Inclusion Criteria:

- Confirmed pathological diagnosis of MCL according to WHO classification.

- Relapse or progression following 1 to 3 prior lines of anti-neoplastic standard
therapy. Therapy in remission after initial induction like intensified chemotherapy
for stem cell separation followed by myeloablative therapy or any kind of maintenance
therapy is classified as one line of therapy with the induction therapy..

- If Rituximab was part of prior treatment, documented time to progression must be at
least 12 weeks after this particular regimen.

- If high-dose Ara-C was part of prior treatment, documented time to progression must
be at least 6 months after this particular regimen.

- Patients relapsed after autologous stem cell transplantation or not appropriate for
myeloablative treatment.

- At least 1 measurable or assessable site of disease; in case of bone marrow
infiltration only, bone marrow aspiration/ biopsy is mandatory for all staging
evaluations.

- age > 18 years

- ECOG/WHO Performance Score 0-2 unless lymphoma related.

- The following laboratory values at screening, unless lymphoma related:

- Absolute neutrophil count (ANC) > = 1500 cells/microlitre

- Platelets > = 100,000 cells/microlitre

- Transaminases (AST and ALT) <=3 x upper limit of normal (ULN)

- Total bilirubin <=2 x ULN

- Creatinine <=2 mg/dL or calculated creatinine clearance >=50 mL/min

- Toxic effects of previous therapy or surgery resolved to NCI CTC grade 2 or better.

- Premenopausal fertile females must agree to use a highly effective method of birth
control for the duration of the therapy. A highly effective method of birth control
is defined as those which result in a low failure rate (i.e. less than 1% per year)
when used consistently and correctly such as implants, injectables, combined oral
contraceptives, some IUDs, sexual abstinence or vasectomised partner.

- Men must agree not to father a child for the duration of therapy and must agree to
advice a female partner to use a highly effective method of birth control.

- Written informed consent before performance of any study-related procedure.

Exclusion Criteria:

- Previous treatment with Bortezomib

- Treatment within another clinical trial within 30 days before trial entry or planned
during this trial

- Anti-neoplastic (including radiation and antibody treatment) or experimental therapy
within 4 weeks before planed Day 1 of Cycle 1 (Nitrosoureas within 6 weeks ) or
radioimmunoconjugates or toxin immunoconjugates such as Ibritumomab tiuxetan
(Zevalin™) or Tositumomab (Bexxar®) within 12 weeks before planed Day 1 of Cycle 1

- Known hypersensitivity to Rituximab, boron or mannitol.

- Active malignancy other than MCL within 5 years before Day 1 of Cycle 1, with the
exception of complete resection of basal cell carcinoma, squamous cell carcinoma of
the skin, or in situ malignancy.

- Active systemic infection requiring treatment.

- HIV, hepatitis B or C

- Patient has >= grade 2 peripheral sensory neuropathy or neuropathic pain defined by
the NCI Common Terminology Criteria for Adverse Events (CTCAE).

- Symptomatic degenerative or toxic encephalopathy

- Serious medical condition (such as severe hepatic impairment, pericardial disease,
acute diffuse infiltrative pulmonary disease, systemic infections etc) or psychiatric
illness likely to interfere with participation in this clinical study

- Female subject is pregnant or breast-feeding (pregnancy testing is mandatory for
premenopausal women).