Antibody-drug conjugates in cancer therapy: innovations, challenges, and future directions.

The emergence of antibody-drug conjugates (ADCs) as a potential therapeutic avenue in cancer treatment has garnered significant attention. By combining the selective specificity of monoclonal antibodies with the cytotoxicity of drug molecules, ADCs aim to increase the therapeutic index, selectively targeting cancer cells while minimizing systemic toxicity. Various ADCs have been licensed for clinical usage, with ongoing research paving the way for additional options. However, the manufacture of ADCs faces several challenges. These include identifying suitable target antigens, enhancing antibodies, linkers, and payloads, and managing resistance mechanisms and side effects. This review focuses on the strategies to overcome these hurdles, such as site-specific conjugation techniques, novel antibody formats, and combination therapy. Our focus lies on current advancements in antibody engineering, linker technology, and cytotoxic payloads while addressing the challenges associated with ADC development. Furthermore, we explore the future potential of personalized medicine, leveraging individual patients' molecular profiles, to propel ADC treatments forward. As our understanding of the molecular mechanisms driving cancer progression continues to expand, we anticipate the development of new ADCs that offer more effective and personalized therapeutic options for cancer patients.

Cell Death and the p53 Enigma During Mammalian Embryonic Development.

Twelve forms of programmed cell death (PCD) have been described in mammalian cells, but which of them occurs during embryonic development and the role played by the p53 transcription factor and tumor suppressor remains enigmatic. Although p53 is not required for mouse embryonic development, some studies conclude that PCD in pluripotent embryonic stem cells from mice (mESCs) or humans (hESCs) is p53-dependent whereas others conclude that it is not. Given the importance of pluripotent stem cells as models of embryonic development and their applications in regenerative medicine, resolving this enigma is essential. This review reconciles contradictory results based on the facts that p53 cannot induce lethality in mice until gastrulation and that experimental conditions could account for differences in results with ESCs. Consequently, activation of the G2-checkpoint in mouse ESCs is p53-independent and generally, if not always, results in noncanonical apoptosis. Once initiated, PCD occurs at equivalent rates and to equivalent extents regardless of the presence or absence of p53. However, depending on experimental conditions, p53 can accelerate initiation of PCD in ESCs and late-stage blastocysts. In contrast, DNA damage following differentiation of ESCs in vitro or formation of embryonic fibroblasts in vivo induces p53-dependent cell cycle arrest and senescence.

Developmental Acquisition of p53 Functions.

Remarkably, the p53 transcription factor, referred to as "the guardian of the genome", is not essential for mammalian development. Moreover, efforts to identify p53-dependent developmental events have produced contradictory conclusions. Given the importance of pluripotent stem cells as models of mammalian development, and their applications in regenerative medicine and disease, resolving these conflicts is essential. Here we attempt to reconcile disparate data into justifiable conclusions predicated on reports that p53-dependent transcription is first detected in late mouse blastocysts, that p53 activity first becomes potentially lethal during gastrulation, and that apoptosis does not depend on p53. Furthermore, p53 does not regulate expression of genes required for pluripotency in embryonic stem cells (ESCs); it contributes to ESC genomic stability and differentiation. Depending on conditions, p53 accelerates initiation of apoptosis in ESCs in response to DNA damage, but cell cycle arrest as well as the rate and extent of apoptosis in ESCs are p53-independent. In embryonic fibroblasts, p53 induces cell cycle arrest to allow repair of DNA damage, and cell senescence to prevent proliferation of cells with extensive damage.

Mutational screening of PKD1 and PKD2 in Indian ADPKD patients identified 95 genetic variants.

BACKGROUND: Mutation screening of autosomal dominant polycystic kidney disease (ADPKD) cases imply the major involvement of PKD1 mutations in 85% of patients while rest of the cases harbor mutation in PKD2, DNAJB11 and GANAB. This essentially indicates that individual's genotype holds the key for disease susceptibility and its severity. METHODS: For finding genetic variability underlying the disease pathophysiology, 84 Indian ADPKD cases, 31 family members (12 susceptible) and 122 age matched control were screened for PKD1 and PKD2 using Sanger sequencing, PCR-RFLP and ARMS-PCR. RESULTS: Genetic screening of Indian ADPKD cases revealed total 67 variants in PKD1 and 28 variants in PKD2. Among the identified variants in PKD1 and PKD2 genes, 35.79% were novel variants and 64.2% recurrent. Further, subcategorization of PKD1 variants showed 14 truncation/frameshift, 21 nonsynonymous, 25 synonymous and 7 intronic variants. Moreover, we observed 40 families with PKD1 pathogenic variants, 7 families with PKD2 pathogenic variants, 9 families with PKD1 & PKD2 pathogenic variants, and 26 families with PKD1/PKD2/PKD1-PKD2 non-pathogenic genetic variants. CONCLUSION: Present study represented genetic background of Indian ADPKD cases which will be helpful in disease management as well as finding the genetically matched donor for kidney transplant.

Detection and characterization of mosaicism in autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is an inherited, progressive nephropathy accounting for 4-10% of end stage renal disease worldwide. PKD1 and PKD2 are the most common disease loci, but even accounting for other genetic causes, about 7% of families remain unresolved. Typically, these unsolved cases have relatively mild kidney disease and often have a negative family history. Mosaicism, due to de novo mutation in the early embryo, has rarely been identified by conventional genetic analysis of ADPKD families. Here we screened for mosaicism by employing two next generation sequencing screens, specific analysis of PKD1 and PKD2 employing long-range polymerase chain reaction, or targeted capture of cystogenes. We characterized mosaicism in 20 ADPKD families; the pathogenic variant was transmitted to the next generation in five families and sporadic in 15. The mosaic pathogenic variant was newly discovered by next generation sequencing in 13 families, and these methods precisely quantified the level of mosaicism in all. All of the mosaic cases had PKD1 mutations, 14 were deletions or insertions, and 16 occurred in females. Analysis of kidney size and function showed the mosaic cases had milder disease than a control PKD1 population, but only a few had clearly asymmetric disease. Thus, in a typical ADPKD population, readily detectable mosaicism by next generation sequencing accounts for about 1% of cases, and about 10% of genetically unresolved cases with an uncertain family history. Hence, identification of mosaicism is important to fully characterize ADPKD populations and provides informed prognostic information.

Mutational screening of PKD2 gene in the north Indian polycystic kidney disease patients revealed 28 genetic variations.

Polycystic kidney disease (PKD) is a systemic disorder which adds majority of renal patients to end stage renal disease. Autosomal dominant polycystic kidney disease (ADPKD) is more prevalent and leading cause of dialysis and kidney transplant. Linkage analysis revealed some closely linked loci, two of which are identified as PKD1, PKD2 and an unidentified locus to ADPKD. This study was performed using PCR and automated DNA sequencing in 84 cases and 80 controls to test potential candidature of PKD2 as underlying cause of PKD by in silico and statistical analyses. Two associated symptoms, hypertension (19%) and liver cyst (31%) havemajor contribution to PKD. Gender-based analysis revealed that familial female patients (27%) and familialmale patients (33%) are more hypertensive. Liver cyst, the second major contributing symptom presented by large percentage of sporadic males (46%). Genetic screening of all 15 exons of PKD2 revealed eight pathogenic (c.854_854delG, c.915C>A, c.973C>T, c.1050_1050delC, c.1604_1604delT, c.1790T>C, c.2182_2183delAG, c.2224C>T) and eight likely pathogenic (g.11732A>G, c.646T>C, c.1354A>G, g.39212G>C, c.1789C>A, c.1849C>A, c.2164G>T, c.2494A>G)DNA sequence variants. In our study, 27.38% (23/84) cases shown pathogenic / likely pathogenic variants in PKD2 gene. Some regions of PKD2 prone for genetic variation suggested to be linked with disease pathogenesis. This noticeable hot spot regions hold higher frequency (50%) of pathogenic / likely pathogenic genetic variants constituting single nucleotide variants than large deletion and insertion that actually represents only 41.08% of coding sequence of PKD2. Statistically significant association for IVS3-22AA genotype was observed with PKD, while association of IVS4+62C>T was found insignificant.