Combination of chemotherapy with BRAF inhibitors results in effective eradication of malignant melanoma by preventing ATM-dependent DNA repair

NEMO is essential for directing the kinases IKKα and ATM to the sites of DNA damage

The DNA damage repair kinase ATM is phosphorylated by the NF-κB pathway kinase IKKα, resulting in enhanced DNA damage repair through the nonhomologous end-joining pathway. Thus, inhibition of IKKα enhances the efficacy of cancer therapy based on inducing DNA damage. Here, we found a role for the IKK regulatory subunit NEMO in DNA damage repair mediated by ATM and IKKα. Exposure to damaging agents induced the interaction of NEMO with a preformed ATM-IKKα complex, which was required to target active ATM and IKKα to chromatin for efficient DNA damage repair but not for activating ATM. Recognition of damaged DNA by the IKKα-NEMO-ATM complex was facilitated by the interaction between NEMO and histones and depended on the ADP ribosylation of histones by the enzyme PARP1. NEMO-deficient cells showed increased activity of the kinase ATR, and inhibition of ATR potentiated the effect of chemotherapy in cells lacking NEMO or IKKα. Bioinformatic analysis of colorectal cancer datasets demonstrated that the expression of genes encoding IKKα, NEMO, and ATM correlated with poor patient prognosis, suggesting that the mechanism linking these three elements may be clinically relevant.

BRAF-Mutated Melanoma Cell Lines Develop Distinct Molecular Signatures After Prolonged Exposure to AZ628 or Dabrafenib: Potential Benefits of the Antiretroviral Treatments Cabotegravir or Doravirine on BRAF-Inhibitor-Resistant Cells

Melanoma is an aggressive cancer characterized by rapid growth, early metastasis, and poor prognosis, with resistance to current therapies being a significant issue. BRAF mutations drive uncontrolled cell division by activating the MAPK pathway. In this study, A375 and FO-1, BRAF-mutated melanoma cell lines, were treated for 4-5 months with RAF inhibitor dabrafenib or AZ628, leading to drug resistance over time. The resistant cells showed altered molecular signatures, with differences in cell cycle regulation and the propensity of cell death. Dabrafenib-resistant cells maintained high proliferative activity, while AZ628-resistant cells, especially A375 cells, exhibited slow-cycling, and a senescent-like phenotype with high susceptibility to ferroptosis, a form of cell death driven by iron. Antiretroviral drugs doravirine and cabotegravir, known for their effects on human endogenous retroviruses, were tested for their impact on these resistant melanoma cells. Both drugs reduced cell viability and colony formation in resistant cell lines. Doravirine was particularly effective in reactivating apoptosis and reducing cell growth in highly proliferative resistant cells by increasing tumor-suppressor proteins p16Ink4a and p27Kip1. These findings suggest that antiretroviral drugs can influence apoptosis and cell proliferation in RAF-inhibitor-resistant melanoma cells, offering potential therapeutic strategies for overcoming drug resistance.

Chemotherapy in Cutaneous Melanoma: Is There Still a Role?

Purpose of Review

In the preceding decade, the management of metastatic cutaneous melanoma has been revolutionised with the development of highly effective therapies including immune checkpoint inhibitors (specifically CTLA-4 and PD-1 inhibitors) and targeted therapies (BRAF and MEK inhibitors). The role of chemotherapy in the contemporary management of melanoma is undefined.

Recent Findings

Extended analyses highlight substantially improved 5-year survival rates of approximately 50% in patients with metastatic melanoma treated with first-line therapies. However, most patients will progress on these first-line treatments. Sequencing of chemotherapy following failure of targeted and immunotherapies is associated with low objective response rates and short progression-free survival, and thus, meaningful benefits to patients are minimal.

Summary

Chemotherapy has limited utility in the contemporary management of cutaneous melanoma (with a few exceptions, discussed herein) and should not be the standard treatment sequence following failure of first-line therapies. Instead, enrolment onto clinical trials should be standard-of-care in these patients.

ROR2 increases the chemoresistance of melanoma by regulating p53 and Bcl2-family proteins via ERK hyperactivation

Background

ROR2 is a tyrosine-kinase receptor whose expression is dysregulated in many human diseases. In cancer, ROR2 stimulates proliferation, survival, migration, and metastasis, and is associated with more aggressive tumor stages. The purpose of this work is to study the role of ROR2 in the chemoresistance of melanoma.

Methods

Gain- and loss-of-function experiments were used to study the biological function of ROR2 in melanoma. Cell death induced by chemotherapeutic drugs and BH-3 mimetics was evaluated using crystal violet cytotoxicity assays and annexin V/propidium iodide staining. Western blots were used to evaluate the expression of proteins implicated in cell death. The differences observed between cells with manipulation of ROR2 levels and control cells were evaluated using both Student’s t-test and ANOVA.

Results

We describe that ROR2 contributes to tumor progression by enhancing the resistance of melanoma cells to both chemotherapeutic drugs and BH-3 mimetics. We demonstrate that ROR2 reduced cell death upon treatment with cisplatin, dacarbazine, lomustine, camptothecin, paclitaxel, ABT-737, TW-37, and venetoclax. This effect was mediated by the inhibition of apoptosis. In addition, we investigated the molecular mechanisms implicated in this role of ROR2. We identified the MDM2/p53 pathway as a novel target of ROR2 since ROR2 positively regulates MDM2 levels, thus leading to p53 downregulation. We also showed that ROR2 also upregulates Mcl-1 and Bcl2-xL while it negatively regulates Bax and Bid expression. The effect of ROR2 on the expression of these proteins is mediated by the hyperactivation of ERK.

Conclusions

These results demonstrate that ROR2 contributes to melanoma progression by inhibiting apoptosis and increasing chemoresistance. These results not only position ROR2 as a marker of chemoresistance but also support its use as a novel therapeutic target in cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00327-7.