Reviews & Analysis

Achieving depletion of regulatory T cells while sparing tumor-specific effector T cells has long remained an elusive goal of immunotherapy. A new study describing the development of an antibody to the cytokine receptor CD25 optimized to ensure depletion of regulatory T cells without blocking binding of the cytokine IL-2 will reinvigorate interest in this therapeutic avenue.

The response to immunotherapy has been linked to human leukocyte antigen (HLA) genotype in certain cancers. A new study examining the interaction between cancer type–specific mutational exposures and the B44 and B27 HLA supertypes finds that patients with mutant peptides complementary to these supertypes receive the most benefit from immune-checkpoint blockade.

Immunostimulatory agents such as Toll-like receptor (TLR) agonists have shown promising antitumor efficacy but are associated with therapy-related toxicities when delivered systemically. Immune-stimulating antibody conjugates are now shown to deliver TLR agonists with potent preclinical antitumor activities.

Invariant natural killer T cells (iNKT cells) are innate-like CD1d-restricted T cells that have NK cell–like properties and bear an invariant T cell receptor (iTCR). iNKT cells have shown potential for cancer immunotherapy. A study now shows that stabilization of the iTCR–CD1d complex via a single-chain bi-specific antibody stimulates iNKT cell–mediated anti-tumor immunity.

Tumor-specific changes in DNA methylation are both acquired actively through transcription-coupled processes and passively accumulated over time. Analysis across B cell malignancies now shows that these changes provide insight into the cellular origin as well as the proliferative history of tumors and thereby have diagnostic value and prognostic value, respectively.

Mitochondrial DNA damage, metabolic disruption and aging have all been associated with cancer. These three threads are now woven together to show that aging-associated somatic mutations to mitochondrial DNA alter mitochondrial serine metabolism to support cell transformation and colon-cancer development.

Effective methods for treating retinoblastoma while preserving vision are an unmet clinical need. Subretinal delivery of a hydrogel containing T cells that secrete the cytokine IL-15 and express a chimeric antigen receptor directed at the ganglioside protein GD2 completely controls retinoblastoma in immunocompromised mice, with no obvious damage to the surrounding retina.

Cancer has found a formidable foil in COVID-19, and this has brought to the fore the early concerns that COVID-19 could have a deeper impact on oncology patients. Two studies now provide insights into the enigma surrounding the determinants of the worsening of COVID-19 symptoms in patients with cancer.

Immunotherapy has changed the treatment paradigm for patients with cancer, but patient selection, response assessment and treatment duration require further refinement. A recent study reports that the kinetics of circulating tumor DNA reflect response and resistance to immunotherapy treatment across multiple cancer types and could be used to tailor treatment.

The urea cycle enzyme argininosuccinate synthase 1 (ASS1) is upregulated in some cancer types. A study now shows that tumor cells with elevated urea cycle activity due to high ASS1 expression enhance gluconeogenesis, enabling a metabolic shift toward serine synthesis and causing purine synthesis addiction for growth and proliferation.

Replication stress fuels chromosomal instability, tumor heterogeneity and therapy resistance. The Sonic hedgehog pathway is now linked to an unorthodox form of replication stress in cerebellar granular-cell progenitors through deregulated firing of DNA replication origins, with implications for the pathogenesis, genomic instability and treatment of medulloblastoma.

Locally injected lipid nanoparticles that deliver RNA to elicit danger signals and simultaneously contain RNA that encodes a membrane-anchored version of the cytokine IL-12 can induce immunogenic cell death in tumors. This multipronged platform induces anticancer immune responses to the injected lesion as well as to distant tumors and hence produces an abscopal effect.

Deep learning can be used to predict genomic alterations on the basis of morphological features learned from digital histopathology. Two independent pan-cancer studies now show that automated learning from digital pathology slides and genomics can potentially delineate broader classes of molecular signatures and prognostic associations across cancer types.

The pre-metastatic niche is a complex microenvironment formed by the influence of tumor-derived factors on stromal and immune cells at distant sites of disseminated tumor-cell colonization. Signaling through the kinase p38α and regulation of the type I interferon receptor are now linked to formation of the pre-metastatic niche.

The approval of anti-TNF therapy for colitis over 20 years ago represented a paradigm shift for the treatment of this disease. Anti-TNF therapy is now shown to prevent colitis-associated colon cancer in mice by modifying the gut microbiota composition and transcriptional activity, including genes in Escherichia coli that control colibactin synthesis.

KEAP1 is a tumor suppressor encoded by a gene commonly mutated in lung cancer. A systematic search for Keap1-mutant cancer vulnerabilities now reveals that Slc33a1 is a context-specific essential gene that represents a promising new anti-cancer target.

Natural killer (NK) cells serve a critical role in the control of metastasis. NK cells are now shown to preferentially control monoclonal metastases derived from single circulating tumor cells rather than polyclonal metastases derived from cell clusters. These findings provide further evidence that NK cells are linked to metastatic cell immunoediting.

Immune-checkpoint blockade holds great promise in cancer therapy; however, T cell–specific checkpoint inhibitors are not effective for all patients with cancer. The transcription factor c-Rel is now shown to regulate pro-inflammatory polarization of myeloid cells and modulate anti-tumor immune responses.

Studies of the tumor microenvironment have provided fundamental insights into cancer progression. A new study now delineates the dynamics of immune-cell alterations at the single-cell level and across stages of multiple myeloma, elucidating the microenvironmental changes involved in the precursor states of the disease.

Small-cell lung cancer rapidly develops resistance to standard-of-care therapy. Two papers now establish xenograft models derived from patient-derived circulating tumor cells and show that initially homogeneous, chemoresponsive tumors rapidly recur as heterogeneous drug-refractory disease.