Lysosomal pepstatin-insensitive proteinase as a novel biomarker for detecting and diagnosing breast cancer

A method of diagnosing breast cancer in a patient, comprising:

• (a) contacting a solid matrix having antibodies immunoreactive with CLN2p immobilized thereto with a patient's breast tissue sample or a vascular body fluid sample to allow CLN2p in the sample to bind to the immobilized antibodies;
• (b) removing unbound sample;
• (c) contacting the solid matrix with a labeled antibody specific for bound CLN2p;
• and
• (d) quantifying the amount of CLN2p in the patient's sample and comparing the amount obtained in (d) with the CLN2p amount in a normal, non-cancer control, wherein an increased amount of CLN2p in the patient's sample diagnoses breast cancer in the patient.

A method of diagnosing breast cancer by determining enzyme levels of CLN2p in a vascular fluid sample from an individual undergoing testing, comprising:

• a) acidifying the vascular fluid sample to a pH of about 3.0 to about 5.5;
• b) assaying the acidified sample for CLN2p activity;
• and
• c) comparing the CLN2p activity in the individual's test sample with CLN2p activity in a normal, noncancerous sample, wherein an increase in CLN2p activity in the test sample relative to CLN2p activity in the normal sample CLN2p diagnoses breast cancer.

A diagnostic system to detect CLN2p in a biological sample or vascular fluid, comprising:

• a) an anti-CLN2p specific antibody in an amount suitable for at least one assay for detecting the presence or amount of CLN2p, or fragment thereof, in a sample;
• b) instructions for use comprising a description of reagent concentration and/or at least one assay parameter selected from the group consisting of:
• relative amounts of reagent and sample to be admixed, maintenance time periods for reagent and sample admixtures, temperature and buffer conditions;
• and, optionally, c) a detectable label or indicating agent for signaling the formation of a complex of CLN2p, or bindable fragment thereof in the sample and the anti-CLN2p antibody.