Low expression of the PPARγ-regulated gene thioredoxin-interacting protein accompanies human melanoma progression and promotes experimental lung metastases

The thioredoxin system plays key roles in regulating cancer cell malignancy. Here we identify the Thioredoxin-interacting protein (TXNIP) as a gene, which expression is regulated by PPARγ in melanoma cells. We show that high TXNIP expression levels associate with benign melanocytic lesions, with tumor regression in patients on MAP kinase targeted therapy, with decreased proliferation in patients’ melanoma biopsies, and with cell cycle arrest in human melanoma cell lines. In contrast, reduced TXNIP expression associates with advanced melanoma and with disease progression in patients. TXNIP depletion in human melanoma cells altered the expression of integrin beta-3 and the localization of the integrin alpha-v/beta-3 dimer at their surface. Moreover, TXNIP depletion affected human melanoma cell motility and improved their capacity to colonize mouse lungs in an in vivo assay. This study establishes TXNIP as a PPARγ-regulated gene in melanoma cells, thereby suggesting a link between these two proteins both involved in the regulation of cancer and of energy metabolism. It also reveals that the decrease in TXNIP expression, which is observed in advanced patient tumors, likely favors lung metastatic seeding of malignant cells.

Mixed Response to Immunotherapy in Patients with Metastatic Melanoma

Background

Immunotherapy has improved overall survival in metastatic melanoma. Response to therapy can be difficult to evaluate as the traditionally used RECIST 1.1 criteria do not capture heterogeneous responses. Here we describe the clinical characterization of melanoma patients with a clinically defined mixed response to immunotherapy.

Methods

This was a single institution, retrospective analysis of stage IV melanoma patients who received first-line anti-CTLA-4, anti-PD1, or combination anti-CTLA-4/anti-PD1. Therapy response was assessed via clinical definitions, which consisted of cross-sectional imaging combined with clinical exam. Course of disease, clinicopathological characteristics, and management in patients with a mixed clinical response were analyzed.

Results

In 292 patients (anti-CTLA4 = 63; anti-PD1 = 148, anti-CTLA4/anti-PD1 = 81), 103 were responders (35%), 64 mixed responders (22%), and 125 patients had progressive disease (43%). Of patients with a mixed response, 56% eventually had response to therapy (mixed response followed by response, MR–R), while 31% progressed on therapy (MR–NR). MR–NR patients had higher median LDH (p < 0.01), 3 or more organ sites with metastases (p < 0.01), and more frequently had M1d disease (p < 0.01). Mixed responders who underwent surgery (n = 20) had a significantly longer mean OS compared to patients who did not undergo surgery (6.9 years, 95% CI 6.2–7.6 vs. 6.0 years, 95% CI 4.6–7.3, p = 0.02).

Discussion

Mixed response to immunotherapy in metastatic melanoma was not uncommon in our cohort (22%). Clinical characteristics associated with progression of disease after initial mixed response included higher LDH, brain metastases, and ≥ 3 organ sites with metastases. Surgical treatment for highly selected patients with a mixed response was associated with improved outcomes.

Adjuvant Therapy Failure Patterns in the Modern Era of Melanoma Management

BACKGROUND

The management of patients with resected stage 3 melanoma has changed significantly due to adoption of the Multicenter Selective Lymphadenectomy Trial (MSLT)-2 guidelines and to the survival benefit of adjuvant anti-PD-1 immunotherapy and BRAF/MEK-inhibitor (BRAF/MEKi) therapy. Data are scarce regarding recurrence patterns, adjuvant therapy responses, and therapy-associated adverse events (AEs) in the modern era.

METHODS

This single-institution, retrospective study analyzed surgically resected stage 3 and oligometastatic stage 4 patients who received anti-PD-1, BRAF/MEKi, or surgery with active surveillance only. The primary end point of the study was recurrence-free survival (RFS). The secondary end points were the location and clinical characteristics of recurrence and therapy-associated AEs.

RESULTS

From a cohort of 137 patients, the study enrolled 102 patients treated with adjuvant anti-PD-1 (n = 46), adjuvant BRAF/MEKi (n = 3), or surgery alone (n = 26). During a mean follow-up period of 17 months, 20% of the ani-PD-1 patients, 13% of the BRAF/MEKi patients, and 42% of the surgery-only patients experienced recurrence. Log-rank testing showed a significantly longer RFS for the patients treated with anti-PD-1 [15.3 months; interquartile range (IQR), 8.2-23.2 months; p = 0.04] or BRAF/MEKi (17.9 months; IQR, 12.5-23 months; p = 0.01) than for those treated with surgery alone (11.9 months; IQR, 7.0-17.6 months). In the anti-PD-1 group, AEs occurred less frequently than in the BRAF/MEKi group (54% vs 80%; p = 0.03).

CONCLUSIONS

Adjuvant anti-PD-1 and BRAF/MEKi were associated with significantly improved RFS for the patients with resected stage 3 or 4 melanoma. The BRAF/MEKi group had significantly more AEs than the anti-PD-1 group. This is the first study to characterize real-world recurrence in the modern era of adjuvant therapy for melanoma.

Tumor-associated B-cells induce tumor heterogeneity and therapy resistance

In melanoma, therapies with inhibitors to oncogenic BRAFV600E are highly effective but responses are often short-lived due to the emergence of drug-resistant tumor subpopulations. We describe here a mechanism of acquired drug resistance through the tumor microenvironment, which is mediated by human tumor-associated B cells. Human melanoma cells constitutively produce the growth factor FGF-2, which activates tumor-infiltrating B cells to produce the growth factor IGF-1. B-cell-derived IGF-1 is critical for resistance of melanomas to BRAF and MEK inhibitors due to emergence of heterogeneous subpopulations and activation of FGFR-3. Consistently, resistance of melanomas to BRAF and/or MEK inhibitors is associated with increased CD20 and IGF-1 transcript levels in tumors and IGF-1 expression in tumor-associated B cells. Furthermore, first clinical data from a pilot trial in therapy-resistant metastatic melanoma patients show anti-tumor activity through B-cell depletion by anti-CD20 antibody. Our findings establish a mechanism of acquired therapy resistance through tumor-associated B cells with important clinical implications.Resistance to BRAFV600E inhibitors often occurs in melanoma patients. Here, the authors describe a potential mechanism of acquired drug resistance mediated by tumor-associated B cells-derived IGF-1.

BRAF inhibition increases tumor infiltration by T cells and enhances the antitumor activity of adoptive immunotherapy in mice

PURPOSE

Treatment of melanoma patients with selective BRAF inhibitors results in objective clinical responses in the majority of patients with BRAF-mutant tumors. However, resistance to these inhibitors develops within a few months. In this study, we test the hypothesis that BRAF inhibition in combination with adoptive T-cell transfer (ACT) will be more effective at inducing long-term clinical regressions of BRAF-mutant tumors.

EXPERIMENTAL DESIGN

BRAF-mutated human melanoma tumor cell lines transduced to express gp100 and H-2D(b) to allow recognition by gp100-specific pmel-1 T cells were used as xenograft models to assess melanocyte differentiation antigen-independent enhancement of immune responses by BRAF inhibitor PLX4720. Luciferase-expressing pmel-1 T cells were generated to monitor T-cell migration in vivo. The expression of VEGF was determined by ELISA, protein array, and immunohistochemistry. Importantly, VEGF expression after BRAF inhibition was tested in a set of patient samples.

RESULTS

We found that administration of PLX4720 significantly increased tumor infiltration of adoptively transferred T cells in vivo and enhanced the antitumor activity of ACT. This increased T-cell infiltration was primarily mediated by the ability of PLX4720 to inhibit melanoma tumor cell production of VEGF by reducing the binding of c-myc to the VEGF promoter. Furthermore, analysis of human melanoma patient tumor biopsies before and during BRAF inhibitor treatment showed downregulation of VEGF consistent with the preclinical murine model.

CONCLUSION

These findings provide a strong rationale to evaluate the potential clinical application of combining BRAF inhibition with T-cell-based immunotherapy for the treatment of patients with melanoma.

BRAF inhibition increases tumor infiltration by T cells and enhances the antitumor activity of adoptive immunotherapy in mice

PURPOSE

Treatment of melanoma patients with selective BRAF inhibitors results in objective clinical responses in the majority of patients with BRAF-mutant tumors. However, resistance to these inhibitors develops within a few months. In this study, we test the hypothesis that BRAF inhibition in combination with adoptive T-cell transfer (ACT) will be more effective at inducing long-term clinical regressions of BRAF-mutant tumors.

EXPERIMENTAL DESIGN

BRAF-mutated human melanoma tumor cell lines transduced to express gp100 and H-2D(b) to allow recognition by gp100-specific pmel-1 T cells were used as xenograft models to assess melanocyte differentiation antigen-independent enhancement of immune responses by BRAF inhibitor PLX4720. Luciferase-expressing pmel-1 T cells were generated to monitor T-cell migration in vivo. The expression of VEGF was determined by ELISA, protein array, and immunohistochemistry. Importantly, VEGF expression after BRAF inhibition was tested in a set of patient samples.

RESULTS

We found that administration of PLX4720 significantly increased tumor infiltration of adoptively transferred T cells in vivo and enhanced the antitumor activity of ACT. This increased T-cell infiltration was primarily mediated by the ability of PLX4720 to inhibit melanoma tumor cell production of VEGF by reducing the binding of c-myc to the VEGF promoter. Furthermore, analysis of human melanoma patient tumor biopsies before and during BRAF inhibitor treatment showed downregulation of VEGF consistent with the preclinical murine model.

CONCLUSION

These findings provide a strong rationale to evaluate the potential clinical application of combining BRAF inhibition with T-cell-based immunotherapy for the treatment of patients with melanoma.