Sequential treatment with targeted therapies can result in complex combinations of resistance mutations in drug targets. To establish the origins of resistance mutations, Schmitt and colleagues integrated single-molecule duplex sequencing of Philadelphia-positive leukemias with computational simulations. A combination of drug target mutation burden and tumor-initiating cell fraction predicts the likelihood of preexisting resistance mutations. Compound resistance is unlikely to exist before therapy, but rather is predicted to arise following the failure of first-generation therapies. The results predict that front-line use of pan-target therapies (i.e., therapies that can overcome any single resistance mutation) could improve outcomes.Correlation of HER2 expression to therapeutic resistance was previously investigated on ex vivo models by others. To explore the role of dynamic status of HER2 on tumor cells, Li and colleagues performed HER2-iFISH to longitudinally examine constant variation of HER2 phenotype and chromosome aneuploidy in CTCs in gastric cancer patients. Comparing to low positivity of histopathologic detection of HER2 in tumor mass, significantly higher positivity (>70%) of HER2 expression on aneuploid CTCs was demonstrated, which was relevant to developing resistance to the targeted and/or chemotherapy and thus shows promise to monitor developing therapeutic resistance in real time.Anti-PD-1/PD-L1-based immunotherapies can be transformative in a subset of metastatic cancer patients, but reliable biomarkers of response have been elusive. To integrate biomarkers of efficacy in clinical practice, Johnson and colleagues performed quantitative, multiplexed immunofluorescence tests comprised of HLA-DR, IDO-1, PD-1, and PD-L1 utilizing novel AQUA algorithms on archival, pre-treatment samples from 166 metastatic melanoma patients treated with PD-1 blockers across ten cancer centers. Biomarker signature-positive patients experienced superior survival and response rates in both discovery and validation cohorts. This two-slide assay on archival tissue may help identify patients who will have excellent outcomes with anti-PD-1 therapy.Pancreatic cancer is one of the biggest clinical challenges. Zhou and colleagues used a combination of local photothermal therapy and intratumoral application of an immunoadjuvant to treat a metastatic pancreatic tumor in mice, both subcutaneously and orthotopically. This unique combination significantly prolonged the animal survival time and slowed and, in many cases, prohibited the distant metastases. It also induced a long-term, tumor-specific immunity by increasing the quantity and quality of splenic and tumor-infiltrating antitumor T cells. This novel approach with its successful treatment results, particularly on orthotopic pancreatic tumors, shows promise as a clinical treatment modality for pancreatic cancer patients.