Tamoxifen side effects, age-related macular degeneration (AMD) or cancer associated retinopathy (CAR)?

Tamoxifen toxicity in cultured retinal pigment epithelial cells is mediated by concurrent regulated cell death mechanisms

PURPOSE

To evaluate the mechanism of tamoxifen-induced cell death in human cultured RPE cells, and to investigate concurrent cell death mechanisms including pyroptosis, apoptosis, and necroptosis.

METHODS

Human RPE cells were cultured until confluence and treated with tamoxifen; cell death was measured by detecting LDH release. Tamoxifen-induced cell death was further confirmed by 7-aminoactinomycin D (7-AAD) and annexin V staining. Lysosomal destabilization was assessed using lysosomal-associated membrane protein-1 (LAMP-1) and acridine orange staining. The roles of lysosomal enzymes cathepsin B and L were examined by blocking their activity. Caspase activity was evaluated by caspase-1, -3, -8, and -9 specific inhibition. Cells were primed with IL-1α and treated with tamoxifen; mature IL-1β production was quantified via ELISA. Caspase activity was verified with the fluorochrome-labeled inhibitor of caspases (FLICA) probe specific for each caspase. Regulated cell necrosis or necroptosis was examined with 7-AAD and inhibition of receptor-interacting protein 1 (RIP1) kinase using necrostatin-1 (Nec-1).

RESULTS

Cell death occurred within 2 hours of tamoxifen treatment of confluent RPE cells and was accompanied by lysosomal membrane permeabilization. Blockade of cathepsin B and L activity led to a significant decrease in cell death, indicating that lysosomal destabilization and cathepsin release occur prior to regulated cell death. Tamoxifen-induced toxicity was shown to occur through both caspase-dependent and caspase-independent cell death pathways. Treatment of RPE cells with caspase inhibitors and Nec-1 resulted in a near complete rescue from cell death.

CONCLUSIONS

Tamoxifen-induced cell death occurs through concurrent regulated cell death mechanisms. Simultaneous inhibition of caspase-dependent and caspase-independent cell death pathways is required to protect cells from tamoxifen. Inhibition of upstream activators, such as the cathepsins, may represent a novel approach to block multiple cell death pathways.

Multifocal electroretinography, color discrimination and ocular toxicity in tamoxifen use

PURPOSE

To study prospectively retinal function, color discrimination, and ocular toxicity in women treated with standard-dosage tamoxifen for breast cancer.

METHODS

Thirty visually asymptomatic patients with at least 2 years of continuous tamoxifen therapy underwent multifocal electroretinography (ERG), color discrimination testing, and ophthalmic examination. The results were compared with 17 patients who were not taking tamoxifen after breast cancer surgery and to an additional age-matched group of 21 healthy women.

RESULTS

Multifocal electroretinogram amplitudes and latencies were comparable among the three studied groups, and individual recordings were within age norms from our own lab. In the treated group, mild diffuse color vision loss was found in two patients with normal fundi. Three other patients had ocular toxic effects, with two cases of refractile retinal crystals and one case of keratopathy.

CONCLUSIONS

The aspects of central retinal function that are assessed by multifocal ERG were not affected even after at least 2 years of tamoxifen use, suggesting that the multifocal ERG is not sufficiently sensitive to detect tamoxifen-associated change that might occur. Some degree of color vision loss and ocular toxic effects were found in a few cases of this cohort suggesting that women using tamoxifen should receive an eye exam at least as often as recommended for middle-aged people.

The clinical applications of multifocal electroretinography: a systematic review

Multifocal electroretinography (mfERG) is an investigation that can simultaneously measure multiple electroretinographic responses at different retinal locations by cross-correlation techniques. mfERG therefore allows topographic mapping of retinal function in the central 40-50 degrees of the retina. The strength of mfERG lies in its ability to provide objective assessment of the central retinal function at different retinal areas within a short duration of time. Since the introduction of mfERG in 1992, mfERG has been applied in a large variety of clinical settings. This article reviews the clinical applications of mfERG based on the currently available evidence. mfERG has been found to be useful in the assessment of localized retinal dysfunction caused by various acquired or hereditary retinal disorders. The use of mfERG also enabled clinicians to objectively monitor the treatment outcomes as the changes in visual functions might not be reflected by subjective methods of assessment. By changing the stimulus, recording, and analysis parameters, investigation of specific retinal electrophysiological components can be performed topographically. Further developments and consolidations of these parameters will likely broaden the use of mfERG in the clinical setting.

Tamoxifen therapy conveys increased risk of developing a macular hole

PURPOSE

To determine etiological factors in the development of, as well as anatomic success rate and visual outcome of a large consecutive series of macular hole surgeries.

METHODS

Retrospective analysis of 300 consecutive cases of macular hole surgery by a single surgeon (RDB) between 1999 and 2003. Patients' medical and surgical histories were recorded and analysed for factors involved in aetiology and visual outcome.

RESULTS

There were 8 (4.12%) women, on tamoxifen in the study, two of these women had bilateral macular holes. When this study prevalence of tamoxifen therapy (4.12%) was compared to the estimated percentage of women in the same age group in the Australian population on tamoxifen (0.82%), a statistically significant difference (p value 0.0001) was found. Analysis of the number of bilateral holes in the tamoxifen group compared to the non-tamoxifen group was suggestive of an increased incidence of bilateral holes but not to a significantly significant degree.

CONCLUSION

Whilst no published reports link tamoxifen and macular holes, this may be due to the low incidence of the condition. Our study demonstrates a strong link between tamoxifen use and macular holes. Patients being commenced on tamoxifen should be advised of possible ocular complications and receive prompt ophthalmic review if symptoms develop.