MYC promotes tyrosine kinase inhibitor resistance in ROS1 fusion-positive lung cancer

Recurrent mutations in tumor suppressor FBXW7 bypass Wnt/β-catenin addiction in cancer

Pathologic Wnt/β-catenin signaling drives various cancers, leading to multiple approaches to drug this pathway. Appropriate patient selection can maximize success of these interventions. Wnt ligand addiction is a druggable vulnerability in RNF43-mutant/RSPO-fusion cancers. However, pharmacologically targeting the biogenesis of Wnt ligands, e.g., with PORCN inhibitors, has shown mixed therapeutic responses, possibly due to tumor heterogeneity. Here, we show that the tumor suppressor FBXW7 is frequently mutated in RNF43-mutant/RSPO-fusion tumors, and FBXW7 mutations cause intrinsic resistance to anti-Wnt therapies. Mechanistically, FBXW7 inactivation stabilizes multiple oncoproteins including Cyclin E and MYC and antagonizes the cytostatic effect of Wnt inhibitors. Moreover, although FBXW7 mutations do not mitigate β-catenin degradation upon Wnt inhibition, FBXW7-mutant RNF43-mutant/RSPO-fusion cancers instead lose dependence on β-catenin signaling, accompanied by dedifferentiation and loss of lineage specificity. These FBXW7-mutant Wnt/β-catenin-independent tumors are susceptible to multi-cyclin-dependent kinase inhibition. An in-depth understanding of primary resistance to anti-Wnt/β-catenin therapies allows for more appropriate patient selection and use of alternative mechanism-based therapies.

From Development to Place in Therapy of Lorlatinib for the Treatment of ALK and ROS1 Rearranged Non-Small Cell Lung Cancer (NSCLC)

Following the results of the CROWN phase III trial, the third-generation macrocyclic ALK inhibitor lorlatinib has been introduced as a salvage option after the failure of a first-line TKI in ALK-rearranged NSCLC, while its precise role in the therapeutic algorithm of ROS1 positive disease is still to be completely defined. The ability to overcome acquired resistance to prior generation TKIs (alectinib, brigatinib, ceritinib, and crizotinib) and the high intracranial activity in brain metastatic disease thanks to increased blood-brain barrier penetration are the reasons for the growing popularity and interest in this molecule. Nevertheless, the major vulnerability of this drug resides in a peculiar profile of related collateral events, with neurological impairment being the most conflicting and debated clinical issue. The cognitive safety concern, the susceptibility to heterogeneous resistance pathways, and the absence of a valid alternative in the second line are strongly jeopardizing a potential paradigm shift in this oncogene-addicted disease. So, when prescribing lorlatinib, clinicians must face two diametrically opposed characteristics: a great therapeutic potential without the intrinsic limitations of its precursor TKIs, a cytotoxic activity threatened by suboptimal tolerability, and the unavoidable onset of resistance mechanisms we cannot properly manage yet. In this paper, we give a critical point of view on the stepwise introduction of this promising drug into clinical practice, starting from its innovative molecular and biochemical properties to intriguing future developments, without forgetting its weaknesses.

Uterine inflammatory myofibroblastic tumor harboring novel NUDCD3-ROS1 and NRP2-ALK fusions: clinicopathologic features of 4 cases and literature review

Inflammatory myofibroblastic tumor (IMT) is a mesenchymal neoplasm of intermediate biologic potential, which occurs mostly in the lung and abdomen cavity of children and young adults. Uterine IMTs are rare. Herein, we presented clinicopathologic features of 4 uterine IMTs. All four patients were initially diagnosed as leiomyosarcoma by other hospitals and corrected to uterine IMT after pathological consultation. Patient age ranged from 44 to 64 years old. Two cases demonstrated multiple masses. Microscopically, three tumors were composed of fascicular spindled cells with eosinophilic cytoplasm, and the other one was densely composed of spindled and epithelioid cells with bizarre and multinucleated cells. Tumor cells showed variable nuclear atypia, ranging from mild to severe. Prominent inflammatory cell infiltration was found in one case, and necrosis in two tumors. Immunochemistry staining revealed expression of smooth muscle markers in all four tumors, including a-SMA and desmin. Three tumors were positive for ALK protein expression. FISH analysis demonstrated ROS1 rearrangement in one tumor and ALK rearrangement in the other 3 tumors. NGS analysis showed novel NUDCD3-ROS1 and NRP2-ALK fusions in two tumors and TNS1-ALK fusion in the other two tumors. Gene aberrations involving p53 signaling pathway were identified in all four cases. All patients received surgery as primary treatment, and one had neoadjuvant chemotherapy. Three patients recurred within 12 months, and the other one recurred after 7 years. Patients with recurrence were treated with a combination of chemotherapy, targeted therapy, or surgery. In conclusion, the diagnosis of uterine IMTs can be challenging. Ancillary studies including ALK IHC, FISH, and NGS are helpful to establish diagnosis and to discover novel gene rearrangement potentially for targeted therapy.

Protein tyrosine kinase inhibitor resistance in malignant tumors: molecular mechanisms and future perspective

Protein tyrosine kinases (PTKs) are a class of proteins with tyrosine kinase activity that phosphorylate tyrosine residues of critical molecules in signaling pathways. Their basal function is essential for maintaining normal cell growth and differentiation. However, aberrant activation of PTKs caused by various factors can deviate cell function from the expected trajectory to an abnormal growth state, leading to carcinogenesis. Inhibiting the aberrant PTK function could inhibit tumor growth. Therefore, tyrosine kinase inhibitors (TKIs), target-specific inhibitors of PTKs, have been used in treating malignant tumors and play a significant role in targeted therapy of cancer. Currently, drug resistance is the main reason for limiting TKIs efficacy of cancer. The increasing studies indicated that tumor microenvironment, cell death resistance, tumor metabolism, epigenetic modification and abnormal metabolism of TKIs were deeply involved in tumor development and TKI resistance, besides the abnormal activation of PTK-related signaling pathways involved in gene mutations. Accordingly, it is of great significance to study the underlying mechanisms of TKIs resistance and find solutions to reverse TKIs resistance for improving TKIs efficacy of cancer. Herein, we reviewed the drug resistance mechanisms of TKIs and the potential approaches to overcome TKI resistance, aiming to provide a theoretical basis for improving the efficacy of TKIs.