Biology subjects

Tipton, A. R.

Publications and source records attributed to Tipton, A. R..

4 recordsLinked to original sources

bioRxiv2023

Neratinib Synergizes with Trastuzumab Antibody Drug Conjugate or with Vinorelbine to Treat HER2 Mutated Breast Cancer Patient Derived Xenografts and Organoids.

HER2 (ERBB2) is a major therapeutic drug target in breast cancer and The Cancer Genome Atlas (TCGA) Breast Cancer project and other studies have identified HER2 activating mutations in breast cancers without HER2 gene amplification. HER2 activating mutations occur in 2-5% of metastatic breast cancer patients (MBC), and clinical trials have shown that the irreversible pan-HER tyrosine kinase inhibitor, neratinib, produces a 31-40% clinical benefit rate for HER2 mutated MBC patients. We developed breast cancer patient-derived xenografts (PDX) from ER+, HER2 mutated MBC patients and used them to test neratinib-based drug combinations. Using organoid culture of these PDX breast cancer cells, we performed rapid, high-throughput ex vivo screening assays to test novel drug combinations. These organoid culture experiments identified drug synergy with the neratinib plus ado-trastuzumab emtansine (T-DM1) and neratinib plus vinorelbine combinations and we validated these results with in vivo PDX experiments. Statement of SignificancePDXs are a ready source of human cancer organoids, and with thousands of PDXs already available worldwide, PDX derived organoids (PDxOs) can dramatically accelerate cancer drug testing. This strategy of PDxO drug testing is particularly useful for rare cancer subtypes or mutations to identify the most promising treatment strategies for clinical trials testing.

cancer biology↗

bioRxiv2022

Breast cancer mutations HER2 V777L and PIK3CA H1047R activate the p21/CDK4/6/Cyclin D1 axis driving tumorigenesis and drug resistance.

In metastatic breast cancer, HER2 activating mutations frequently co-occur with mutations in the PIK3CA, TP53, or E-cadherin genes. Of these co-occurring mutations, HER2 and PIK3CA mutations are the most prevalent gene pair, with approximately 40% of HER2 mutated breast cancers also having activating mutations in PIK3CA. To study the effects of co-occurring HER2 and PIK3CA mutations, we bred genetically engineered mice with the HER2V777L; PIK3CAH1047Rtransgenes (HP mice) and studied the resulting breast cancers both in vivo as well as ex vivo using cancer organoids. HP breast cancers show accelerated tumor formation in vivo and increased invasion and migration in in vitro assays. HP breast cancers have resistance to the pan-HER tyrosine kinase inhibitor, neratinib, but are effectively treated by neratinib plus trastuzumab deruxtecan. Proteomic and RNA-Seq analysis of HP breast cancers showed increased gene expression of Cyclin D1 and p21WAF1/Cip1 and changes in cell cycle markers. Combining neratinib with CDK4/6 inhibitors was another effective strategy for HP breast cancers with neratinib plus palbociclib showing a statistically significant reduction in mouse HP tumors as compared to either drug alone. We validated both the neratinib plus trastuzumab deruxtecan and neratinib plus palbociclib combinations using a human breast cancer patient-derived xenograft that has very similar HER2 and PIK3CA mutations. Both of these drug combinations are being tested in phase 1 clinical trials and this study provides valuable preclinical evidence for them.

cancer biology↗

bioRxiv2020

Mps1 promotes poleward chromosome movements in meiotic pro-metaphase

In prophase of meiosis I, homologous partner chromosomes pair and become connected by crossovers. Chiasmata, the connections formed between the partners enable the chromosome pair, called a bivalent, to attach as a single unit to the spindle. When the meiosis I spindle forms in prometaphase, most bivalents are associated with a single spindle pole and go through a series of oscillations on the spindle, attaching to and detaching from microtubules until the partners of the bivalent are bi-oriented, that is, attached to microtubules from opposite sides of the spindle, and prepared to be segregated at anaphase I. The conserved, kinetochore-associated kinase, Mps1, is essential for the bivalents to be pulled by microtubules across the spindle in prometaphase. Here we show that MPS1 is not required for kinetochores to attach microtubules but instead is necessary to trigger the migration of microtubule-attached kinetochores towards the poles. Our data support the model that Mps1 triggers depolymerization of microtubule ends once they attach to kinetochores in prometaphase. Thus, Mps1 acts at the kinetochore to co-ordinate the successful attachment of a microtubule and the triggering of microtubule depolymerization to move the chromosome.

cell biology↗

bioRxiv2019

Complexities of Microtubule Population Dynamics within the Mitotic Spindle

The microtubules of the mitotic spindle mediate chromosome alignment to the metaphase plate, then sister chromatid segregation to the spindle poles in anaphase. Previous analyses of spindle microtubule kinetics utilizing fluorescence dissipation after photoactivation described two main populations, a slow and a fast turnover population, and these were ascribed to reflect kinetochore versus non-kinetochore microtubules, respectively. Here, we test this categorization by disrupting kinetochores through depletion of the Ndc80 complex. In the absence of functional kinetochores, microtubule dynamics still exhibit slow and fast turnover populations, though the proportion of each population and the timings of turnover are altered. Importantly, the data obtained following Hec1/Ndc80 depletion suggests other sub-populations, in addition to kinetochore microtubules, contribute to the slow turnover population. Further manipulation of spindle microtubules revealed a complex landscape. Dissection of the dynamics of microtubule populations provides a greater understanding of mitotic spindle kinetics and insight into roles in facilitating chromosome attachment, movement, and segregation during mitosis.

cell biology↗