Purpose
Patients with anaplastic lymphoma kinase (ALK) gene rearrangements often manifest dramatic responses to crizotinib, a small molecule ALK inhibitor. Unfortunately, not every patient responds and acquired drug resistance inevitably develops in those that do respond. This study aimed to define molecular mechanisms of resistance to crizotinib in ALK+ non-small cell lung cancer (NSCLC) patients.
Experimental Design
We analyzed tissue obtained from 14 ALK+ NSCLC patients demonstrating evidence of radiologic progression while on crizotinib in order to define mechanisms of intrinsic and acquired resistance to crizotinib.
Results
Eleven patients had material evaluable for molecular analysis. Four patients (36%) developed secondary mutations in the tyrosine kinase domain of ALK. A novel mutation in the ALK kinase domain, encoding a G1269A amino acid substitution that confers resistance to crizotinib in vitro, was identified in two of these cases. Two patients, one with a resistance mutation, exhibited new onset ALK copy number gain (CNG). One patient demonstrated outgrowth of EGFR mutant NSCLC without evidence of a persistent ALK gene rearrangement. Two patients exhibited a KRAS mutation, one of which occurred without evidence of a persisting ALK gene rearrangement. One patient demonstrated the emergence of an ALK gene fusion negative tumor compared to the baseline sample, but with no identifiable alternate driver. Two patients retained ALK positivity with no identifiable resistance mechanism.
Conclusions
Crizotinib resistance in ALK+ NSCLC occurs through somatic kinase domain mutations, ALK gene fusion CNG, and emergence of separate oncogenic drivers.
Summary
Understanding gut microbiota alterations associated with HIV-infection and factors that drive these alterations may help explain gut-linked diseases prevalent with HIV. 16S rRNA sequencing of feces from HIV infected individuals revealed that HIV infection is associated with highly characteristic gut community changes and antiretroviral therapy does not consistently restore the microbiota to an HIV-negative state. Despite the chronic gut inflammation characteristic of HIV infection, the associated microbiota showed limited similarity with other inflammatory states and instead showed increased, rather than decreased, diversity. Metaanalysis revealed that the microbiota of HIV-infected individuals in the US was most similar to a Prevotella-rich community composition typically observed in healthy individuals in agrarian cultures of Malawi and Venezuela and related to that of US individuals with carbohydrate-rich/ protein- and fat-poor diets. By evaluating innate and adaptive immune responses to lysates from bacteria that differ with HIV, we explore the functional drivers of these compositional differences.
Rationale: Efficient removal of apoptotic cells is essential for the resolution of acute pulmonary inflammation. Alveolar macrophages ingest apoptotic cells less avidly than other professional phagocytes at rest but overcome this defect during acute inflammation. Surfactant protein (SP)-A and SP-D are potent modulators of macrophage function and may suppress clearance of apoptotic cells through activation of the transmembrane receptor signal inhibitory regulatory protein a (SIRPa). Objectives: To investigate whether binding of SP-A and SP-D to SIRPa on alveolar macrophages suppresses apoptotic cell clearance. Methods: Phagocytosis of apoptotic cells was assessed using macrophages pretreated with SP-A, SP-D, or the collectin-like molecule C1q. Binding of SP-A and SP-D to SIRPa was confirmed in vitro using blocking antibodies and fibroblasts transfected with active and mutant SIRPa. The effects of downstream molecules SHP-1 and RhoA on phagocytosis were studied using SHP-1-deficient mice, sodium stibogluconate, and a Rho kinase inhibitor. Lipopolysaccharide was given to chimeric mice to study the effects of SP-A and SP-D binding on inflammatory macrophages.
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