Elevated FSP1 protects KRAS-mutated cells from ferroptosis during tumor initiation

Oncogenic KRAS is the key driver oncogene for several of the most aggressive human cancers. One key feature of oncogenic KRAS expression is an early increase in cellular reactive oxygen species (ROS) which promotes cellular transformation if cells manage to escape cell death, mechanisms of which remain incompletely understood. Here, we identify that expression of oncogenic as compared to WT KRAS in isogenic cellular systems renders cells more resistant to ferroptosis, a recently described type of regulated necrosis. Mechanistically, we find that cells with mutant KRAS show a specific lack of ferroptosis-induced lipid peroxidation. Interestingly, KRAS-mutant cells upregulate expression of ferroptosis suppressor protein 1 (FSP1). Indeed, elevated levels of FSP1 in KRAS-mutant cells are responsible for mediating ferroptosis resistance and FSP1 is upregulated as a consequence of MAPK and NRF2 pathway activation downstream of KRAS. Strikingly, FSP1 activity promotes cellular transformation in soft agar and its overexpression is sufficient to promote spheroid growth in 3D in KRAS WT cells. Moreover, FSP1 expression and its activity in ferroptosis inhibition accelerates tumor onset of KRAS WT cells in the absence of oncogenic KRAS in vivo. Consequently, we find that pharmacological induction of ferroptosis in pancreatic organoids derived from the LsL-KRAS^G12D expressing mouse model is only effective in combination with FSP1 inhibition. Lastly, FSP1 is upregulated in non-small cell lung cancer (NSCLC), colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC) as compared to the respective normal tissue of origin and correlates with NRF2 expression in PDAC patient datasets. Based on these data, we propose that KRAS-mutant cells must navigate a ferroptosis checkpoint by upregulating FSP1 during tumor establishment. Consequently, ferroptosis-inducing therapy should be combined with FSP1 inhibitors for efficient therapy of KRAS-mutant cancers.

Ferroptosis response segregates small cell lung cancer (SCLC) neuroendocrine subtypes

Loss of TP53 and RB1 in treatment-naïve small cell lung cancer (SCLC) suggests selective pressure to inactivate cell death pathways prior to therapy. Yet, which of these pathways remain available in treatment-naïve SCLC is unknown. Here, through systemic analysis of cell death pathway availability in treatment-naïve SCLC, we identify non-neuroendocrine (NE) SCLC to be vulnerable to ferroptosis through subtype-specific lipidome remodeling. While NE SCLC is ferroptosis resistant, it acquires selective addiction to the TRX anti-oxidant pathway. In experimental settings of non-NE/NE intratumoral heterogeneity, non-NE or NE populations are selectively depleted by ferroptosis or TRX pathway inhibition, respectively. Preventing subtype plasticity observed under single pathway targeting, combined treatment kills established non-NE and NE tumors in xenografts, genetically engineered mouse models of SCLC and patient-derived cells, and identifies a patient subset with drastically improved overall survival. These findings reveal cell death pathway mining as a means to identify rational combination therapies for SCLC.

Experimental increase in accommodative potential after neodymium: yttrium-aluminum-garnet laser photodisruption of paired cadaver lenses

PURPOSE

Loss of lens elasticity is one of several proposed mechanisms responsible for the decline in accommodation with age and is the most accepted explanation for presbyopia. We wish to confirm the lens elasticity premise and attempt to experimentally reverse the age-dependent loss of accommodative potential as measured by polar strain.

DESIGN

Experimental human autopsy eye study.

PARTICIPANTS AND CONTROLS

Thirty-six cadaver lenses were tested to determine the age-dependent polar strain. Eleven lens pairs were then tested with one lens treated with neodymium:yttrium-aluminum-garnet (Nd:YAG) laser and the other left untreated before rotation as an age control.

TESTING

Using a custom-made rotational apparatus (described by Fisher, 1971), freshly excised cadaver lenses (<48 hours postmortem) were rotated at 1000 rpm on a 9-mm diameter pedestal to simulate the physiologic pull of the zonules. Lenses were initially tested to determine the age-dependent polar strain. One lens in a pair was then treated with an Nd:YAG laser and the other left untreated before testing. Treatment consisted of 100 suprathreshold pulse placed in a central annular pattern of 2- to 4-mm diameter. Treatment energies varied from 2.5 to 7.0 mJ/pulse, depending on the relative clarity of the lenses. Polar strain was both microscopically measured and calculated from projected photographs before and after rotation of both lased and unlased lenses. Statistically significant differences were determined by paired t test.

MAIN OUTCOME MEASURES

Polar strain (decrease in axial thickness with rotation) of the lens.

RESULTS

An age-dependent decrease in polar strain was observed that paralleled the findings of Fisher. Both measured and projected polar strain were greater in the lased than unlased lens, and this difference was highly significant by paired t test (P = 0.001 and P = 0.004, respectively).

CONCLUSIONS

Age-dependent loss of lens elasticity (polar strain) can be experimentally reversed (increased) by selective intralenticular photodisruption.

Doppler-derived aortic flow measurements during and after heavy isometric exercise in healthy men versus men with myocardial infarction

Doppler echocardiography is a useful noninvasive determination of left ventricular function during dynamic exercise. Scarce data are available for the use of this technique during heavy isometric exercise. Therefore, Doppler-derived aortic flow indexes were assessed during and after 50% maximal upper-body isometric exercise in 25 healthy men (aged 47 +/- 6 years) and compared with those of 22 men (aged 48 +/- 9 years) who had suffered myocardial infarction. The heart rate increased (p = 0.01) in each of the groups from a mean of 68 +/- 12 at rest to 84 +/- 11 during isometric exercise. At rest, systolic blood pressure was higher (p = 0.05) in the patients with coronary artery disease. During exercise, the patients with cardiac disease, compared with the healthy volunteers, demonstrated a lesser reduction in flow velocity integral, stroke volume, and cardiac indexes (p = 0.001). Immediately on recovery, the patients with cardiac disease, compared with the healthy group, showed significantly greater (p = 0.001) increase in stroke volume and cardiac indexes. At 3 minute's recovery, the stroke volume index continued to increase in the patients with cardiac disease, while the healthy group showed a decrease to below its resting value. Although 50% of maximal upper-body isometric exercise caused similar heart rate and systolic blood pressure responses in healthy patients and patients with cardiac disease, there were significant group differences in Doppler-derived left ventricular systolic function indexes, which were greatest on immediate and 3 minute's recovery. The results suggest that this novel isometric test may be useful in clinical testing.

Twice-daily administration of oral verapamil in the treatment of essential hypertension

The antihypertensive effect of twice-daily administration of verapamil hydrochloride was evaluated in 21 adult patients with mild to moderate essential hypertension. Following four weeks of placebo therapy, verapamil was given for four weeks with a treatment goal of sitting diastolic blood pressure (BP) of less than 90 mm Hg, or to a maximum dose of 160 mg twice daily. Sitting and standing BPs, heart rate, and verapamil plasma levels were determined weekly, ten to 12 hours post dose. At the maximal dose (mean, 154 +/- 19.2 mg), heart rate was not affected, side effects were minimal, and sitting diastolic BP was significantly reduced from placebo baseline, with 12 of 21 patients having a fall in sitting diastolic BP of 10 mm Hg or more or less than 90 mm Hg. A trough verapamil plasma level of greater than 80 ng/mL was associated with a good hypotensive response. These data indicate the safety and utility of twice-daily verapamil administration for the treatment of essential hypertension and suggest the value of obtaining verapamil plasma levels as a guide to dosage determination.

Comparison of diltiazem and nifedipine for both angina pectoris and systemic hypertension

In a randomized, double-blind, placebo-controlled crossover trial, diltiazem and nifedipine were compared in 10 patients with stable angina pectoris and mild to moderate hypertension (supine diastolic blood pressure greater than or equal to 90 mm Hg). Patients received placebo for 2 weeks, then increasing doses of diltiazem (90 to 360 mg/day) or nifedipine (30 to 120 mg/day) in 3 daily divided doses over 2 weeks, followed by 1 week of therapy at the maximal dose, a 1-week placebo "washout," then crossover to the other drug. Heart rate and blood pressure at rest and during exercise, anginal frequency, nitroglycerin consumption and treadmill exercise tolerance were assessed. Compared with placebo, anginal frequency and nitroglycerin consumption were reduced with both diltiazem and nifedipine (p less than 0.01) and exercise tolerance was increased with both drugs (p less than 0.01). Standing blood pressure at rest was reduced by diltiazem and nifedipine (146.6 +/- 11.4/97.7 +/- 5.3 mm Hg at placebo, baseline reduced to 129.6 +/- 15.2/79.5 +/- 13.7 mm Hg with diltiazem, and to 122.2 +/- 9.9/82.0 +/- 7.1 with nifedipine, p less than 0.01 for both). Compared with placebo, diltiazem and nifedipine also reduced exercise diastolic blood pressure (p less than 0.01), but not systolic blood pressure. Diltiazem lowered the heart rate at rest from 88.5 +/- 14.4 beats/min at placebo baseline to 79.7 +/- 17.9 beats/min (p less than 0.01); the heart rate with diltiazem was 11 beats/min lower than that with nifedipine (p less than 0.05). Both diltiazem and nifedipine had similar effects on the heart rate-blood pressure product at rest and during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)