing followed by matched targeted therapy is a promising approach for patients with advanced melanoma refractory to approved treatments.

Impact of systemic therapies in metastatic melanoma of unknown primary: A study from MELBASE, a French multicentric prospective cohort.

BACKGROUND: Clinical outcomes of advanced melanoma of unknown primary (MUP) in the era of novel therapies have been scarcely studied. OBJECTIVE: To investigate the efficacy and safety of systemic treatments in patients with advanced MUP compared to patients with stage-matched melanoma of known cutaneous primary (cMKP). METHODS: Based on the nationwide MelBase prospective database, this study included advanced melanoma patients treated from March 2013 to June 2021 with first-line immunotherapies, targeted therapies, or chemotherapy. Co-primary outcomes were progression-free survival and overall survival. Secondary outcome was treatment-related toxicities. Multivariate and propensity score analyses were performed. RESULTS: Of 1882 patients, 265 (14.1%) had advanced MUP. Patients with advanced MUP displayed more often unfavorable initial prognostic factors than those with cMKP. Progression-free and overall survival did not differ significantly between the groups (P = .73 and P = .93, respectively), as well as treatment-related toxicity rate and severity, regardless of treatment type. LIMITATIONS: No record of standard diagnostic criteria of MUP used in the participating centers. CONCLUSIONS: Although patients with MUP had less favorable baseline prognostic factors, they benefited from the novel therapies as much as those with cMKP. They should be managed according to similar strategies.

Anti-PD-1 for the treatment of advanced cutaneous squamous cell carcinoma in elderly patients: a French multicenter retrospective survey.

BACKGROUND: Anti-PD1 agents are currently recommended as first-line treatment in advanced cutaneous squamous cell carcinoma (acSCC) by updated European guidelines. Although acSCC frequently affects elderly patients with multiple comorbidities, this subset of patients is often excluded of registration clinical trials. PURPOSE: To assess anti-PD-1 efficacy and safety in elderly acSCC patients in real-life conditions and describe this specific population with oncogeriatric evaluation tools. METHODS: A multicenter retrospective study including acSCC patients at least 70 years old treated with PD-1 inhibitors was conducted in French referral centers. The primary endpoint was the overall response rate (ORR). Secondary endpoints included safety data, time to response (TTR), duration of response (DOR), overall survival (OS), and progression-free survival (PFS). RESULTS: 63 patients were included. ORR was 57.1% (95% CI 44.0-69.5), median TTR and DOR were 3 and 5.5 months respectively. Median OS was not reached (95% CI 12.5 months-not reached) at data cut-off after a median follow-up of 8 months while median PFS was 8 months. (95% CI 5 months-not reached). Grade 3-5 adverse effects occurred in 47.6% of patients. 41.3% of patients experienced degradation of ECOG performance status during anti-PD-1 treatment. Nutritional state worsened in 27% of patients and 57.1% lost weight during treatment. CONCLUSION: In this particular subset of acSCC patients PD-1 inhibitors obtain results similar to those obtained in younger populations included in pivotal clinical trials, with acceptable safety. A specific oncogeriatric evaluation at treatment initiation and during follow-up appears important in this setting most notably to help manage toxicity.

Cost-Effectiveness Analysis of Sequential Treatment Strategies for Advanced Melanoma in Real Life in France.

Nine drugs have been marketed for 10 years for the treatment of advanced melanoma (AM). With half of patients reaching a second line, the optimal sequence of treatments remains unclear. To inform policy-makers about their efficiency, we performed a cost-effectiveness analysis of sequential strategies in clinical practice in France, for BRAF-mutated and wild-type patients. A multistate model was developed to describe treatment sequences, associated costs, and health outcomes over 10 years. Sequences, clinical outcomes, utility scores, and economic data were extracted from the prospective Melbase cohort, collecting individual data in 1518 patients since 2013, from their AM diagnosis until their death. To adjust the differences in patients' characteristics among sequences, weighting by inverse probability was used. In the BRAF-mutated population, the MONO-targeted therapies (TT)-anti-PD1 sequence was the less expensive, whereas the anti-PD1-BI-TT sequence had an incremental cost-effectiveness ratio (ICER) of 180,441 EUR/QALY. Regarding the BRAF wild-type population, the three sequences constituted the cost-effective frontier, with ICERs ranging from 116 to 806,000 EUR/QALY. For BRAF-mutated patients, the sequence anti-PD1-BI-TT appeared to be the most efficient one in BRAF-mutated AM patients until 2018. Regarding the BRAF wild-type population until 2018, the sequence starting with IPI+NIVO appeared inefficient compared to anti-PD1, considering the extra cost for the QALY gained.

Non-V600E/K BRAF Mutations in Metastatic Melanoma: Molecular Description, Frequency, and Effectiveness of Targeted Therapy in a Large National Cohort.

PURPOSE: Mitogen-activating protein kinase inhibitors (MAPKis) are largely used in V600E/K BRAF-mutated metastatic melanomas, but data regarding effectiveness of targeted therapy in patients with rare BRAF mutations and molecular description of these infrequent mutations are scarce. PATIENTS AND METHODS: A multicenter study was conducted on patients with metastatic melanoma harboring a well-identified mutation of BRAF and enrolled from March 2013 to June 2021 in the French nationwide prospective cohort MelBase. The molecular BRAF mutation pattern, response to MAPKis when applicable, and survival data were analyzed. RESULTS: Of 856 selected patients, 51 (6%) harbored a non-V600E/K BRAF mutation involving codons V600 (24 of 51, 47%; V600G 27.4%, V600R 15.6%), K601 (6 of 51, 11.7%), and L597 (4 of 51, 7.8%). An objective response to MAPKis either BRAF inhibitor (BRAFi) alone or combined with MEK inhibitor was achieved in 56% (353 of 631) of V600E/K, 58% (11 of 19) of non-E/K V600, and 22% (2 of 9) of non-V600 BRAF-mutated patients, with a median progression-free survival of 7.7, 7.8, and 2.8 months, respectively. Overall, objective response rate was higher with BRAFi + MEK inhibitor combination than with BRAFi in monotherapy for each subset. CONCLUSION: Rare BRAF mutations are not anecdotal in the metastatic melanoma population. Although data interpretation must remain careful owing to the limited size of some subsets of patients, non-E/K V600 BRAF mutations seem to confer a high sensitivity to targeted therapy, whereas MAPKis seem less effective in patients with non-V600 BRAF mutations. However, this strategy may be used as an alternative option in the case of immunotherapy failure in the latter population.

Risk of irAEs in patients with autoimmune diseases treated by immune checkpoint inhibitors for stage III or IV melanoma: results from a matched case-control study.

OBJECTIVE: To quantify the risk of immune-related adverse events (irAEs) in patients with pre-existing autoimmune disease (pAID) treated by immune checkpoint inhibitors (ICIs) for stage III or IV melanoma. METHODS: Case-control study performed on a French multicentric prospective cohort of patients with melanoma, matched for irAE risk factors and oncological staging. Risk of irAE was assessed by logistic regression. RESULTS: 110 patients with pAID were included and matched with 330 controls, from March 2013 to October 2020. Over a median follow-up period of 7.2 months for cases and 6.9 months for controls, the ORs of developing all-grade and grade ≥3 irAEs among cases compared with controls were 1.91 (95% CI (1.56 to 2.27)) and 1.44 (95% CI (1.08 to 1.82)), respectively. Patients with pAID had an increased risk of multiple irAEs (OR 1.46, 95% CI (1.15 to 2.67)) and a shorter time to irAE onset. In contrast, there were no difference in irAE-related mortality nor in the rate of treatment discontinuation, and a landmark analysis revealed a better survival at 24 months among cases (p=0.02). Thirty per cent of cases experienced a pAID flare during follow-up, and baseline immunosuppression did not prevent irAE occurrence. Last, we report associations between the pAID clinical subsets and organ-specific irAEs. CONCLUSION: In our study, patients with pAID were at greater risk of all-grade, severe and multiple irAEs, yet had a better 24-month survival than controls. Thus, patients with pAID should be eligible for ICI therapy but benefit from a close monitoring for irAE occurrence, especially during the first months of therapy.

Extracellular 20S proteasome secreted via microvesicles can degrade poorly folded proteins and inhibit Galectin-3 agglutination activity.

Proteasomes are major non-lysosomal proteolytic complexes localized in the cytoplasm and in the nucleus of eukaryotic cells. Strikingly, high levels of extracellular proteasome have also been evidenced in the plasma (p-proteasome) of patients with specific diseases. Here, we examined the process by which proteasomes are secreted, as well as their structural and functional features once in the extracellular space. We demonstrate that assembled 20S core particles are secreted by cells within microvesicles budding from the plasma membrane. Part of the extracellular proteasome pool is also free of membranes in the supernatant of cultured cells, and likely originates from microvesicles leakage. We further demonstrate that this free proteasome released by cells (cc-proteasome for cell culture proteasome) possesses latent proteolytic activity and can degrade various extracellular proteins. Both standard (no immune-subunits) and intermediate (containing some immune-subunits) forms of 20S are observed. Moreover, we show that galectin-3, which displays a highly disordered N-terminal region, is efficiently cleaved by purified cc-proteasome, without SDS activation, likely after its binding to PSMA3 (α7) subunit through its intrinsically disordered region. As a consequence, galectin-3 is unable to induce red blood cells agglutination when preincubated with cc-proteasome. These results highlight potential novel physio- and pathologic functions for the extracellular proteasome.

Tolerance and Effectiveness of Targeted Therapies in Aged Patients with Metastatic Melanoma.

PURPOSE: Melanoma's incidence is increasing, and elderly people could be significantly impacted since the majority occurs in people over 65 years of age. Combined BRAF and MEK targeted therapies (TT) are current standard regimen for BRAF mutated metastatic melanoma (MM). Except for subgroups of pivotal trials, little data are available for TT in this population. MATERIALS AND METHODS: Outcomes were explored in real life patients from MelBase, a French multicentric biobank dedicated to the prospective follow-up of unresectable stage III or IV melanoma. Patients treated by BRAF TT and/or MEK TT combined or not, were included from 2013 to 2017 in 2 groups: group 1 ≤ 65-year-old (yo), group 2 > 65 yo, analyzed for tolerance and efficacy. RESULTS: 353 patients were included: 231 in group 1, 122 in group 2. Median follow-up was 12 months (M). Median time of treatment was 6.9 M. A total of 80% had at least one Adverse Effect (AE). Most frequent AE (all grades) were mainly skin and subcutaneous, general, and gastrointestinal disorders. A total of 31% of AE were grade 3-4: 28% in group 1 and 39% in group 2 (p = 0.05). No differences were observed in all AE grades proportion, dose modifications, interruptions, and discontinuations. For each group, median overall survival was 20.3 M (CI 95%: 15.5-27.9) and 16.3 M (CI: 14.5-26.9), respectively (p = 0.8). Median progression free survival was 7.8 M (6.4-9.9) and 7.7 M (CI: 5.8-11.3) (p = 0.4). Objective response rate was 59% and 50% (p = 0.6). CONCLUSION: This study on a large multicentric cohort is the first to assess that TT is well tolerated in elderly BRAF-mutated patients such as in patients younger than 65. Efficacy was similar between groups with outcomes reaching those from pivotal studies. There is thus no argument against using TT in elderly people, although an onco-geriatric opinion is welcome for the most vulnerable.

Cemiplimab for Locally Advanced and Metastatic Cutaneous Squamous-Cell Carcinomas: Real-Life Experience from the French CAREPI Study Group.

Although cemiplimab has been approved for locally advanced (la) and metastatic (m) cutaneous squamous-cell carcinomas (CSCCs), its real-life value has not yet been demonstrated. An early-access program enrolled patients with la/mCSCCs to receive cemiplimab. Endpoints were best overall response rate (BOR), progression-free survival (PFS), overall survival (OS), duration of response (DOR) and safety. The 245 patients (mean age 77 years, 73% male, 49% prior systemic treatment, 24% immunocompromised, 27% Eastern Cooperative Oncology Group performance status (PS) ≥ 2) had laCSCCs (35%) or mCSCCs (65%). For the 240 recipients of ≥1 infusion(s), the BOR was 50.4% (complete, 21%; partial, 29%). With median follow-up at 12.6 months, median PFS was 7.9 months, and median OS and DOR were not reached. One-year OS was 73% versus 36%, respectively, for patients with PS < 2 versus ≥ 2. Multivariate analysis retained PS ≥ 2 as being associated during the first 6 months with PFS and OS. Head-and-neck location was associated with longer PFS. Immune status had no impact. Severe treatment-related adverse events occurred in 9% of the patients, including one death from toxic epidermal necrolysis. Cemiplimab real-life safety and efficacy support its use for la/mCSCCs. Patients with PS ≥ 2 benefited less from cemiplimab, but it might represent an option for immunocompromised patients.

Melanotransferrin is efficiently sorted on the surface of exosomes secreted by melanoma cells.

Cutaneous melanoma is the most lethal type of skin cancer. Early detection is crucial to improve the outcome of melanoma patients. The identification of noninvasive prognostic biomarkers for the follow-up of melanoma patients is still in demand for clinical use. We show here that exosomal melanotransferrin fulfills the biomarker characteristics required to meet this demand. Melanotransferrin is typically overexpressed in melanoma cells compared to other cell types - including cancer cells - and is efficiently sorted and secreted with nanovesicles, or so-called exosomes, due to its membrane-anchoring by a glycosylphosphatidylinositol. Melanotransferrin is exposed on the surface of exosomes and is accessible for antibody recognition. An ELISA was set up to quantify melanotransferrin after immobilization of nanovesicles through the exosomal constituent tetraspanins CD63. Melanotransferrin was detected using a low number of exosomes purified from melanoma cell line cultures, and melanotransferrin detection was abolished by phosphatidylinositol-specific phospholipase C treatment. This exosomal melanotransferrin ELISA was able to discriminate an equal number of assayed exosomes purified from two different melanoma cell lines (A-375 vs. SK-MEL-28). Moreover, plasma samples from patients with melanoma and noncancer disease were assayed using this ELISA and elevated levels of exosomal melanotransferrin were seen in the plasma of patients with melanoma. We propose that exosomal melanotransferrin should be assessed as a potential melanoma biomarker.

Quality-of-life assessment in French patients with metastatic melanoma in real life.

BACKGROUND: Significant progress was recently observed in the treatment of metastatic melanoma (MM). With >50% of patients now reaching a second line of treatment and a significant improvement in the survival rate, an assessment of quality of life (QoL) during the whole course of the disease becomes necessary. The objective of this study was to describe the QoL of patients with MM in France, from their diagnosis of advanced disease to their death, in real life. METHODS: QoL data were collected through MelBase, a prospective, French, multicentric cohort dedicated to the follow-up of adults with MM. QoL was assessed using the EuroQoL-5D questionnaire and the Functional Assessment of Cancer Treatment (FACT)-Melanoma questionnaire at the time of study inclusion, every 3 months, and at the time of each treatment change until death. To assess longitudinal changes from baseline to death, mixed-effect models for repeated-measures analyses were used to control for baseline covariates. RESULTS: QoL was assessed in 1435 patients who were included in the study between 2013 and 2018. The median follow-up was 9.4 months, and 47% of patients died during follow-up. During first-line treatment, the model-based, mean utility score was 0.830 (95% CI, 0.818-0.843), the mean FACT-General score was 77.22 (95% CI, 76.23-78.22), and the mean FACT-Melanoma score was 129.46 (95% CI, 128.02-130.90). At the time of a change in treatment line, there was a decrease of -0.027 (95% CI, -0.03, -0.02) in the utility score, -1.82 (95% CI, -1.88, -1.76) in the FACT-General score, and -2.98 (95% CI, -3.05, -2.91) in the FACT-Melanoma score compared with first-line treatment. CONCLUSIONS: In the MelBase cohort, the QoL among patients with MM seems to be fairly stable over the whole disease course, although a small but significant decrease at time therapy is changed is observed.

S100-EPISPOT: A New Tool to Detect Viable Circulating Melanoma Cells.

Metastatic melanoma is one of the most aggressive and drug-resistant cancers with very poor overall survival. Circulating melanoma cells (CMCs) were first described in 1991. However, there is no general consensus on the clinical utility of CMC detection, largely due to conflicting results linked to the use of heterogeneous patient populations and different detection methods. Here, we developed a new EPithelial ImmunoSPOT (EPISPOT) assay to detect viable CMCs based on their secretion of the S100 protein (S100-EPISPOT). Then, we compared the results obtained with the S100-EPISPOT assay and the CellSearch® CMC kit using blood samples from a homogeneous population of patients with metastatic melanoma. We found that S100-EPISPOT sensitivity was significantly higher than that of CellSearch®. Specifically, the percentage of patients with ≥2 CMCs was significantly higher using S100-EPISPOT than CellSearch® (48% and 21%, respectively; p = 0.0114). Concerning CMC prognostic value, only the CellSearch® results showed a significant association with overall survival (p = 0.006). However, due to the higher sensitivity of the new S100-EPISPOT assay, it would be interesting to determine whether this functional test could be used in patients with non-metastatic melanoma for the early detection of tumor relapse and for monitoring the treatment response.

Proteasome 19S RP and translation preinitiation complexes are secreted within exosomes upon serum starvation.

The aim of our study was to investigate the impact of macroautophagy on exosome secretion. Exosomes are small membrane vesicles released in the extracellular space upon fusion of multivesicular endosomes with the plasma membrane. They were initially discovered as a way to remodel the reticulocyte plasma membrane before entering the blood circulation (Current Opinion in Hematology 2010, 17:177-183) and are now essentially studied as mediators of intercellular communication. Using iTRAQ proteomics, we compared the protein composition of purified exosomes secreted by cells impaired or not for macroautophagy by Atg5 depletion, during serum starvation conditions or complete medium culture. We show that the absence of serum modifies exosomal content, especially inducing secretion of two cytoplasmic protein complexes, namely proteasomal 19S regulatory particle (RP) and components of noncanonical translation preinitiation complex (PIC). This process is enhanced when autophagy is impaired by Atg5 depletion. Moreover, we show that the proteasome 20S core particle (CP) is released in the extracellular space. However, in striking contrast to what seen for its 19S RP regulator, release is independent of the exosomal vesicles, Atg5 expression and cell culture conditions. Exosome secretion can thus be considered as a cell process that participates in and reflects cell homeostasis, and care must be taken when studying potential extracellular function of exosomes due to the possible copurification of proteasome 20S CP.

Association of Time From Primary Diagnosis to First Distant Relapse of Metastatic Melanoma With Progression of Disease and Survival.

Importance: The prognosis of advanced melanoma has been greatly improved by new therapeutic agents and clinicians rely on dynamic signals to drive their therapeutic choices. Although the kinetics of metastatic disease seem to be correlated with survival, progression of the localized disease is not predictable. Objective: To assess whether progression of metastatic disease is associated with the time to the first distant recurrence of melanoma. Design, Setting, and Participants: This study was conducted from March 1, 2013, to September 1, 2017, among 638 adults with unresectable stage III or IV melanoma within the French multicentric prospective cohort MelBase. Patients treated with first-line immunotherapies, targeted therapies, or chemotherapy were included. Patients with unknown primary or de novo metastatic melanoma were not included. Data were analyzed from March 1, 2013, to December 1, 2017. Main Outcomes and Measures: The date of primary excision and time to first distant recurrence, progression-free survival, and overall survival were collected. Cox proportional hazards regression models were planned to assess the association between time to first distant recurrence and progression-free survival or overall survival, which was evaluated in terms of hazard ratio (HR). Time to recurrence was analyzed both as a continuous and categorical variable (<12 months, 12-24 months, and >24 months). Results: A total of 638 patients (272 women and 366 men; median age, 64 years [interquartile range, 52-73 years]) were included in the study. The median time from primary excision to first distant recurrence was 25 months (interquartile range, 12-55 months). There was no evidence of association of the time to recurrence with progression-free survival, both when analyzed as a continuous variable (HR, 0.99; 95% CI, 0.99-1.01) or after categorization (12-24 months: HR, 0.75; 95% CI, 0.56-1.02; >24 months: HR, 0.62; 95% CI; 0.47-1.01). There was no evidence of association of the time to recurrence with overall survival, both when analyzed as a continuous variable (HR, 0.99; 95% CI, 0.98-1.02) or after categorization (12-24 months: HR, 0.76; 95% CI, 0.54-1.07; >24 months: HR, 0.61; 95% CI, 0.54-1.03). Those results remained nonsignificant after stratification by treatment. Conclusions and Relevance: In the MelBase cohort, time to recurrence of metastatic melanoma appears not to be associated with progression-free survival or overall survival.

Impact of radiotherapy administered simultaneously with systemic treatment in patients with melanoma brain metastases within MelBase, a French multicentric prospective cohort.

BACKGROUND: Melanoma brain metastases (MBMs) are historically associated with poor prognosis. Radiation therapy is conventionally associated with a high local control rate. Development of targeted therapy and immunotherapy has improved overall survival (OS) and intracranial response rate, but about 50% of patients failed to respond to these novel therapies. The objective of this study was to assess the impact of combined radiotherapy (cRT) on overall survival in a large multicenter real-life prospective cohort of patients with MBM treated with immunotherapy or targeted therapy. PATIENTS AND METHODS: Clinical data from 262 patients with MBM were collected via MelBase, a French multicentric biobank prospectively enrolling unresectable stage III or IV melanoma. Two groups were defined: patients receiving cRT (cRT group) or not receiving cRT (no-cRT group). Primary end-point was OS. Propensity score weighting was used to correct for indication bias. RESULTS: Among the 262 patients, 93 (35%) received cRT (cRT group). The patients were treated with immunotherapy in 69% and 60% and with targeted therapy in 31% and 40% of the cRT and no-cRT groups, respectively. With a median follow-up of 6.9 months, median OS was 16.8 months and 6.9 months in the cRT and no-cRT groups, respectively. After propensity score weighting, cRT was associated with longer OS (hazard ratio = 0.6, 95% confidence interval: 0.4-0.8; p=0.007). Median OS after ponderation was 15.3 months and 6.2 months in the cRT and no-cRT groups, respectively. CONCLUSION: This study shows that cRT may be associated with a significant decrease of 40% in the risk of death in patients with MBM treated with systemic therapy.

The proteasome maturation protein POMP increases proteasome assembly and activity in psoriatic lesional skin.

BACKGROUND: The ubiquitin proteasome pathway is involved in the pathogenesis of psoriasis and proteasome subunits are increased in lesional psoriatic skin. Recent works have highlighted that proteasome levels can be regulated through modulation of proteasome assembly notably by the proteasome maturation protein POMP. OBJECTIVES: To investigate whether proteasome assembly and POMP expression are modified in psoriatic skin. METHODS: Proteasome assembly as well as expression of proteasome regulators were assessed in non-lesional and lesional psoriatic skin using native gel electrophoresis and western blots respectively. The protein and mRNA expression levels of POMP were compared by western blots, immunohistochemistry and quantitative polymerase chain reaction. The role of POMP in keratinocyte proliferation and differentiation was assessed by silencing POMP gene expression by RNA interference in human immortalized keratinocyte HaCaT cells. RESULTS: Both 20S and 26S proteasomes (and their respective proteolytic activities) as well as the main proteasome regulators are increased in lesional psoriatic skin. POMP binds to 20S precursor complexes and is overexpressed in lesional epidermal psoriatic skin, supporting that POMP-mediated proteasome assembly is increased in psoriatic skin. POMP silencing inhibited HaCaT cell proliferation and induced apoptosis through the inhibition of the proteasome assembly. Moreover POMP partial depletion decreased the expression of the differentiation markers keratin 10 and involucrin during the [Ca2+]-induced HaCaT cells differentiation. CONCLUSION: Altogether these results establish a potential role for POMP and proteasome assembly in psoriasis pathogenesis.