Lysosomal membrane permeabilization (LMP) contributes to tissue involution, degenerative diseases, and cancer therapy. Its investigation has, however, been hindered by the lack of sensitive methods. Here, we characterize and validate the detection of galectin puncta at leaky lysosomes as a highly sensitive and easily manageable assay for LMP. LGALS1/galectin-1 and LGALS3/galectin-3 are best suited for this purpose due to their widespread expression, rapid translocation to leaky lysosomes and availability of high-affinity antibodies. Galectin staining marks individual leaky lysosomes early during lysosomal cell death and is useful when defining whether LMP is a primary or secondary cause of cell death. This sensitive method also reveals that cells can survive limited LMP and confirms a rapid formation of autophagic structures at the site of galectin puncta. Importantly, galectin staining detects individual leaky lysosomes also in paraffin-embedded tissues allowing us to demonstrate LMP in tumor xenografts in mice treated with cationic amphiphilic drugs and to identify a subpopulation of lysosomes that initiates LMP in involuting mouse mammary gland. The use of ectopic fluorescent galectins renders the galectin puncta assay suitable for automated screening and visualization of LMP in live cells and animals. Thus, the lysosomal galectin puncta assay opens up new possibilities to study LMP in cell death and its role in other cellular processes such as autophagy, senescence, aging, and inflammation.

BACKGROUND Neoantigen-driven recognition and T cell–mediated killing contribute to tumor clearance following adoptive cell therapy (ACT) with tumor-infiltrating lymphocytes (TILs). Yet how diversity, frequency, and persistence of expanded neoepitope-specific CD8 + T cells derived from TIL infusion products affect patient outcome is not fully determined. METHODS Using barcoded pMHC multimers, we provide a comprehensive mapping of CD8 + T cells recognizing neoepitopes in TIL infusion products and blood samples from 26 metastatic melanoma patients who received ACT. RESULTS We identified 106 neoepitopes within TIL infusion products corresponding to 1.8% of all predicted neoepitopes. We observed neoepitope-specific recognition to be virtually devoid in TIL infusion products given to patients with progressive disease outcome. Moreover, we found that the frequency of neoepitope-specific CD8 + T cells in TIL infusion products correlated with increased survival and that neoepitope-specific CD8 + T cells shared with the infusion product in posttreatment blood samples were unique to responders of TIL-ACT. Finally, we found that a transcriptional signature for lymphocyte activity within the tumor microenvironment was associated with a higher frequency of neoepitope-specific CD8 + T cells in the infusion product. CONCLUSIONS These data support previous case studies of neoepitope-specific CD8 + T cells in melanoma and indicate that successful TIL-ACT is associated with an expansion of neoepitope-specific CD8 + T cells. FUNDING NEYE Foundation; European Research Council; Lundbeck Foundation Fellowship; Carlsberg Foundation.

Proton pump inhibitors (PPIs) are commonly used as a supplement to cancer therapy. Yet, their effect on cancer mortality is largely unknown. Using data from Danish nationwide registries and Cox models regressing of both propensity scores and drug use, we estimated hazard ratios (HRs) with 95% confidence intervals (CIs) for cancer-specific and noncancer death among PPI users (≥2 prescriptions within six months after diagnosis; n = 36,066) compared with nonusers (<2 prescriptions, n = 311,853) or users of histamine H -receptor antagonists (H RA; n = 5,152). Adjusted HRs for cancer-specific mortality among postdiagnostic PPI users as compared with nonusers or H RA users were 1.29 (95% CI, 1.27-1.32) and 1.15 (95% CI, 1.10-1.20), respectively. HRs for cancer mortality associated with PPI use were highest for ovarian (1.35; 95% CI, 1.20-1.52) and lowest for esophageal cancer (0.91; 95% CI, 0.81-1.04). The associations were stronger among new PPI users after cancer diagnosis, indicating potential confounding. To test the effect of PPIs on tumor growth in a model system free for confounding factors, we investigated the effect of pantoprazole on tumor growth in mice. Pantoprazole (5 mg/kg/day) enhanced tumor growth (p = 0.033) and reduced the antitumor activity of gemcitabine (p = 0.008) in fibrosarcoma-bearing Balb/c mice, but not in immunodeficient Balb/c nude mice. In breast carcinoma-bearing FVB/N mice, pantoprazole had no effect on tumor growth alone but it reduced the life-prolonging effect of doxorubicin significantly (p = 0.007). Taken together, these data raise concerns about the increasing use of PPIs and calls for further studies addressing their safety among cancer patients.

HER2/ErbB2 activation turns on transcriptional processes that induce local invasion and lead to systemic metastasis. The early transcriptional changes needed for ErbB2-induced invasion are poorly understood. Here, we link ErbB2 activation to invasion via ErbB2-induced, SUMO-directed phosphorylation of a single serine residue, S27, of the transcription factor Myeloid Zinc Finger-1 (MZF1). Utilizing an antibody against MZF1-pS27, we show that the phosphorylation of S27 correlates significantly (p<0.0001) with high-level expression of ErbB2 in primary invasive breast tumors. Phosphorylation of MZF1-S27 is an early response to ErbB2 activation and results in increased transcriptional activity of MZF1. It is needed for the ErbB2-induced expression of MZF1 target genes CTSB and PRKCA, and invasion of single-cells from ErbB2-expressing breast cancer spheroids.The phosphorylation of MZF1-S27 is preceded by poly-SUMOylation of K23, which can make S27 accessible to efficient phosphorylation by PAK4. Based on our results, we suggest for an activation mechanism where phosphorylation of MZF1-S27 triggers MZF1 dissociation from its transcriptional repressors, such as the CCCTC-binding factor (CTCF). Our findings increase understanding of the regulation of invasive signaling in breast cancer by uncovering a detailed biological mechanism of how ErbB2 activation can rapidly lead to its invasion-promoting target gene expression and invasion.